new package modiagram (26sep11)

git-svn-id: svn://tug.org/texlive/trunk@24106 c570f23f-e606-0410-a88d-b1316a301751

9 files changed, 2895 insertions, 1 deletions

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+MOdiagram - easy creation of molecular orbital diagrams
+
+The environment 'MOdiagram' and some commands are provided to create
+molecular orbital (MO) diagrams using TikZ.
+
+The MO diagram of H2 would be set like:
+\begin{MOdiagram}
+ \atom{left}{ 1s = {0;up} }
+ \atom{right}{ 1s = {0;up} }
+ \molecule{ 1sMO = {1;pair, } }
+\end{MOdiagram}
+
+MOdiagram loads the packages 'expl3', 'xparse' and 'l3keys2e' and therefore
+needs LaTeX3 support as provided by the package bundles 'l3kernel' and
+'l3packages'.
+MOdiagram also needs the packages 'tikz', 'amsmath' and 'textgreek' as well as
+the tikzlibraries 'arrows' and 'calc' to be fully functioning.
+
+Clemens NIEDERBERGER
+2011/09/25
+
+http://www.mychemistry.eu/
+contact@mychemistry.eu
+
+If you have any ideas, questions, suggestions or bugs to report,
+please feel free to contact me.
+
+Copyright 2011 Clemens Niederberger
+
+This work may be distributed and/or modified under the
+conditions of the LaTeX Project Public License, either version 1.3
+of this license or (at your option) any later version.
+The latest version of this license is in
+  http://www.latex-project.org/lppl.txt
+and version 1.3 or later is part of all distributions of LaTeX
+version 2005/12/01 or later.
+
+This work has the LPPL maintenance status `maintained'.
+
+The Current Maintainer of this work is Clemens Niederberger.
+
+This work consists of the files modiagram.sty, modiagram_doc_de.tex,
+modiagram_doc_de.tex and README.
\ No newline at end of file
diff --git a/Master/texmf-dist/doc/latex/modiagram/modiagram_doc_de.pdf b/Master/texmf-dist/doc/latex/modiagram/modiagram_doc_de.pdf
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diff --git a/Master/texmf-dist/doc/latex/modiagram/modiagram_doc_de.tex b/Master/texmf-dist/doc/latex/modiagram/modiagram_doc_de.tex
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+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% --------------------------------------------------------------------------- %
+% - MOdiagram - modiagram_doc_de.tex                                        - %
+% - easy creation of molecular orbital diagrams                             - %
+% --------------------------------------------------------------------------- %
+% - Clemens NIEDERBERGER                                                    - %
+% - 2011/09/25                                                              - %
+% --------------------------------------------------------------------------- %
+% - http://www.mychemistry.eu/                                              - %
+% - contact@mychemistry.eu                                                  - %
+% --------------------------------------------------------------------------- %
+% - If you have any ideas, questions, suggestions or bugs to report, please - %
+% - feel free to contact me.                                                - %
+% --------------------------------------------------------------------------- %
+% - Copyright 2011 Clemens Niederberger                                     - %
+% -                                                                         - %
+% - This work may be distributed and/or modified under the                  - %
+% - conditions of the LaTeX Project Public License, either version 1.3      - %
+% - of this license or (at your option) any later version.                  - %
+% - The latest version of this license is in                                - %
+% -   http://www.latex-project.org/lppl.txt                                 - %
+% - and version 1.3 or later is part of all distributions of LaTeX          - %
+% - version 2005/12/01 or later.                                            - %
+% -                                                                         - %
+% - This work has the LPPL maintenance status `maintained'.                 - %
+% -                                                                         - %
+% - The Current Maintainer of this work is Clemens Niederberger.            - %
+% -                                                                         - %
+% - This work consists of the files modiagram.sty, modiagram_doc_de.tex,    - %
+% - modiagram_doc_de.tex, README                                            - %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\documentclass{scrartcl}
+\usepackage[ngerman]{babel}
+\usepackage[utf8]{inputenx}
+\usepackage[dvipsnames]{xcolor}
+  \colorlet{code}{RawSienna}
+\usepackage{modiagram,xspace,siunitx,framed,chemfig}
+\usepackage{showexpl}
+\usepackage[version=3]{mhchem}
+
+\usepackage{showexpl}
+\lstset{
+  language         = [LaTeX]TeX,
+  basicstyle       = {\ttfamily\small\color{code!80}},
+  breaklines       = true,
+  commentstyle     = {\color[named]{Gray}},
+  backgroundcolor  = \color{yellow!20},
+  numbers          = left,
+  numberstyle      = \tiny,
+  numberblanklines = true,
+  numbersep        = .3em,
+  xleftmargin      = 1em,
+  gobble           = 1
+}
+
+\usepackage{hyperref}
+\hypersetup
+  {
+    colorlinks         = true,
+    urlcolor           = blue!80,
+    linkcolor          = blue!80,
+    plainpages         = false,
+    bookmarksopen      = true,
+    bookmarksopenlevel = 2,
+    bookmarksnumbered  = true,
+    pdfauthor          = {Clemens Niederberger},
+    pdftitle           = {MOdiagram - Manual},
+    pdfsubject         = {Create MO diagrams with LaTeX},
+    pdfkeywords        = {MOdiagram},
+    pdfcreator         = {LaTeX}
+  }
+
+\newcommand*\MOname{\textsf{MOdiagram}\xspace}
+\newcommand*\MOversion{0.1\xspace}
+\newcommand*\MOdate{2011/09/25}
+
+\newcommand*\paket[1]{\textsf{#1}\footnote{\url{http://www.ctan.org/pkg/#1}}}
+
+\newcommand*\changefont[3]{\fontfamily{#1}\fontseries{#2}\fontshape{#3}\selectfont}
+
+\DeclareDocumentEnvironment{myquote}{o}
+  {\quote\small\changefont{cmss}{m}{sl}}
+  {\IfNoValueF{#1}{\par\noindent\parbox{\linewidth}{\raggedleft\normalfont\itshape#1}}\endquote}
+\NewDocumentCommand\cmd{v}{{\color{code!80}\ttfamily#1}}
+
+\newcommand*\TikZ{\mbox{Ti\textbf{\textit{k}}Z}\xspace}
+\newcommand*\bzw{\mbox{bzw.}\xspace}
+
+\begin{document}
+
+\begin{titlepage}
+ \centering
+ \Huge MOdiagram v\MOversion
+ \vskip.5cm
+ \Large\MOdate
+ \vskip.5cm
+ \large Clemens \textsc{Niederberger}
+ \vskip.25cm
+ \normalsize\url{http://www.mychemistry.eu/}\\
+ \href{mailto:contact@mychemistry.eu}{contact@mychemistry.eu}
+ \vskip2cm
+ \begin{abstract}
+  \MOname stellt eine Umgebung und Befehle zur Verfügung, um Molekülorbital-Diagramme zu erstellen.
+ \end{abstract}
+ \begin{MOdiagram}[style=fancy,distance=7cm,AO-width=15pt,labels,names]
+  \atom[N]{left}{
+    2p = {0;up,up,up}
+  }
+  \atom[O]{right}{
+    2p = {2;pair,up,up}
+  }
+  \molecule[NO]{
+    2pMO = {1.8,.4;pair,pair,pair,up,,},
+    color = { 2piy*=red }
+  }
+ \end{MOdiagram}
+\end{titlepage}
+
+\tableofcontents
+
+\section{Lizenz, Voraussetzungen}
+\MOname v\MOversion steht unter der \LaTeX\ Project Public License Version 1.3 oder später.\newline(\url{http://www.latex-project.org/lppl.txt})
+
+\MOname benötigt die Pakete \paket{expl3}, \paket{xparse}, \paket{l3keys2e}, \textsf{tikz}\footnote{\url{http://www.ctan.org/pkg/pgf}}, \paket{amsmath} und \paket{textgreek}. Außerdem werden die \TikZ-Libraries \textsf{calc} und \textsf{arrows} geladen.
+
+Kenntnisse des \textsf{pgf}- \bzw des \textsf{tikz}-Paketes sind von Vorteil.
+
+\section{Motivation}
+Dieses Paket ist enstanden wegen einer Frage auf \url{http://tex.stackexchange.com/}, genauer gesagt wegen der Frage \href{http://tex.stackexchange.com/questions/13863/molecular-orbital-diagrams-in-latex}{Molecular orbital diagrams in LaTeX}. Dort heißt es
+\begin{myquote}
+ I'm wondering if anyone has seen a package for drawing (qualitative) molecular orbital splitting diagrams in \LaTeX? Or if there exist any packages that can be easily re-purposed to this task?
+
+ Otherwise, I think I'll have a go at it in \TikZ.
+\end{myquote}
+Dort wird das Problem mit \TikZ gelöst, da es bis dato noch kein Paket für diese Aufgabe gab. \MOname soll diese Lücke nun füllen.
+
+\section{Basisbefehle}
+Alle MO-Diagramme werden mit der Umgebung \cmd=MOdiagram= erzeugt. Innerhalb dieser Umgebung sind zunächst zwei Befehle wichtig.
+
+\subsection{Der \texttt{\textbackslash atom} Befehl}
+\begin{framed}
+ \cmd=\atom[<name>]{<pos>}{<AO-spec>}=
+ \begin{itemize}\small
+  \item\cmd=<name>= (o) Beschriftung des Atoms
+  \item\cmd=<pos>= (m) links oder rechts im MO-Diagramm
+  \item\cmd=<AO-spec>= (m) Spezifizierung der Atom-Orbitale (AO)
+ \end{itemize}
+\end{framed}
+Sehen wir uns den Befehl einmal an:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{right}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+Wie Sie sehen können, ist die Angabe von \cmd=<AO-spec>= wesentlich für die Ausgabe der Orbital-Niveaus und den enthaltenen Elektronen. Folgende Schüssel-Wert-Paare können durch Kommata getrennt eingegeben werden:
+\begin{framed}
+ \begin{itemize}
+  \item\cmd+1s={<rel. energy>; <el-spec>}+
+  \item\cmd+2s={<rel. energy>; <el-spec>}+
+  \item\cmd+2p={<rel. energy>; <x el-spec>, <y el-spec>, <z el-spec>}+
+ \end{itemize}
+\end{framed}
+Die \cmd=<el-spec>= können die Werte \cmd=pair=, \cmd=up= und \cmd=down= annehmen oder leer gelassen werden. \cmd=<rel. energy>= ist in etwa mit der $y$-Koordinate gleichzusetzen und verschiebt das AO in vertikaler Richtung um \cmd=<rel. energy>= \si{\centi\metre} auf- (positiv) oder abwärts (negativ).
+
+Das Argument \cmd=<pos>= wird wichtig, wenn die p-Orbitale verwendet werden. Vergleichen Sie folgendes Beispiel mit dem vorhergehenden:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+Verwendet man beide Varianten auf einmal, so sieht man außerdem, dass das rechte Atom gegenüber dem linken nach rechts verschoben ist. Der Betrag, um den das rechte verschoben ist, beträgt per Default \SI{4}{\centi\metre} und kann individuell angepasst werden (siehe Seite \pageref{option:distance}).
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+  \atom{right}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+Der Sinn der Verschiebung wird klar, wenn wir den nächsten Befehl dazu nehmen.
+
+\subsection{Der \texttt{\textbackslash molecule} Befehl}
+\begin{framed}
+ \cmd=\molecule[<name>]{<MO-spec>}=
+ \begin{itemize}\small
+  \item\cmd=<name>= (o) Beschriftung des Moleküls
+  \item\cmd=<MO-spec>= (m) Spezifizierung der Molekül-Orbitale (MO)
+ \end{itemize}
+\end{framed}
+Zunächst einmal ein Beispiel:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {  0; up} }
+  \atom{right}{ 1s = {  0; up} }
+  \molecule { 1sMO = {.75; pair, } }
+ \end{MOdiagram}
+\end{LTXexample}
+Durch den Befehl \cmd=\molecule= werden die Atom-Orbitale (AO) verbunden und die entsprechenden bindenden und antibindenden Orbitale des Moleküls (MO) gezeichnet. \cmd=\molecule= kann nur verwendet werden, \emph{nachdem} man bereits \emph{beide} Atome gesetzt hat, da die zu verbindenden Orbitale bekannt sein müssen.
+
+Das Argument \cmd=<MO-spec>= erwartet dabei durch Kommata getrennt folgende Key-Value-Paare:
+\begin{framed}
+ \begin{itemize}
+  \item\cmd+1sMO={<energy gain>; <s el-spec>, <s* el-spec>}+ (verbindet die durch \cmd=1s= spezifizierten AO.)
+  \item\cmd+2sMO={<energy gain>; <s el-spec>, <s* el-spec>}+ (verbindet die durch \cmd=2s= spezifizierten AO.)
+  \item\cmd+2pMO={<s energy gain>, <p energy gain>; <s el-spec>, <py el-spec>, <pz el- spec>, <py* el-spec>, <pz* el-spec>, <s* el-spec>}+ (verbindet die durch \cmd=2p= spezifizierten AO.)
+ \end{itemize}
+\end{framed}
+Es ist dabei zu beachten, dass die entsprechenden AO gesetzt sein müssen, um sie verbinden zu können. Folgendes wird nicht funktionieren:
+\begin{lstlisting}
+ \begin{MOdiagram} 
+  \atom{left} { 1s = {  0; } }
+  \atom{right}{ 1s = {  0; } }
+  \molecule { 2sMO = {.75; , } }
+ \end{MOdiagram}
+\end{lstlisting}
+Der Wert, der für \cmd=<energy gain>= angegeben wird, gibt an, wieviele \si{\centi\metre} das bindende MO unter dem niedrigeren AO \bzw wieviel das antibindende MO über dem höheren AO gesetzt wird.
+
+\begin{LTXexample}[pos=b]
+ Gleiche Level:
+ \begin{MOdiagram}
+  \atom{left} { 1s = {  0; up} }
+  \atom{right}{ 1s = {  0; up} }
+  \molecule { 1sMO = {.75; pair, } }
+ \end{MOdiagram}
+
+ Unterschiedliche Level:
+ \begin{MOdiagram}
+  \atom{left} { 1s = {  0; up} }
+  \atom{right}{ 1s = {  1; up} }
+  \molecule { 1sMO = {.25; pair, } }
+ \end{MOdiagram}
+\end{LTXexample}
+Beachten Sie, dass Sie bei \cmd=2pMO= \emph{zwei} solche Werte angeben müssen: die Aufspaltung der \textsigma-Orbitale und die Aufspaltung der \textpi-Orbitale.
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 2p = { 0; up, up , } }
+  \atom{right}{ 2p = { 1; up, up , } }
+  \molecule { 2pMO = { 1.5, .75; pair, up, up , , , } } 
+ \end{MOdiagram}
+\end{LTXexample}
+
+Das komplette MO-Diagramm für Triplett-Disauerstoff könnte nun etwa folgendermaßen aussehen:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left}{
+    1s = {0;pair},
+    2s = {2;pair},
+    2p = {5;pair,up,up}
+  }
+  \atom{right}{
+    1s = {0;pair},
+    2s = {2;pair},
+    2p = {5;pair,up,up}
+  }
+  \molecule{
+    1sMO  = {.5;pair,pair},
+    2sMO  = {.5;pair,pair},
+    2pMO  = {1.5,.5;pair,pair,pair,up,up,}
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsection{Die Namensgebung}\label{Namensgebung}
+Da man üblicherweise die AO und MO auch beschriften (können) möchte und sie in der \cmd=MOdiagram=-Umgebung \TikZ-Nodes entsprechen, ist die interne Benennung wichtig. Diese folgt eng der tatsächlichen Funktion:
+\begin{center}
+\begin{MOdiagram}[distance=6cm,AO-width=20pt,labels-fs=\tt\footnotesize]
+ \atom{left}{
+   1s={0;},
+   2s={2;},
+   2p={5;,,},
+   label={ 1sleft={1sleft}, 2sleft={2sleft}, 2pxleft={2pxleft}, 2pyleft={2pyleft}, 2pzleft={2pzleft} }
+ }
+ \atom{right}{
+   1s={0;},
+   2s={2;},
+   2p={5;,,},
+   label={ 1sright={1sright}, 2sright={2sright}, 2pxright={2pxright}, 2pyright={2pyright}, 2pzright={2pzright} }
+ }
+ \molecule{
+   1sMO={.5;,},
+   2sMO={.5;,},
+   2pMO={1.5,.5;,,,,,},
+   label={ 1sigma={1sigma}, 1sigma*={1sigma*}, 2sigma={2sigma}, 2sigma*={2sigma*}, 2psigma={2psigma}, 2psigma*={2psigma*}, 2piy={2piy}, 2piy*={2piy*}, 2piz={2piz}, 2piz*={2piz*} }
+ }
+\end{MOdiagram}
+\end{center}
+Mit diesen Bezeichnungen ist es möglich, sie mit den üblich \TikZ-Befehlen zu referenzieren:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0; } }
+  \atom{right}{ 1s = {0; } }
+  \molecule { 1sMO = {.75; , } }
+  \draw[<->,red,semithick] (1sigma) -- (1sigma*) ;
+  \draw[red] (1sigma*) ++ (2cm,.5cm) node {Aufspaltung} ;
+ \end{MOdiagram}
+\end{LTXexample}
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0; } }
+  \atom{right}{ 1s = {0; } }
+  \molecule { 1sMO = {.75; , } }
+  \draw[draw=blue,fill=blue!20,opacity=.5] (1sigma*) circle (8pt);
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsection{AOs und MOs irgendwo}
+Nicht immer reichen die Standardorbitale aus, um ein sinnvolles MO-Diagramm zu zeichen. Beispielsweise würde man im MO-Diagramm von \ce{XeF2} wohl folgenden Ausschnitt für die 3Z/2E-Bindung benötigen, der die Wechselwirkung eines Xe-p-Orbitals mit der antibindenden Kombination zweier F-p-Orbitale zeigt:
+\begin{center}
+ \begin{MOdiagram}[names]
+ \atom[\lewis{0.,F}\hspace*{5mm}\lewis{4.,F}]{left}{}
+ \atom[Xe]{right}{}
+ \molecule[\ce{XeF2}]{}
+ \AO[a](1cm){s}{0;up}
+ \AO[b](1cm){s}{.25;up}
+ \AO[c](3cm){s}{-1;pair}
+ \AO[d](3cm){s}{0;pair}
+ \AO[e](3cm){s}{1.5;}
+ \AO[f](5cm){s}{1.25;pair}
+ \connect{ a & d , b & c , b & e , c & f , e & f }
+ \node[right,xshift=4mm] at (c) {\footnotesize bindend};
+ \node[above] at (d.90) {\footnotesize nicht bindend};
+ \node[above] at (e.90) {\footnotesize antibindend};
+\end{MOdiagram}
+\end{center}
+Um solche MO-Diagramme erstellen zu können, gibt es folgenden Befehl:
+\begin{framed}
+ \cmd=\AO[<name>](<xshift>){<type>}{<energy>;<el-spec>}=
+ \begin{itemize}\small
+  \item\cmd=<name>= (o) Name der Node
+  \item\cmd=<xshift>= (o) Vertikale Position des Orbitals, eine \TeX-Länge mit Einheit
+  \item\cmd=<type>= (m) \cmd=s= oder \cmd=p=
+  \item\cmd=<AO-spec>= (m) Spezifizierung des Atom-Orbitals 
+ \end{itemize}
+\end{framed}
+Je nach \cmd=<type>= werden damit ein s- oder drei p-Orbitale erzeugt.
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \AO{s}{0;}
+  \AO(-20pt){p}{1;pair,up,down}
+ \end{MOdiagram}
+\end{LTXexample}
+Beachten Sie, dass als \cmd=<el-spec>= beim Typ \cmd=s= nur eine Spezifikation erwartet wird, beim Typ \cmd=p= aber drei durch Komma getrennte.
+
+Möchte man ein AO genau an die Position eines Atoms setzen, so muss man deren \cmd=<xshift>= kennen. Die haben per Default folgende Werte (siehe auch Abschnitt \ref{orbital-positionen}):\label{xshift}
+\begin{itemize}
+ \item atom left: \SI{1}{\centi\metre}
+ \item molecule: \SI{3}{\centi\metre}
+ \item atom right: \SI{5}{\centi\metre}
+\end{itemize}
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} {1s={0;}}
+  \atom{right}{1s={0;}}
+  \molecule {1sMO={1;,}}
+  \AO(1cm){s}{2;pair}
+  \AO(3cm){s}{2;pair}
+  \AO(5cm){s}{2;pair}
+ \end{MOdiagram}
+\end{LTXexample}
+In p-Orbitalen findet pro Orbital per Default eine Verschiebung um \SI{20}{pt} statt, was einer zweifachen Verschiebung um die noch zu besprechende Länge \cmd=AO-width= (siehe Abschnitt \ref{option:AO-width}) entspricht:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} {2p={0;,,}}
+  \atom{right}{2p={0;,,}}
+  % ueber dem linken:
+  \AO(1cm)     {s}{ .5;pair}
+  \AO(1cm-20pt){s}{  1;up}
+  \AO(1cm-40pt){s}{1,5;down}
+  % ueber dem rechten:
+  \AO(5cm)     {s}{ .5;pair}
+  \AO(5cm+20pt){s}{  1;up}
+  \AO(5cm+40pt){s}{1.5;down}
+ \end{MOdiagram}
+\end{LTXexample}
+
+Auch die mit \cmd=\AO= gesetzten Orbitale können mit Linien verbunden werden. Das kann man natürlich mit dem \cmd=\draw=-Befehl machen:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \AO[a]{s}{0;} \AO[b](2cm){s}{1;}
+  \AO[c]{s}{2;} \AO[d](2cm){s}{1.5;}
+  \draw (a) -- (b) (c) -- (d);
+ \end{MOdiagram}
+\end{LTXexample}
+Soll die Verbindungslinie aber zu dem Stil der durch \cmd=\molecule= erzeugten Linien\footnote{Dieser Stil kann angepasst werden, siehe Seite \pageref{option:lines}.} passen, dann sollte man den Befehl \cmd=\connect= verwenden.
+\begin{framed}
+ \cmd=\connect{<AO-connect>}=
+ \begin{itemize}\small
+  \item\cmd=<AO-connect>= (m) durch Kommata getrennte Liste von durch \cmd=&= verbundenen Node-Paaren, die verbunden werden sollen.
+ \end{itemize}
+\end{framed}
+Dieser Befehl erwartet eine durch Kommata getrennte Liste von durch \cmd=&= verbundenen Paaren von Node-Namen derer Nodes, die verbunden werden sollen:
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \AO[a]{s}{0;} \AO[b](2cm){s}{1;}
+  \AO[c]{s}{2;} \AO[d](2cm){s}{1.5;}
+  \connect{ a & b, c & d }
+ \end{MOdiagram}
+\end{LTXexample}
+Einige Punkte müssen dabei noch erwähnt werden: \cmd=\connect= fügt der ersten Node den Anker \cmd=east= und der zweiten den Anker \cmd=west= hinzu. Damit funktioniert eine vernünftige Verbindung nur von links nach rechts. Allerdings können nach dem üblichen \TikZ-Schema auch eigene Anker gesetzt werden:
+\begin{LTXexample}
+ \begin{tikzpicture}
+  \draw (0,0) node (a) {a} ++ (1,0) node (b) {b}
+        ++ (0,1) node (c) {c} ++ (-1,0) node (d) {d} ;
+  \connect{ a.90 & d.-90, c.180 & d.0 }
+ \end{tikzpicture}
+\end{LTXexample}
+
+\subsection{Die Positionen}\label{orbital-positionen}
+In folgender Darstellung sehen Sie die Werte, die die $x$-Positionen der Orbitale annehmen in Abhängigkeit von \cmd=<distance>= (\cmd=<dist>=) und \cmd=<AO-width>= (\cmd=<AO>=). Diese Längen und wie man sie ändert werden in den Abschnitten \ref{option:distance} und \ref{option:AO-width} besprochen.
+\begin{center}
+\begin{MOdiagram}[distance=6cm,AO-width=25pt,labels-fs=\tt\footnotesize,labels-style={text width=40pt,align=center}]
+ \atom{left}{
+   1s={0;},
+   2s={3;},
+   2p={8;,,},
+   label={ 1sleft={1cm}, 2sleft={1cm}, 2pxleft={1cm}, 2pyleft={1cm - 2*<AO>}, 2pzleft={1cm - 4*<AO>} } }
+ \atom{right}{
+   1s={0;},
+   2s={3;},
+   2p={8;,,},
+   label={ 1sright={1cm + <dist>}, 2sright={1cm + <dist>}, 2pxright={1cm+ <dist>}, 2pyright={1cm + <dist> + 2*<AO>}, 2pzright={1cm + <dist> + 4*<AO>} } }
+ \molecule{
+   1sMO={.75;,},
+   2sMO={.75;,},
+   2pMO={3,1;,,,,,},
+   label={ 1sigma={.5*<dist> + 1cm}, 1sigma*={.5*<dist> + 1cm}, 2sigma={.5*<dist> + 1cm}, 2sigma*={.5*<dist> + 1cm}, 2psigma={.5*<dist> + 1cm}, 2psigma*={.5*<dist> + 1cm}, 2piy={.5*<dist> + 1cm - <AO>}, 2piy*={.5*<dist> + 1cm - <AO>}, 2piz={.5*<dist> + 1cm + <AO>}, 2piz*={.5*<dist> + 1cm + <AO>} }
+ }
+\end{MOdiagram}
+\end{center}
+
+\section{Anpassen des Layouts}
+\subsection{Umgebungs-Optionen}
+Es gibt folgende Optionen, mit denen das Aussehen der MO-Diagramme verändert werden kann.
+\begin{itemize}
+ \item\cmd+style=<type>+ Verändern des Stils der Orbitale und Verbindungslinien, Abschnitt \ref{option:style}.
+ \item\cmd+distance=<dim>+ Der Abstand zwischen linkem und rechtem Atom, Abschnitt \ref{option:distance}.
+ \item\cmd+AO-width=<dim>+ Die Größe der Orbitale ändern, Abschnitt \ref{option:AO-width}.
+ \item\cmd+lines=<tikz>+ \TikZ-Stil der Verbindungslinien anpassen, Abschnitt \ref{option:lines}.
+ \item\cmd+names=<bool>+ Atome und Molekül beschriften, Abschnitt \ref{option:names}.
+ \item\cmd+labels=<bool>+ Orbitale mit Default Beschriftung versehen, Abschnitt \ref{option:labels}.
+ \item\cmd+labels-fs=<cs>+ Schriftgröße der Label-Beschriftung verändern, Abschnitt \ref{option:labels-fs}.
+ \item\cmd+labels-style=<tikz>+ \TikZ-Stil der Label-Beschriftung verändern, Abschnitt \ref{option:labels-style}.
+\end{itemize}
+Sie alle werden nachfolgend besprochen. Aufgerufen werden sie entweder als Option der Umgebung
+\begin{lstlisting}
+ \begin{MOdiagram}[<key = value>]
+  ...
+ \end{MOdiagram}
+\end{lstlisting}
+oder über den Setup-Befehl
+\begin{framed}
+ \cmd+\MOsetup{<key = value>}+
+ \begin{itemize}\small
+  \item\cmd+<key = val>+ (m) komma-separierte Schlüssel-Wert-Liste
+ \end{itemize}
+\end{framed}
+
+\subsubsection{Option \texttt{style}}\label{option:style}
+Es gibt vier verschiedene Stile, aus denen ausgewählt werden kann:
+\begin{itemize}
+ \item\cmd+style=plain+ \AOinline[style=plain]{pair} (Default)
+ \item\cmd+style=square+ \AOinline[style=square]{pair}
+ \item\cmd+style=round+ \AOinline[style=round]{pair}
+ \item\cmd+style=fancy+ \AOinline[style=fancy]{pair}
+\end{itemize}
+Sehen wir uns das MO-Diagramm für \ce{H2} in den verschiedenen Stilen an:
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=plain]% Default
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=square]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=round]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=fancy]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsubsection{Option \texttt{distance}}\label{option:distance}
+Je nach Label und Beschriftungen können die \SI{4}{\centi\metre}, durch die das linke und das rechte Atom getrennt sind, zu wenig sein. Mit der Option \cmd+distance=<dim>+ lässt sie sich verändern. Damit wird die Position des rechten Atoms auf \cmd=1cm + <dim>= gesetzt und die Position des Moleküls auf \cmd=0.5*(1cm + <dim>)=, siehe auch Seite \pageref{xshift} und Abschnitt \ref{orbital-positionen}.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[distance=6cm]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsubsection{Option \texttt{AO-width}}\label{option:AO-width}
+Die Länge \cmd=AO-width= enstpricht der Länge des waagerechten Strichs eines Orbitals im \cmd=plain=-Stil und beträgt per Default \SI{10}{pt}.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[AO-width=15pt]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=fancy,AO-width=15pt]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+Durch das Verändern von \cmd=AO-width= ändern sich auch die Positionen der p- und \textpi-Orbitale, siehe Abschnitt \ref{orbital-positionen}.
+
+\subsubsection{Option \texttt{lines}}\label{option:lines}
+Der Option \cmd=lines= können \TikZ-Keys angegeben werden, um den Stil der Verbindungslinien zu ändern.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[lines={gray,thin}]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsubsection{Option \texttt{names}}\label{option:names}
+Verwendet man die Option \cmd=names=, werden den Atomen und dem Molekül Beschriftungen hinzugefügt, sofern man die optionalen Argumente von \cmd=\atom= und/oder \cmd=\molecule= verwendet hat.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[names]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsubsection{Option \texttt{labels}}\label{option:labels}
+Mit der Option \cmd=labels= werden vordefinierte Labels an die Orbitale geschrieben. Diese Labels können auch geändert werden, siehe Abschnitt \ref{key:label}.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsubsection{Option \texttt{labels-fs}}\label{option:labels-fs}
+Per Default werden die Labels mit der Schriftgröße \cmd=\small= gesetzt. Wenn man das ändern möchte, kann man die Option \cmd=labels-fs= verwenden.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels,labels-fs=\footnotesize]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+Damit ist es auch möglich, den Schriftstil zu verändern.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels,labels-fs=\sffamily\footnotesize]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsubsection{Option \texttt{labels-style}}\label{option:labels-style}
+Mit der Option \cmd=labels-style= kann man den \TikZ-Stil der Nodes ändern, in die die Labels geschrieben werden.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels,labels-style={blue}]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsection{\texttt{\textbackslash atom} und \texttt{\textbackslash molecule} spezifische Anpassungen}
+\subsubsection{Der \texttt{label} Key}\label{key:label}
+Wenn man die vordefinierten Label nicht verwenden möchte, also eigene Label ändern möchte oder auch nur einzelne Label verwenden möchte, kann man den Key \cmd=label= einsetzen. Dieser Key wird im \cmd=\atom=- und im \cmd=\molecule=-Befehl bei \cmd=<AO-spec>= \bzw \cmd=<MO-spec>= eingesetzt. Der Key erwartet eine durch Kommata getrennte Schlüssel-Wert-Liste. Als Schlüssel werden die in Abschnitt \ref{Namensgebung} vorgestellten Namen verwendet, mit denen das zu beschriftende Orbital spezifiziert wird.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels-fs=\footnotesize]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{
+    1sMO  = {.75;pair,},
+    label = { 1sigma = {bindendes MO} }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ \begin{MOdiagram}[style=square,distance=6cm]
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{
+    1sMO  = {.75;pair,} ,
+    label = {
+      1sigma  = $\sigma$,
+      1sigma* = $\sigma^*$
+    }
+  }
+  \node[right] at (1sigma.-45) {bindend};
+  \node[right] at (1sigma*.45) {antibindend};
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsubsection{Der \texttt{color} Key}\label{key:color}
+Analog zum \cmd=label=-Key kann der \cmd=color=-Key verwendet werden, um die Elektronen eines Orbitals farbig darzustellen.
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels-fs=\footnotesize]
+  \atom[H]{left}{
+    1s = {0;pair},
+    color = { 1sleft = blue }
+  }
+  \atom[H]{right}{
+    1s = {0;pair},
+    color = { 1sright = red }
+  }
+  \molecule[\ce{H2}]{
+    1sMO  = {.75;pair,pair},
+    label = { 1sigma = {bindendes MO} },
+    color = { 1sigma = green, 1sigma* = cyan }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsection{Energie-Achse}
+Zuletzt möchte man unter Umständen gerne eine Energie-Achse an das Diagramm zeichnen. Dafür gibt es den Befehl \cmd=\EnergyAxis=
+\begin{framed}
+ \cmd+\EnergyAxis[<key = val>]+
+ \begin{itemize}\small
+  \item\cmd+<key = val>+ (o) Schlüssel-Wert-Paare, um die Achse zu modifizieren.
+ \end{itemize}
+\end{framed}
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{ 1sMO = {.75;pair,} }
+  \EnergyAxis
+ \end{MOdiagram}
+\end{LTXexample}
+Es gibt derzeit zwei Keys, mit denen die Achse modifiziert werden kann.
+\begin{framed}
+ \begin{itemize}
+  \item\cmd+title=<title>+ Achsenbeschriftung (Default: \cmd=energy=).
+  \item\cmd+head=<tikz-arrow-head>+ Pfeilspitze; hier können die Pfeilspitzen verwendet werden, die in der \TikZ-Library \textsf{arrows} spezifiziert sind (pgf-Manual v2.10 Seiten 256ff.) (Default: \cmd=>=).
+ \end{itemize}
+\end{framed}
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{ 1sMO = {.75;pair,} }
+  \EnergyAxis[title]
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{ 1sMO = {.75;pair,} }
+  \EnergyAxis[title=Energie,head=stealth]
+ \end{MOdiagram}
+\end{LTXexample}
+
+\subsection{Beispiele}
+\begin{LTXexample}[pos=b]
+ % use packages 'mhchem' (and 'textgreek' loaded by 'MOdiagram')
+ \begin{figure}
+  \centering
+  \begin{MOdiagram}[style=square,labels,names,AO-width=8pt,labels-fs=\footnotesize]
+   \atom[\ce{O_a}]{left}{
+     1s = {0;pair},
+     2s = {2;pair},
+     2p = {5;pair,up,up}
+   }
+   \atom[\ce{O_b}]{right}{
+     1s = {0;pair},
+     2s = {2;pair},
+     2p = {5;pair,up,up}
+   }
+   \molecule[\ce{O2}]{
+     1sMO  = {.5;pair,pair},
+     2sMO  = {.5;pair,pair},
+     2pMO  = {1.5,.5;pair,pair,pair,up,up,},
+     color = { 2piy*=red, 2piz*=red }
+   }
+   \EnergyAxis
+  \end{MOdiagram}
+  \caption{MO-Diagramm von $^3$\textSigma-\ce{O2}.}
+ \end{figure}
+\end{LTXexample}
+\begin{LTXexample}[pos=b]
+ % use package 'chemfig'
+ \begin{figure}
+  \centering
+  \begin{MOdiagram}[style=fancy,distance=7cm,AO-width=15pt,labels]
+   \atom[N]{left}{
+     2p = {0;up,up,up}
+   }
+   \atom[O]{right}{
+     2p = {2;pair,up,up}
+   }
+   \molecule[NO]{
+     2pMO = {1.8,.4;pair,pair,pair,up,,},
+     color = { 2piy*=red }
+   }
+   \EnergyAxis[title]
+  \end{MOdiagram}
+  \caption{Ausschnitt aus dem MO-Diagramm von \protect\Lewis{4.,NO}.}
+ \end{figure}
+\end{LTXexample}
+
+\end{document}
\ No newline at end of file
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@@ -0,0 +1,806 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% --------------------------------------------------------------------------- %
+% - MOdiagram - modiagram_doc_en.tex                                        - %
+% - easy creation of molecular orbital diagrams                             - %
+% --------------------------------------------------------------------------- %
+% - Clemens NIEDERBERGER                                                    - %
+% - 2011/09/25                                                              - %
+% --------------------------------------------------------------------------- %
+% - http://www.mychemistry.eu/                                              - %
+% - contact@mychemistry.eu                                                  - %
+% --------------------------------------------------------------------------- %
+% - If you have any ideas, questions, suggestions or bugs to report, please - %
+% - feel free to contact me.                                                - %
+% --------------------------------------------------------------------------- %
+% - Copyright 2011 Clemens Niederberger                                     - %
+% -                                                                         - %
+% - This work may be distributed and/or modified under the                  - %
+% - conditions of the LaTeX Project Public License, either version 1.3      - %
+% - of this license or (at your option) any later version.                  - %
+% - The latest version of this license is in                                - %
+% -   http://www.latex-project.org/lppl.txt                                 - %
+% - and version 1.3 or later is part of all distributions of LaTeX          - %
+% - version 2005/12/01 or later.                                            - %
+% -                                                                         - %
+% - This work has the LPPL maintenance status `maintained'.                 - %
+% -                                                                         - %
+% - The Current Maintainer of this work is Clemens Niederberger.            - %
+% -                                                                         - %
+% - This work consists of the files modiagram.sty, modiagram_doc_de.tex,    - %
+% - modiagram_doc_de.tex, README                                            - %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\documentclass{scrartcl}
+\usepackage{xparse}[2011/09/05]
+\usepackage[english]{babel}
+\usepackage[utf8]{inputenx}
+\usepackage[dvipsnames]{xcolor}
+  \colorlet{code}{RawSienna}
+\usepackage{modiagram,xspace,siunitx,framed,chemfig}
+\usepackage{showexpl}
+\usepackage[version=3]{mhchem}
+
+\usepackage{showexpl}
+\lstset{
+  language         = [LaTeX]TeX,
+  basicstyle       = {\ttfamily\small\color{code!80}},
+  breaklines       = true,
+  commentstyle     = {\color[named]{Gray}},
+  backgroundcolor  = \color{yellow!20},
+  numbers          = left,
+  numberstyle      = \tiny,
+  numberblanklines = true,
+  numbersep        = .3em,
+  xleftmargin      = 1em,
+  gobble           = 1
+}
+
+\usepackage{hyperref}
+\hypersetup
+  {
+    colorlinks         = true,
+    urlcolor           = blue!80,
+    linkcolor          = blue!80,
+    plainpages         = false,
+    bookmarksopen      = true,
+    bookmarksopenlevel = 2,
+    bookmarksnumbered  = true,
+    pdfauthor          = {Clemens Niederberger},
+    pdftitle           = {MOdiagram - Manual},
+    pdfsubject         = {Create MO diagrams with LaTeX},
+    pdfkeywords        = {MOdiagram},
+    pdfcreator         = {LaTeX}
+  }
+
+\newcommand*\MOname{\textsf{MOdiagram}\xspace}
+\newcommand*\MOversion{0.1\xspace}
+\newcommand*\MOdate{2011/09/25}
+
+\newcommand*\paket[1]{\textsf{#1}\footnote{\url{http://www.ctan.org/pkg/#1/}}}
+% \newcommand*\paket[1]{\textsf{#1}}
+
+\newcommand*\changefont[3]{\fontfamily{#1}\fontseries{#2}\fontshape{#3}\selectfont}
+
+\DeclareDocumentEnvironment{myquote}{o}
+  {\quote\small\changefont{cmss}{m}{sl}}
+  {\IfNoValueF{#1}{\par\noindent\parbox{\linewidth}{\raggedleft\normalfont\itshape#1}}\endquote}
+\NewDocumentCommand\cmd{v}{{\color{code!80}\ttfamily#1}}
+
+\newcommand*\TikZ{\mbox{Ti\textbf{\textit{k}}Z}\xspace}
+\newcommand*\bzw{\mbox{bzw.}\xspace}
+
+\begin{document}
+
+\begin{titlepage}
+ \centering
+ \Huge MOdiagram v\MOversion
+ \vskip.5cm
+ \Large\MOdate
+ \vskip.5cm
+ \large Clemens \textsc{Niederberger}
+ \vskip.25cm
+ \normalsize\url{http://www.mychemistry.eu/}\\
+ \href{mailto:contact@mychemistry.eu}{contact@mychemistry.eu}
+ \vskip2cm
+ \begin{abstract}
+  \MOname provides an environment and commands for the creation of molecular orbital diagrams.
+ \end{abstract}
+ \begin{MOdiagram}[style=fancy,distance=7cm,AO-width=15pt,labels,names]
+  \atom[N]{left}{
+    2p = {0;up,up,up}
+  }
+  \atom[O]{right}{
+    2p = {2;pair,up,up}
+  }
+  \molecule[NO]{
+    2pMO = {1.8,.4;pair,pair,pair,up,,},
+    color = { 2piy*=red }
+  }
+ \end{MOdiagram}
+\end{titlepage}
+
+\tableofcontents
+
+\section{Licence, Requirements}
+\MOname v\MOversion underlies the \LaTeX\ Project Public License version 1.3 or later.\newline(\url{http://www.latex-project.org/lppl.txt})
+
+\MOname needs the packages \paket{expl3}, \paket{xparse}, \paket{l3keys2e}, \textsf{tikz}\footnote{\url{http://www.ctan.org/pkg/pgf/}}, \paket{amsmath} and \paket{textgreek}. Additionally the \TikZ libraries \textsf{calc} and \textsf{arrows} are loaded.
+
+It is useful to be familiar with the \paket{pgf} or the \paket{tikz} package.
+
+\section{Motivation}
+This package has been written as a reaction to a question on \url{http://tex.stackexchange.com/}. To be more precise: as a rection to the question \href{http://tex.stackexchange.com/questions/13863/molecular-orbital-diagrams-in-latex}{Molecular orbital diagrams in LaTeX}. There it says
+\begin{myquote}
+ I'm wondering if anyone has seen a package for drawing (qualitative) molecular orbital splitting diagrams in \LaTeX? Or if there exist any packages that can be easily re-purposed to this task?
+
+ Otherwise, I think I'll have a go at it in \TikZ.
+\end{myquote}
+The problem was solved using \TikZ, since no package existed for that purpose. \MOname is intended to fill this gap.
+
+\section{Main Commands}
+Every molecular orbital (MO) diagrams are created using the environment \cmd=MOdiagram= . Inside this environment two commands are important to begin with.
+
+\subsection{The \texttt{\textbackslash atom} Command}
+\begin{framed}
+ \cmd=\atom[<name>]{<pos>}{<AO-spec>}=
+ \begin{itemize}\small
+  \item\cmd=<name>= (o) caption of the atom
+  \item\cmd=<pos>= (m) on the left or the right in the diagram
+  \item\cmd=<AO-spec>= (m) specifications of the atomic orbitals (AO)
+ \end{itemize}
+\end{framed}
+Let's take a look at an example:
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{right}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+As you can see, the argument \cmd=<AO-spec>= is essential to create the actual orbitals and the electrons within. You can use these key/value pairs to specify what you need:
+\begin{framed}
+ \begin{itemize}
+  \item\cmd+1s={<rel. energy>; <el-spec>}+
+  \item\cmd+2s={<rel. energy>; <el-spec>}+
+  \item\cmd+2p={<rel. energy>; <x el-spec>, <y el-spec>, <z el-spec>}+
+ \end{itemize}
+\end{framed}
+\cmd=<el-spec>= can have the values \cmd=pair=, \cmd=up= and \cmd=down= or can be left empty. \cmd=<rel. energy>= actually is the $y$ coordinate ansd shifts the AO vertically by \cmd=<rel. energy>= \si{\centi\metre}.
+
+The argument \cmd=<pos>= is important, when p orbitals are used. For instance compare the following example to the one before:
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+When both variants are used one can also see, that the right atom is shifted to the right (hence the naming). The right atom is shifted by \SI{4}{\centi\metre} per default and canbe adjusted individually, see page \pageref{option:distance}.
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+  \atom{right}{
+    1s = {  0; pair} ,
+    2s = {  1; pair} ,
+    2p = {1.5; up, down, }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+With the next command the reason for the shift becomes clear.
+
+\subsection{The \texttt{\textbackslash molecule} command}
+\begin{framed}
+ \cmd=\molecule[<name>]{<MO-spec>}=
+ \begin{itemize}\small
+  \item\cmd=<name>= (o) caption of the molekule
+  \item\cmd=<MO-spec>= (m) specifications of the molecular orbitals (MO)
+ \end{itemize}
+\end{framed}
+An example first:
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {  0; up} }
+  \atom{right}{ 1s = {  0; up} }
+  \molecule { 1sMO = {.75; pair, } }
+ \end{MOdiagram}
+\end{LTXexample}
+
+The command \cmd=\molecule= connects the AO with the bonding and anti-bondung MO. \cmd=\molecule= can only be used \emph{after} one has set \emph{both} atoms, since the orbitals, that should be connected, must be known.
+
+The argument \cmd=<MO-spec>= accepts a comma separated list of key/value pairs:
+\begin{framed}
+ \begin{itemize}
+  \item\cmd+1sMO={<energy gain>; <s el-spec>, <s* el-spec>}+ (connects the AO specified by \cmd=1s=)
+  \item\cmd+2sMO={<energy gain>; <s el-spec>, <s* el-spec>}+ (connects the AO specified by \cmd=2s=)
+  \item\cmd+2pMO={<s energy gain>, <p energy gain>; <s el-spec>, <py el-spec>, <pz el- spec>, <py* el-spec>, <pz* el-spec>, <s* el-spec>}+ (connects the AO specified by \cmd=2p=)
+ \end{itemize}
+\end{framed}
+Obviously the regarding AO must have been set in order to connect them. This for example won't work:
+\begin{lstlisting}
+ \begin{MOdiagram} 
+  \atom{left} { 1s = {  0; } }
+  \atom{right}{ 1s = {  0; } }
+  \molecule { 2sMO = {.75; , } }
+ \end{MOdiagram}
+\end{lstlisting}
+The value used in \cmd=<energy gain>= determines how many \si{\centi\metre} the bonding MO lies below the lower AO or how many \si{\centi\metre} the anti-bondung MO lies above the higher AO.
+% 
+\begin{LTXexample}[pos=b]
+ same level:
+ \begin{MOdiagram}
+  \atom{left} { 1s = {  0; up} }
+  \atom{right}{ 1s = {  0; up} }
+  \molecule { 1sMO = {.75; pair, } }
+ \end{MOdiagram}
+
+ different levels:
+ \begin{MOdiagram}
+  \atom{left} { 1s = {  0; up} }
+  \atom{right}{ 1s = {  1; up} }
+  \molecule { 1sMO = {.25; pair, } }
+ \end{MOdiagram}
+\end{LTXexample}
+% 
+Please be aware, that you have to specify \emph{two} such values with \cmd=2pMO=: the splitting of the \textsigma\ orbitals and the splitting of the \textpi\ orbitals.
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 2p = { 0; up, up , } }
+  \atom{right}{ 2p = { 1; up, up , } }
+  \molecule { 2pMO = { 1.5, .75; pair, up, up , , , } } 
+ \end{MOdiagram}
+\end{LTXexample}
+
+The complete MO diagram for triplett dioxygen now could look something like that:
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left}{
+    1s = {0;pair},
+    2s = {2;pair},
+    2p = {5;pair,up,up}
+  }
+  \atom{right}{
+    1s = {0;pair},
+    2s = {2;pair},
+    2p = {5;pair,up,up}
+  }
+  \molecule{
+    1sMO  = {.5;pair,pair},
+    2sMO  = {.5;pair,pair},
+    2pMO  = {1.5,.5;pair,pair,pair,up,up,}
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsection{The Naming Scheme}\label{Namensgebung}
+Since one wants to be able to put labels to the orbitals and since they are nodes in a tikzpicture, the internal naming scheme is important. It closely follows the function:
+\begin{center}
+\begin{MOdiagram}[distance=6cm,AO-width=20pt,labels-fs=\tt\footnotesize]
+ \atom{left}{
+   1s={0;},
+   2s={2;},
+   2p={5;,,},
+   label={ 1sleft={1sleft}, 2sleft={2sleft}, 2pxleft={2pxleft}, 2pyleft={2pyleft}, 2pzleft={2pzleft} }
+ }
+ \atom{right}{
+   1s={0;},
+   2s={2;},
+   2p={5;,,},
+   label={ 1sright={1sright}, 2sright={2sright}, 2pxright={2pxright}, 2pyright={2pyright}, 2pzright={2pzright} }
+ }
+ \molecule{
+   1sMO={.5;,},
+   2sMO={.5;,},
+   2pMO={1.5,.5;,,,,,},
+   label={ 1sigma={1sigma}, 1sigma*={1sigma*}, 2sigma={2sigma}, 2sigma*={2sigma*}, 2psigma={2psigma}, 2psigma*={2psigma*}, 2piy={2piy}, 2piy*={2piy*}, 2piz={2piz}, 2piz*={2piz*} }
+ }
+\end{MOdiagram}
+\end{center}
+With these names it is possible to reference the orbitals with the known \TikZ commands:
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0; } }
+  \atom{right}{ 1s = {0; } }
+  \molecule { 1sMO = {.75; , } }
+  \draw[<->,red,semithick] (1sigma) -- (1sigma*) ;
+  \draw[red] (1sigma*) ++ (2cm,.5cm) node {splitting} ;
+ \end{MOdiagram}
+\end{LTXexample}
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0; } }
+  \atom{right}{ 1s = {0; } }
+  \molecule { 1sMO = {.75; , } }
+  \draw[draw=blue,fill=blue!20,opacity=.5] (1sigma*) circle (8pt);
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsection{Placing AO and MO Arbitrarily}
+The standard orbitals are not always sufficient in order to draw a correct MO diagram. For example in the MO diagram of \ce{XeF2} one would need this part, that illustrates the interaction between the bonding and anti-bonding combination of two p orbitals of Flourine with one p orbital of Xenon:
+
+\begin{center}
+ \begin{MOdiagram}[names]
+ \atom[\lewis{0.,F}\hspace*{5mm}\lewis{4.,F}]{left}{}
+ \atom[Xe]{right}{}
+ \molecule[\ce{XeF2}]{}
+ \AO[a](1cm){s}{0;up}
+ \AO[b](1cm){s}{.25;up}
+ \AO[c](3cm){s}{-1;pair}
+ \AO[d](3cm){s}{0;pair}
+ \AO[e](3cm){s}{1.5;}
+ \AO[f](5cm){s}{1.25;pair}
+ \connect{ a & d , b & c , b & e , c & f , e & f }
+ \node[right,xshift=4mm] at (c) {\footnotesize bonding};
+ \node[above] at (d.90) {\footnotesize not bonding};
+ \node[above] at (e.90) {\footnotesize anti-bonding};
+\end{MOdiagram}
+\end{center}
+To create diagrams like this there is the following command, which draws a single AO:
+\begin{framed}
+ \cmd=\AO[<name>](<xshift>){<type>}{<energy>;<el-spec>}=
+ \begin{itemize}\small
+  \item\cmd=<name>= (o) name of the node
+  \item\cmd=<xshift>= (o) vertical position of the Orbitals, a \TeX\ dimension.
+  \item\cmd=<type>= (m) \cmd=s= or \cmd=p=
+  \item\cmd=<AO-spec>= (m) specification of the AO
+ \end{itemize}
+\end{framed}
+Depending on the \cmd=<type>= one s or three p porbitals are drawn.
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \AO{s}{0;}
+  \AO(-20pt){p}{1;pair,up,down}
+ \end{MOdiagram}
+\end{LTXexample}
+
+Please notice, that \cmd=<el-spec>= only awaits one specification with the type \cmd=s=, but three with the type \cmd=p=, separated with commas.
+
+If one wants to place such an AO at the position of an atom, one has to know their \cmd=<xshift>=. They have these predefined values (also see section \ref{orbital-positionen}):\label{xshift}
+\begin{itemize}
+ \item atom left: \SI{1}{\centi\metre}
+ \item molecule: \SI{3}{\centi\metre}
+ \item atom right: \SI{5}{\centi\metre}
+\end{itemize}
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} {1s={0;}}
+  \atom{right}{1s={0;}}
+  \molecule {1sMO={1;,}}
+  \AO(1cm){s}{2;pair}
+  \AO(3cm){s}{2;pair}
+  \AO(5cm){s}{2;pair}
+ \end{MOdiagram}
+\end{LTXexample}
+
+Within the p orbitals there is an additional shift by \SI{20}{pt} per orbital. This is equivalent to a double shift by the length \cmd=AO-width= (see section \ref{option:AO-width}):
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} {2p={0;,,}}
+  \atom{right}{2p={0;,,}}
+  % above the left atom:
+  \AO(1cm)     {s}{ .5;pair}
+  \AO(1cm-20pt){s}{  1;up}
+  \AO(1cm-40pt){s}{1,5;down}
+  % above the right atom:
+  \AO(5cm)     {s}{ .5;pair}
+  \AO(5cm+20pt){s}{  1;up}
+  \AO(5cm+40pt){s}{1.5;down}
+ \end{MOdiagram}
+\end{LTXexample}
+
+The AO created with \cmd=\AO= also can be connected. For this you can use the \TikZ command \cmd=\draw=, of course:
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \AO[a]{s}{0;} \AO[b](2cm){s}{1;}
+  \AO[c]{s}{2;} \AO[d](2cm){s}{1.5;}
+  \draw (a) -- (b) (c) -- (d);
+ \end{MOdiagram}
+\end{LTXexample}
+
+However, if you want the lines to be drawn in the same style as the ones created by \cmd=\molecule=\footnote{which can be customized, see page \pageref{option:lines}}, you should use the command \cmd=\connect=.
+\begin{framed}
+ \cmd=\connect{<AO-connect>}=
+ \begin{itemize}\small
+  \item\cmd=<AO-connect>= (m) comma separated list of node name pairs connected with \cmd=&=.
+ \end{itemize}
+\end{framed}
+This command expects a comma separated list of node name pairs, that are to be connected. The names have to be connected with a \cmd=&=:
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \AO[a]{s}{0;} \AO[b](2cm){s}{1;}
+  \AO[c]{s}{2;} \AO[d](2cm){s}{1.5;}
+  \connect{ a & b, c & d }
+ \end{MOdiagram}
+\end{LTXexample}
+
+Some things still need to be said: \cmd=\connect= adds the anchor \cmd=east= to the first name and the anchor \cmd=west= to the second one. This means a connection only makes sense from the left to the right. However, you can add own anchors using the usual \TikZ way:
+
+\begin{LTXexample}
+ \begin{tikzpicture}
+  \draw (0,0) node (a) {a} ++ (1,0) node (b) {b}
+        ++ (0,1) node (c) {c} ++ (-1,0) node (d) {d} ;
+  \connect{ a.90 & d.-90, c.180 & d.0 }
+ \end{tikzpicture}
+\end{LTXexample}
+
+
+\subsection{The Positioning Scheme}\label{orbital-positionen}
+The figure below shows the values of the $x$ coordinates of the orbitals, depending in the values of \cmd=<distance>= (\cmd=<dist>=) and \cmd=<AO-width>= (\cmd=<AO>=). In sections \ref{option:distance} and \ref{option:AO-width} these lengths and how they can be changed are discussed.
+
+\begin{MOdiagram}[distance=6cm,AO-width=25pt,labels-fs=\tt\footnotesize,labels-style={text width=40pt,align=center}]
+ \atom{left}{
+   1s={0;},
+   2s={3;},
+   2p={8;,,},
+   label={ 1sleft={1cm}, 2sleft={1cm}, 2pxleft={1cm}, 2pyleft={1cm - 2*<AO>}, 2pzleft={1cm - 4*<AO>} } }
+ \atom{right}{
+   1s={0;},
+   2s={3;},
+   2p={8;,,},
+   label={ 1sright={1cm + <dist>}, 2sright={1cm + <dist>}, 2pxright={1cm+ <dist>}, 2pyright={1cm + <dist> + 2*<AO>}, 2pzright={1cm + <dist> + 4*<AO>} } }
+ \molecule{
+   1sMO={.75;,},
+   2sMO={.75;,},
+   2pMO={3,1;,,,,,},
+   label={ 1sigma={.5*<dist> + 1cm}, 1sigma*={.5*<dist> + 1cm}, 2sigma={.5*<dist> + 1cm}, 2sigma*={.5*<dist> + 1cm}, 2psigma={.5*<dist> + 1cm}, 2psigma*={.5*<dist> + 1cm}, 2piy={.5*<dist> + 1cm - <AO>}, 2piy*={.5*<dist> + 1cm - <AO>}, 2piz={.5*<dist> + 1cm + <AO>}, 2piz*={.5*<dist> + 1cm + <AO>} }
+ }
+\end{MOdiagram}
+
+
+\section{Customization}
+\subsection{Environment Options}
+There are some options with which the layout of the MO diagrams can be changed:
+\begin{itemize}
+ \item\cmd+style=<type>+ change the style of the orbitals and the connecting lines, section \ref{option:style}.
+ \item\cmd+distance=<dim>+ distance betwen left and right atom, section \ref{option:distance}.
+ \item\cmd+AO-width=<dim>+ change the width of orbitals, section \ref{option:AO-width}.
+ \item\cmd+lines=<tikz>+ change the \TikZ style of the connecting lines, section \ref{option:lines}.
+ \item\cmd+names=<bool>+ add captions to the atoms and the molecule, section \ref{option:names}.
+ \item\cmd+labels=<bool>+ add default labels to the orbitals, section \ref{option:labels}.
+ \item\cmd+labels-fs=<cs>+ change the font size of the labels, section \ref{option:labels-fs}.
+ \item\cmd+labels-style=<tikz>+ change the \TikZ style of the labels, section \ref{option:labels-style}.
+\end{itemize}
+They all are discussed in the following sections. They are used either as option of the environment
+\begin{lstlisting}
+ \begin{MOdiagram}[<key = value>]
+  ...
+ \end{MOdiagram}
+\end{lstlisting}
+or as argument of the setup command
+\begin{framed}
+ \cmd+\MOsetup{<key = value>}+
+ \begin{itemize}\small
+  \item\cmd+<key = val>+ (m) comma separated key/value list
+ \end{itemize}
+\end{framed}
+
+\subsubsection{Option \texttt{style}}\label{option:style}
+There are four different styles, which can be chosen.
+\begin{itemize}
+ \item\cmd+style=plain+ \AOinline[style=plain]{pair} (default)
+ \item\cmd+style=square+ \AOinline[style=square]{pair}
+ \item\cmd+style=round+ \AOinline[style=round]{pair}
+ \item\cmd+style=fancy+ \AOinline[style=fancy]{pair}
+\end{itemize}
+Let's take the MO diagram of \ce{H2} to illustrate the different styles:
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=plain]% Default
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=square]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=round]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=fancy]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsubsection{Option \texttt{distance}}\label{option:distance}
+Depending on labels and captions the \SI{4}{\centi\metre} by which the right and left atom are separated can be too small. With \cmd+distance=<dim>+ the length can be adjusted. With this, the position of the right atom is changed to \cmd=1cm + <dim>= and the position of the molecule is changed to \cmd=0.5*(1cm + <dim>)=, also see page Seite \pageref{xshift} and section \ref{orbital-positionen}.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[distance=6cm]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsubsection{Option \texttt{AO-width}}\label{option:AO-width}
+The length \cmd=AO-width= sets the length of the horizontal line in a orbital displayed with the \cmd=plain= style. It's default value is \SI{10}{pt}.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[AO-width=15pt]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[style=fancy,AO-width=15pt]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+By changing the value of \cmd=AO-width= the positions of the p and the \textpi\ orbitals also change, see section \ref{orbital-positionen}.
+
+\subsubsection{Option \texttt{lines}}\label{option:lines}
+The option \cmd=lines= can be used to modify the \TikZ style of the connecting lines:
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[lines={gray,thin}]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsubsection{Option \texttt{names}}\label{option:names}
+If you use the option \cmd=names=, the atoms and the molecule get captions, if you have used the optional \cmd=<name>= argument of \cmd=\atom= and/or \cmd=\molecule=.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[names]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsubsection{Option \texttt{labels}}\label{option:labels}
+If you use the option \cmd=labels=, predefined labels are written below the orbitals. These labels can be changed, see section \ref{key:label}.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsubsection{Option \texttt{labels-fs}}\label{option:labels-fs}
+Labels are set with the font size \cmd=\small=. If you want to change that, you can use the option \cmd=labels-fs=.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels,labels-fs=\footnotesize]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+This also allows you to change the font style or font shape of the labels.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels,labels-fs=\sffamily\footnotesize]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsubsection{Option \texttt{labels-style}}\label{option:labels-style}
+The option \cmd=labels-style= changes the \TikZ style of the nodes, within which the labels are written.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels,labels-style={blue}]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{ 1sMO = {.75;pair,} }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsection{\texttt{\textbackslash atom} and \texttt{\textbackslash molecule} Specific Customizations}
+\subsubsection{The \texttt{label} Key}\label{key:label}
+If you don't want to use the predefined labels, change single labels or use only one or two labels, you can use the key \cmd=label=. This key is used in the \cmd=\atom= and  \cmd=\molecule= commands in the \cmd=<AO-spec>= or \cmd=<MO-spec>= argument, respectively. The key awaits a comma separated key/value list. The names mentioned in section \ref{Namensgebung} are used as keys to specify the AO, that you want to label.
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels-fs=\footnotesize]
+  \atom[H]{left} { 1s = {0;up} }
+  \atom[H]{right}{ 1s = {0;up} }
+  \molecule[\ce{H2}]{
+    1sMO  = {.75;pair,},
+    label = { 1sigma = {bonding MO} }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ \begin{MOdiagram}[style=square,distance=6cm]
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{
+    1sMO  = {.75;pair,} ,
+    label = {
+      1sigma  = $\sigma$,
+      1sigma* = $\sigma^*$
+    }
+  }
+  \node[right] at (1sigma.-45) {bonding};
+  \node[right] at (1sigma*.45) {anti-bonding};
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsubsection{The \texttt{color} Key}\label{key:color}
+Analogous to the \cmd=label= key the \cmd=color= key can be used to display coloured electrons:
+
+\begin{LTXexample}
+ % use package 'mhchem'
+ \begin{MOdiagram}[labels-fs=\footnotesize]
+  \atom[H]{left}{
+    1s = {0;pair},
+    color = { 1sleft = blue }
+  }
+  \atom[H]{right}{
+    1s = {0;pair},
+    color = { 1sright = red }
+  }
+  \molecule[\ce{H2}]{
+    1sMO  = {.75;pair,pair},
+    label = { 1sigma = {bonding MO} },
+    color = { 1sigma = green, 1sigma* = cyan }
+  }
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsection{Energy Axis}
+Last but not least one might want to add an energy axis to the diagram. For this there is the command \cmd=\EnergyAxis=.
+\begin{framed}
+ \cmd+\EnergyAxis[<key = val>]+
+ \begin{itemize}\small
+  \item\cmd+<key = val>+ (o) key/value pairs to modify the axis
+ \end{itemize}
+\end{framed}
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{ 1sMO = {.75;pair,} }
+  \EnergyAxis
+ \end{MOdiagram}
+\end{LTXexample}
+
+For the time beeing there are two keys to modify the axis.
+\begin{framed}
+ \begin{itemize}
+  \item\cmd+title=<title>+ axis label (default: \cmd=energy=).
+  \item\cmd+head=<tikz-arrow-head>+ arrow head; you can use the arrow heads specified in the \TikZ library \paket{arrows} (pgfmanual v2.10 pages 256ff.) (default: \cmd=>=).
+ \end{itemize}
+\end{framed}
+
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{ 1sMO = {.75;pair,} }
+  \EnergyAxis[title]
+ \end{MOdiagram}
+\end{LTXexample}
+\begin{LTXexample}
+ \begin{MOdiagram}
+  \atom{left} { 1s = {0;up} }
+  \atom{right}{ 1s = {0;up} }
+  \molecule{ 1sMO = {.75;pair,} }
+  \EnergyAxis[title=E,head=stealth]
+ \end{MOdiagram}
+\end{LTXexample}
+
+
+\subsection{Examples}
+% 
+\begin{LTXexample}[pos=b]
+ % use packages 'mhchem' (and 'textgreek' loaded by 'MOdiagram')
+ \begin{figure}
+  \centering
+  \begin{MOdiagram}[style=square,labels,names,AO-width=8pt,labels-fs=\footnotesize]
+   \atom[\ce{O_a}]{left}{
+     1s = {0;pair},
+     2s = {2;pair},
+     2p = {5;pair,up,up}
+   }
+   \atom[\ce{O_b}]{right}{
+     1s = {0;pair},
+     2s = {2;pair},
+     2p = {5;pair,up,up}
+   }
+   \molecule[\ce{O2}]{
+     1sMO  = {.5;pair,pair},
+     2sMO  = {.5;pair,pair},
+     2pMO  = {1.5,.5;pair,pair,pair,up,up,},
+     color = { 2piy*=red, 2piz*=red }
+   }
+   \EnergyAxis
+  \end{MOdiagram}
+  \caption{MO diagram of $^3$\textSigma-\ce{O2}.}
+ \end{figure}
+\end{LTXexample}
+\begin{LTXexample}[pos=b]
+ % use package 'chemfig'
+ \begin{figure}
+  \centering
+  \begin{MOdiagram}[style=fancy,distance=7cm,AO-width=15pt,labels]
+   \atom[N]{left}{
+     2p = {0;up,up,up}
+   }
+   \atom[O]{right}{
+     2p = {2;pair,up,up}
+   }
+   \molecule[NO]{
+     2pMO = {1.8,.4;pair,pair,pair,up,,},
+     color = { 2piy*=red }
+   }
+   \EnergyAxis[title]
+  \end{MOdiagram}
+  \caption{Part of the MO diagram of \protect\Lewis{4.,NO}.}
+ \end{figure}
+\end{LTXexample}
+% 
+
+\end{document}
\ No newline at end of file
diff --git a/Master/texmf-dist/tex/latex/modiagram/modiagram.sty b/Master/texmf-dist/tex/latex/modiagram/modiagram.sty
new file mode 100644
index 00000000000..d3db03f942b
--- /dev/null
+++ b/Master/texmf-dist/tex/latex/modiagram/modiagram.sty
@@ -0,0 +1,1294 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% --------------------------------------------------------------------------- %
+% - MOdiagram - modiagram.sty                                               - %
+% - easy creation of molecular orbital diagrams                             - %
+% --------------------------------------------------------------------------- %
+% - Clemens Niederberger                                                    - %
+% - 2011/09/25                                                              - %
+% --------------------------------------------------------------------------- %
+% - http://www.mychemistry.eu/                                              - %
+% - contact@mychemistry.eu                                                  - %
+% --------------------------------------------------------------------------- %
+% - If you have any ideas, questions, suggestions or bugs to report, please - %
+% - feel free to contact me.                                                - %
+% --------------------------------------------------------------------------- %
+% - Copyright 2011 Clemens Niederberger                                     - %
+% -                                                                         - %
+% - This work may be distributed and/or modified under the                  - %
+% - conditions of the LaTeX Project Public License, either version 1.3      - %
+% - of this license or (at your option) any later version.                  - %
+% - The latest version of this license is in                                - %
+% -   http://www.latex-project.org/lppl.txt                                 - %
+% - and version 1.3 or later is part of all distributions of LaTeX          - %
+% - version 2005/12/01 or later.                                            - %
+% -                                                                         - %
+% - This work has the LPPL maintenance status `maintained'.                 - %
+% -                                                                         - %
+% - The Current Maintainer of this work is Clemens Niederberger.            - %
+% -                                                                         - %
+% - This work consists of the files modiagram.sty, modiagram_doc_de.tex,    - %
+% - modiagram_doc_de.tex, README                                            - %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\RequirePackage{ expl3 , xparse , l3keys2e , tikz , textgreek , amsmath }
+\usetikzlibrary{calc,arrows}
+\ProvidesExplPackage {modiagram} {2011/09/25} {0.1} {easy creation of molecular orbital diagrams}
+
+% --------------------------------------------------------------------------- %
+% error messages
+\msg_set:nnn { MOdiagram } { missing-atom }
+  {
+    You~need~to~specify~the~left~and~right~atom~first~before~you~can~use~
+    \token_to_str:N \molecule \c_space_tl \msg_line_context: .
+  }
+
+\msg_set:nnn { MOdiagram } { missing-AO }
+  {
+    You~need~to~specify~both~#2~AOs~first~before~you~can~use~
+    #1~ \msg_line_context: .
+  }
+
+% --------------------------------------------------------------------------- %
+% main environment
+\NewDocumentEnvironment { MOdiagram } { o g }
+  {
+    \dim_gzero:N \g_MOdiagram_min_energy_dim
+    \dim_gzero:N \g_MOdiagram_max_energy_dim
+    \IfNoValueF { #1 } { \keys_set:nn { MOdiagram / diagram } { #1 } }
+    \MOdiagram_set_labels:
+    \MOdiagram_tikzpicture:n { }
+  }
+  {
+    \bool_if:NT \l_MOdiagram_names_bool
+      {
+        \MOdiagram_node:n { below }
+          at
+          (
+            \l_MOdiagram_left_atom_position_dim ,
+            \g_MOdiagram_min_energy_dim - 1cm
+          )
+          { \smash[b] { \tl_use:N \l_MOdiagram_atom_left_name_tl } } ;
+        \MOdiagram_node:n { below }
+          at
+          (
+            \l_MOdiagram_molecule_position_dim ,
+            \g_MOdiagram_min_energy_dim - 1cm
+          )
+          { \smash[b] { \tl_use:N \l_MOdiagram_molecule_name_tl } } ;
+        \MOdiagram_node:n { below }
+          at
+          (
+            \l_MOdiagram_left_atom_position_dim
+              + \l_MOdiagram_inter_atom_distance_dim ,
+            \g_MOdiagram_min_energy_dim - 1cm
+          )
+          { \smash[b] { \tl_use:N \l_MOdiagram_atom_right_name_tl } } ;
+      }
+    \endtikzpicture
+  }
+
+\bool_new:N \l_MOdiagram_AO_square_bool
+\bool_new:N \l_MOdiagram_AO_round_bool
+\bool_new:N \l_MOdiagram_AO_fancy_bool
+\bool_new:N \l_MOdiagram_AO_labels_bool
+\bool_new:N \l_MOdiagram_names_bool
+
+\tl_new:N \l_MOdiagram_lines_tl
+\tl_set:Nn \l_MOdiagram_lines_tl { dotted }
+
+\tl_new:N \l_MOdiagram_orbital_label_fontsize_tl
+\tl_new:N \l_MOdiagram_orbital_label_style_tl
+
+\dim_new:N \l_MOdiagram_AO_width_dim
+\dim_set:Nn \l_MOdiagram_AO_width_dim { 10pt }
+
+\dim_new:N \l_MOdiagram_left_atom_position_dim
+\dim_set:Nn \l_MOdiagram_left_atom_position_dim { 1cm }
+\dim_new:N \l_MOdiagram_inter_atom_distance_dim
+\dim_set:Nn \l_MOdiagram_inter_atom_distance_dim { 4cm }
+\dim_new:N \l_MOdiagram_molecule_position_dim
+
+\dim_new:N \g_MOdiagram_min_energy_dim
+\dim_new:N \g_MOdiagram_max_energy_dim
+
+\cs_new_nopar:Npn \MOdiagram_energy_range:N #1
+  {
+    \dim_set:Nn \l_tmpa_dim { #1 }
+    \dim_compare:nT { \l_tmpa_dim < \g_MOdiagram_min_energy_dim }
+      { \dim_gset_eq:NN \g_MOdiagram_min_energy_dim \l_tmpa_dim }
+    \dim_compare:nT { \l_tmpa_dim > \g_MOdiagram_max_energy_dim }
+      { \dim_gset_eq:NN \g_MOdiagram_max_energy_dim \l_tmpa_dim }
+  }
+\cs_generate_variant:Nn \MOdiagram_energy_range:N { n }
+
+\cs_new_nopar:Npn \MOdiagram_molecule_position:n #1
+  {
+    \fp_set_from_dim:Nn \l_tmpa_tl { #1 }
+    \fp_mul:Nn \l_tmpa_tl { .5 }
+    \dim_set:Nn \l_MOdiagram_molecule_position_dim
+      { \fp_to_dim:N \l_tmpa_tl + \l_MOdiagram_left_atom_position_dim }
+  }
+\cs_generate_variant:Nn \MOdiagram_molecule_position:n { f }
+
+\MOdiagram_molecule_position:f
+  { \dim_use:N \l_MOdiagram_inter_atom_distance_dim }
+
+\keys_define:nn { MOdiagram / diagram }
+  {
+    style          .choice: ,
+    style / plain  .code:n    =
+      {
+        \bool_set_false:N \l_MOdiagram_AO_square_bool
+        \bool_set_false:N \l_MOdiagram_AO_round_bool
+        \bool_set_false:N \l_MOdiagram_AO_fancy_bool
+        \tl_set:Nn \l_MOdiagram_lines_tl { dotted }
+      } ,
+    style / square .code:n    =
+      {
+        \bool_set_true:N \l_MOdiagram_AO_square_bool
+        \bool_set_false:N \l_MOdiagram_AO_round_bool
+        \bool_set_false:N \l_MOdiagram_AO_fancy_bool
+        \tl_set:Nn \l_MOdiagram_lines_tl { gray }
+      } ,
+    style / round  .code:n    =
+      {
+        \bool_set_true:N \l_MOdiagram_AO_square_bool
+        \bool_set_true:N \l_MOdiagram_AO_round_bool
+        \bool_set_false:N \l_MOdiagram_AO_fancy_bool
+        \tl_set:Nn \l_MOdiagram_lines_tl { gray }
+      } ,
+    style / fancy  .code:n    =
+      {
+        \bool_set_true:N \l_MOdiagram_AO_square_bool
+        \bool_set_true:N \l_MOdiagram_AO_round_bool
+        \bool_set_true:N \l_MOdiagram_AO_fancy_bool
+        \tl_set:Nn \l_MOdiagram_lines_tl { densely~dashed }
+      } ,
+    lines         .tl_set:N   = \l_MOdiagram_lines_tl ,
+    distance      .code:n     =
+      {
+        \dim_set:Nn \l_MOdiagram_inter_atom_distance_dim { #1 }
+        \MOdiagram_molecule_position:n { #1 }
+      } ,
+    AO-width      .tl_set:N   = \l_MOdiagram_AO_width_dim ,
+    labels        .bool_set:N = \l_MOdiagram_AO_labels_bool ,
+    names         .bool_set:N = \l_MOdiagram_names_bool ,
+    labels-fs     .tl_set:N   = \l_MOdiagram_orbital_label_fontsize_tl ,
+    labels-style  .tl_set:N   = \l_MOdiagram_orbital_label_style_tl
+  }
+
+% --------------------------------------------------------------------------- %
+% setup command
+\NewDocumentCommand \MOsetup { m }
+  { \keys_set:nn { MOdiagram / diagram } { #1 } \tex_unskip:D }
+
+% --------------------------------------------------------------------------- %
+% draw AOs
+\tl_new:N \l_MOdiagram_atom_left_name_tl
+\tl_new:N \l_MOdiagram_atom_right_name_tl
+
+\bool_new:N \l_MOdiagram_left_atom_placed_bool
+\bool_set_false:N \l_MOdiagram_left_atom_placed_bool
+\bool_new:N \l_MOdiagram_right_atom_placed_bool
+\bool_set_false:N \l_MOdiagram_right_atom_placed_bool
+
+\NewDocumentCommand \atom { o m m }
+  {
+    \MOdiagram_atom_disable:
+    \keys_set:nn { MOdiagram / atom } { position = #2 }
+    \keys_set:nn { MOdiagram / atom } { #3 }
+    \bool_if:NTF \l_MOdiagram_atom_left_bool
+      { \bool_set_true:N \l_MOdiagram_left_atom_placed_bool }
+      { \bool_set_true:N \l_MOdiagram_right_atom_placed_bool }
+    \IfNoValueF { #1 }
+      {
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          { \tl_set:Nn \l_MOdiagram_atom_left_name_tl { #1 } }
+          { \tl_set:Nn \l_MOdiagram_atom_right_name_tl { #1 } }
+      }
+    \MOdiagram_one_s:
+    \MOdiagram_two_s:
+    \MOdiagram_two_p:
+%     \MOdiagram_three_s:
+%     \MOdiagram_three_p:
+%     \MOdiagram_four_s:
+  }
+
+\bool_new:N \l_MOdiagram_atom_left_bool
+
+\keys_define:nn { MOdiagram / atom }
+  {
+    position         .choice: ,
+    position / left  .code:n =
+      { \bool_set_true:N \l_MOdiagram_atom_left_bool } ,
+    position / right .code:n =
+      { \bool_set_false:N \l_MOdiagram_atom_left_bool }
+  }
+
+\dim_new:N \l_MOdiagram_atom_xshift_dim
+
+\keys_define:nn { MOdiagram / atom }
+  {
+    1s    .code:n = { \MOdiagram_one_s_set:n #1 \q_stop } ,
+    2s    .code:n = { \MOdiagram_two_s_set:n #1 \q_stop } ,
+    2p    .code:n = { \MOdiagram_two_p_set:n #1 \q_stop } ,
+    color .code:n = { \MOdiagram_electron_color_set:n { #1 } } ,
+    label .code:n = { \MOdiagram_orbital_label_set:n { #1 } }
+  }
+
+% --------------------------------------------------------------------------- %
+% 1s orbital
+\dim_new:N \l_MOdiagram_atom_one_s_dim
+\dim_new:N \l_MOdiagram_atom_left_one_s_dim
+\dim_new:N \l_MOdiagram_atom_right_one_s_dim
+
+\tl_new:N \l_MOdiagram_AO_one_s_electron_tl
+
+\bool_new:N \l_MOdiagram_atom_one_s_bool
+\bool_new:N \l_MOdiagram_one_s_left_bool
+\bool_set_false:N \l_MOdiagram_one_s_left_bool
+\bool_new:N \l_MOdiagram_one_s_right_bool
+\bool_set_false:N \l_MOdiagram_one_s_right_bool
+
+\cs_new_nopar:Npn \MOdiagram_one_s_set:n #1;#2 \q_stop
+  {
+    \bool_set_true:N \l_MOdiagram_atom_one_s_bool
+    \dim_set:Nn \l_MOdiagram_atom_one_s_dim { #1 cm }
+    \tl_set:Nn \l_MOdiagram_AO_one_s_electron_tl { #2 }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_one_s:
+  {
+    \bool_if:NT \l_MOdiagram_atom_one_s_bool
+      {
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          {
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_xshift_dim
+              \l_MOdiagram_left_atom_position_dim
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_left_one_s_dim
+              \l_MOdiagram_atom_one_s_dim
+            \bool_set_true:N \l_MOdiagram_one_s_left_bool
+          }
+          {
+            \dim_set:Nn \l_MOdiagram_atom_xshift_dim
+              {
+                \l_MOdiagram_left_atom_position_dim
+                  + \l_MOdiagram_inter_atom_distance_dim
+              }
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_right_one_s_dim
+              \l_MOdiagram_atom_one_s_dim
+            \bool_set_true:N \l_MOdiagram_one_s_right_bool
+          }
+        \MOdiagram_energy_range:N \l_MOdiagram_atom_one_s_dim
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (1s
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { left }
+              { right }
+          )
+          at ( \l_MOdiagram_atom_xshift_dim , \l_MOdiagram_atom_one_s_dim )
+          {
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { \MOdiagram_get_electron_color:n { 1sleft } }
+              { \MOdiagram_get_electron_color:n { 1sright } }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_AO_one_s_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          { \MOdiagram_get_orbital_label:n { 1s left } }
+          { \MOdiagram_get_orbital_label:n { 1s right } }
+      }
+  }
+
+% --------------------------------------------------------------------------- %
+% 2s orbital
+\dim_new:N \l_MOdiagram_atom_two_s_dim
+\dim_new:N \l_MOdiagram_atom_left_two_s_dim
+\dim_new:N \l_MOdiagram_atom_right_two_s_dim
+
+\tl_new:N \l_MOdiagram_AO_two_s_electron_tl
+
+\bool_new:N \l_MOdiagram_atom_two_s_bool
+\bool_new:N \l_MOdiagram_two_s_left_bool
+\bool_set_false:N \l_MOdiagram_two_s_left_bool
+\bool_new:N \l_MOdiagram_two_s_right_bool
+\bool_set_false:N \l_MOdiagram_two_s_right_bool
+
+\cs_new_nopar:Npn \MOdiagram_two_s_set:n #1;#2 \q_stop
+  {
+    \bool_set_true:N \l_MOdiagram_atom_two_s_bool
+    \dim_set:Nn \l_MOdiagram_atom_two_s_dim { #1 cm }
+    \tl_set:Nn \l_MOdiagram_AO_two_s_electron_tl { #2 }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_two_s:
+  {
+    \bool_if:NT \l_MOdiagram_atom_two_s_bool
+      {
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          {
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_xshift_dim
+              \l_MOdiagram_left_atom_position_dim
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_left_two_s_dim
+              \l_MOdiagram_atom_two_s_dim
+            \bool_set_true:N \l_MOdiagram_two_s_left_bool
+          }
+          {
+            \dim_set:Nn \l_MOdiagram_atom_xshift_dim
+              {
+                \l_MOdiagram_left_atom_position_dim
+                  + \l_MOdiagram_inter_atom_distance_dim
+              }
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_right_two_s_dim
+              \l_MOdiagram_atom_two_s_dim
+            \bool_set_true:N \l_MOdiagram_two_s_right_bool
+          }
+        \MOdiagram_energy_range:N \l_MOdiagram_atom_two_s_dim
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2s
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { left }
+              { right }
+          )
+          at ( \l_MOdiagram_atom_xshift_dim , \l_MOdiagram_atom_two_s_dim )
+          {
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { \MOdiagram_get_electron_color:n { 2sleft } }
+              { \MOdiagram_get_electron_color:n { 2sright } }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_AO_two_s_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          { \MOdiagram_get_orbital_label:n { 2s left } }
+          { \MOdiagram_get_orbital_label:n { 2s right } }
+      }
+  }
+
+% --------------------------------------------------------------------------- %
+% 2p orbital
+\dim_new:N \l_MOdiagram_atom_two_p_dim
+\dim_new:N \l_MOdiagram_atom_left_two_p_dim
+\dim_new:N \l_MOdiagram_atom_right_two_p_dim
+
+\dim_new:N \l_MOdiagram_atom_px_shift_dim
+\dim_new:N \l_MOdiagram_atom_py_shift_dim
+\dim_new:N \l_MOdiagram_atom_pz_shift_dim
+
+\tl_new:N \l_MOdiagram_AO_two_px_electron_tl
+\tl_new:N \l_MOdiagram_AO_two_py_electron_tl
+\tl_new:N \l_MOdiagram_AO_two_pz_electron_tl
+
+\bool_new:N \l_MOdiagram_atom_two_p_bool
+\bool_new:N \l_MOdiagram_two_p_left_bool
+\bool_set_false:N \l_MOdiagram_two_p_left_bool
+\bool_new:N \l_MOdiagram_two_p_right_bool
+\bool_set_false:N \l_MOdiagram_two_p_right_bool
+
+\cs_new_nopar:Npn \MOdiagram_two_p_set:n #1;#2,#3,#4 \q_stop
+  {
+    \bool_set_true:N \l_MOdiagram_atom_two_p_bool
+    \dim_set:Nn \l_MOdiagram_atom_two_p_dim { #1 cm }
+    \tl_set:Nn \l_MOdiagram_AO_two_px_electron_tl { #2 }
+    \tl_set:Nn \l_MOdiagram_AO_two_py_electron_tl { #3 }
+    \tl_set:Nn \l_MOdiagram_AO_two_pz_electron_tl { #4 }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_p_orbitals_shift:nnn #1#2#3
+  {
+    \fp_set_from_dim:Nn \l_tmpa_tl { \l_MOdiagram_AO_width_dim } 
+    {
+      \fp_mul:Nn \l_tmpa_tl { #1 }
+      \dim_gset:Nn \l_MOdiagram_atom_px_shift_dim { \fp_to_dim:N \l_tmpa_tl }
+    }
+    {
+      \fp_mul:Nn \l_tmpa_tl { #2 }
+      \dim_gset:Nn \l_MOdiagram_atom_py_shift_dim { \fp_to_dim:N \l_tmpa_tl }
+    }
+    {
+      \fp_mul:Nn \l_tmpa_tl { #3 }
+      \dim_gset:Nn \l_MOdiagram_atom_pz_shift_dim { \fp_to_dim:N \l_tmpa_tl }
+    }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_two_p:
+  {
+    \bool_if:NT \l_MOdiagram_atom_two_p_bool
+      {
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          {
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_xshift_dim
+              \l_MOdiagram_left_atom_position_dim 
+            \MOdiagram_p_orbitals_shift:nnn { -4 } { -2 } { 0 }
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_left_two_p_dim
+              \l_MOdiagram_atom_two_p_dim
+            \dim_set_eq:NN
+              \l_energy_axis_dim
+              \l_MOdiagram_atom_px_shift_dim
+            \bool_set_true:N \l_MOdiagram_two_p_left_bool
+          }
+          {
+            \dim_set:Nn \l_MOdiagram_atom_xshift_dim
+              {
+                \l_MOdiagram_left_atom_position_dim
+                  + \l_MOdiagram_inter_atom_distance_dim
+              }
+            \MOdiagram_p_orbitals_shift:nnn { 0 } { 2 } { 4 }
+            \dim_set_eq:NN
+              \l_MOdiagram_atom_right_two_p_dim
+              \l_MOdiagram_atom_two_p_dim
+            \bool_set_true:N \l_MOdiagram_two_p_right_bool
+          }
+        \MOdiagram_energy_range:N \l_MOdiagram_atom_two_p_dim
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2pz
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { left }
+              { right }
+          )
+          at
+          (
+            \l_MOdiagram_atom_xshift_dim + \l_MOdiagram_atom_pz_shift_dim ,
+            \l_MOdiagram_atom_two_p_dim
+          )
+          {
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { \MOdiagram_get_electron_color:n { 2pz left } }
+              { \MOdiagram_get_electron_color:n { 2pz right } }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_AO_two_pz_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          { \MOdiagram_get_orbital_label:n { 2pz left } }
+          { \MOdiagram_get_orbital_label:n { 2pz right } }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2py
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { left }
+              { right }
+          )
+          at
+          (
+            \l_MOdiagram_atom_xshift_dim + \l_MOdiagram_atom_py_shift_dim ,
+            \l_MOdiagram_atom_two_p_dim
+          )
+          {
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { \MOdiagram_get_electron_color:n { 2py left } }
+              { \MOdiagram_get_electron_color:n { 2py right } }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_AO_two_py_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          { \MOdiagram_get_orbital_label:n { 2py left } }
+          { \MOdiagram_get_orbital_label:n { 2py right } }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2px
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { left }
+              { right }
+          )
+          at
+          (
+            \l_MOdiagram_atom_xshift_dim + \l_MOdiagram_atom_px_shift_dim ,
+            \l_MOdiagram_atom_two_p_dim
+          )
+          {
+            \bool_if:NTF \l_MOdiagram_atom_left_bool
+              { \MOdiagram_get_electron_color:n { 2px left } }
+              { \MOdiagram_get_electron_color:n { 2px right } }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_AO_two_px_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \bool_if:NTF \l_MOdiagram_atom_left_bool
+          { \MOdiagram_get_orbital_label:n { 2px left } }
+          { \MOdiagram_get_orbital_label:n { 2px right } }
+      }  
+  }
+
+% --------------------------------------------------------------------------- %
+% draw MOs
+\tl_new:N \l_MOdiagram_molecule_name_tl
+
+\NewDocumentCommand \molecule { o m }
+  {
+    \bool_if:nTF
+      {
+        \l_MOdiagram_left_atom_placed_bool
+          &&
+        \l_MOdiagram_right_atom_placed_bool
+      }
+      {
+        \MOdiagram_molecule_disable:
+        \keys_set:nn { MOdiagram / molecule } { #2 }
+        \IfNoValueF { #1 }
+          { \tl_set:Nn \l_MOdiagram_molecule_name_tl { #1 } }
+        \MOdiagram_one_mo_s:
+        \MOdiagram_two_mo_s:
+        \MOdiagram_two_mo_p:
+%         \MOdiagram_three_mo_s:
+%         \MOdiagram_three_mo_p:
+%         \MOdiagram_four_mo_s:
+      }
+      { \msg_error:nn { MOdiagram } { missing-atom } }
+  }
+
+\keys_define:nn { MOdiagram / molecule }
+  {
+    1sMO  .code:n = { \MOdiagram_one_mo_s_set:n #1 \q_stop } ,
+    2sMO  .code:n = { \MOdiagram_two_mo_s_set:n #1 \q_stop } ,
+    2pMO  .code:n = { \MOdiagram_two_mo_p_set:n #1 \q_stop } ,
+    color .code:n = { \MOdiagram_electron_color_set:n { #1 } } ,
+    label .code:n = { \MOdiagram_orbital_label_set:n { #1 } }
+  }
+
+% --------------------------------------------------------------------------- %
+% 1sigma orbitals
+\dim_new:N \l_MOdiagram_molecule_one_sigma_dim
+\dim_new:N \l_MOdiagram_molecule_one_sigmas_dim
+
+\tl_new:N \l_MOdiagram_MO_one_sigma_s_electron_tl
+\tl_new:N \l_MOdiagram_MO_one_sigmas_s_electron_tl
+\bool_new:N \l_MOdiagram_molecule_one_mo_s_bool
+
+\cs_new_nopar:Npn \MOdiagram_one_mo_s_set:n #1;#2,#3 \q_stop
+  {
+    \bool_set_true:N \l_MOdiagram_molecule_one_mo_s_bool
+    \tl_set:Nn \l_MOdiagram_MO_one_sigma_s_electron_tl { #2 }
+    \tl_set:Nn \l_MOdiagram_MO_one_sigmas_s_electron_tl { #3 }
+    \dim_set:Nn \l_MOdiagram_molecule_one_sigma_dim { #1 cm }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_one_mo_s:
+  {
+    \bool_if:NT \l_MOdiagram_molecule_one_mo_s_bool
+      {
+        \bool_if:nF
+          { \l_MOdiagram_one_s_left_bool && \l_MOdiagram_one_s_right_bool }
+          { \msg_error:nnxx { MOdiagram } { missing-AO } { 1sMO } { 1s } }
+        \MOdiagram_energy_range:n
+          {
+            \l_MOdiagram_atom_left_one_s_dim
+              - \l_MOdiagram_molecule_one_sigma_dim
+          }
+        \MOdiagram_energy_range:n
+          {
+            \l_MOdiagram_atom_right_one_s_dim
+              + \l_MOdiagram_molecule_one_sigma_dim
+          }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (1sigma)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim ,
+            \l_MOdiagram_atom_left_one_s_dim
+              - \l_MOdiagram_molecule_one_sigma_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 1sigma }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_one_sigma_s_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 1sigma }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (1sigma*)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim ,
+            \l_MOdiagram_atom_right_one_s_dim
+              + \l_MOdiagram_molecule_one_sigma_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 1sigma* }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_one_sigmas_s_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 1sigma* }
+        \MOdiagram_draw:f
+          { \l_MOdiagram_lines_tl }
+          (1s left.east)  -- (1sigma.west)  (1sigma.east)   -- (1s right.west)
+          (1s left.east)  -- (1sigma*.west) (1sigma*.east)  -- (1s right.west) ;
+      }
+  }
+
+% --------------------------------------------------------------------------- %
+% 2sigma orbitals
+\dim_new:N \l_MOdiagram_molecule_two_sigma_dim
+\dim_new:N \l_MOdiagram_molecule_two_sigmas_dim
+
+\tl_new:N \l_MOdiagram_MO_two_sigma_s_electron_tl
+\tl_new:N \l_MOdiagram_MO_two_sigmas_s_electron_tl
+\bool_new:N \l_MOdiagram_molecule_two_mo_s_bool
+
+\cs_new_nopar:Npn \MOdiagram_two_mo_s_set:n #1;#2,#3 \q_stop
+  {
+    \bool_set_true:N \l_MOdiagram_molecule_two_mo_s_bool
+    \tl_set:Nn \l_MOdiagram_MO_two_sigma_s_electron_tl { #2 }
+    \tl_set:Nn \l_MOdiagram_MO_two_sigmas_s_electron_tl { #3 }
+    \dim_set:Nn \l_MOdiagram_molecule_two_sigma_dim { #1 cm }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_two_mo_s:
+  {
+    \bool_if:NT \l_MOdiagram_molecule_two_mo_s_bool
+      {
+        \bool_if:nF
+          { \l_MOdiagram_two_s_left_bool && \l_MOdiagram_two_s_right_bool }
+          { \msg_error:nnxx { MOdiagram } { missing-AO } { 2sMO } { 2s } }
+        \MOdiagram_energy_range:n
+          {
+            \l_MOdiagram_atom_left_two_s_dim
+              - \l_MOdiagram_molecule_two_sigma_dim
+          }
+        \MOdiagram_energy_range:n
+          {
+            \l_MOdiagram_atom_right_two_s_dim
+              + \l_MOdiagram_molecule_two_sigma_dim
+          }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2sigma)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim ,
+            \l_MOdiagram_atom_left_two_s_dim
+              - \l_MOdiagram_molecule_two_sigma_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2sigma }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_sigma_s_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2sigma }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2sigma*)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim ,
+            \l_MOdiagram_atom_right_two_s_dim
+              + \l_MOdiagram_molecule_two_sigma_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2sigma* }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_sigmas_s_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2sigma* }
+        \MOdiagram_draw:f
+          { \l_MOdiagram_lines_tl }
+          (2s left.east)  -- (2sigma.west)  (2sigma.east)   -- (2s right.west)
+          (2s left.east)  -- (2sigma*.west) (2sigma*.east)  -- (2s right.west) ;
+      }
+  }
+
+% --------------------------------------------------------------------------- %
+% 2sigma orbitals
+\dim_new:N \l_MOdiagram_molecule_two_psigma_dim
+\dim_new:N \l_MOdiagram_molecule_two_ppi_dim
+
+\tl_new:N \l_MOdiagram_MO_two_sigma_p_electron_tl
+\tl_new:N \l_MOdiagram_MO_two_sigmas_p_electron_tl
+\tl_new:N \l_MOdiagram_MO_two_piy_p_electron_tl
+\tl_new:N \l_MOdiagram_MO_two_piys_p_electron_tl
+\tl_new:N \l_MOdiagram_MO_two_piz_p_electron_tl
+\tl_new:N \l_MOdiagram_MO_two_pizs_p_electron_tl
+
+\bool_new:N \l_MOdiagram_molecule_two_mo_p_bool
+
+\cs_new_nopar:Npn \MOdiagram_two_mo_p_set:n #1,#2;#3,#4,#5,#6,#7,#8 \q_stop
+  {
+    \bool_set_true:N \l_MOdiagram_molecule_two_mo_p_bool
+    \tl_set:Nn \l_MOdiagram_MO_two_sigma_p_electron_tl  { #3 }
+    \tl_set:Nn \l_MOdiagram_MO_two_sigmas_p_electron_tl { #8 }
+    \tl_set:Nn \l_MOdiagram_MO_two_piy_p_electron_tl    { #4 }
+    \tl_set:Nn \l_MOdiagram_MO_two_piys_p_electron_tl   { #6 }
+    \tl_set:Nn \l_MOdiagram_MO_two_piz_p_electron_tl    { #5 }
+    \tl_set:Nn \l_MOdiagram_MO_two_pizs_p_electron_tl   { #7 }
+    \dim_set:Nn \l_MOdiagram_molecule_two_psigma_dim { #1 cm }
+    \dim_set:Nn \l_MOdiagram_molecule_two_ppi_dim { #2 cm }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_two_mo_p:
+  {
+    \bool_if:NT \l_MOdiagram_molecule_two_mo_p_bool
+      {
+        \bool_if:nF
+          { \l_MOdiagram_two_p_left_bool && \l_MOdiagram_two_p_right_bool }
+          { \msg_error:nnxx { MOdiagram } { missing-AO } { 2pMO } { 2p } }
+        \MOdiagram_energy_range:n
+          {
+            \l_MOdiagram_atom_left_two_p_dim
+              - \l_MOdiagram_molecule_two_psigma_dim
+          }
+        \MOdiagram_energy_range:n
+          {
+            \l_MOdiagram_atom_right_two_p_dim
+              + \l_MOdiagram_molecule_two_psigma_dim
+          }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2psigma)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim ,
+            \l_MOdiagram_atom_left_two_p_dim
+              - \l_MOdiagram_molecule_two_psigma_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2psigma }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_sigma_p_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2psigma }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2psigma*)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim ,
+            \l_MOdiagram_atom_right_two_p_dim
+              + \l_MOdiagram_molecule_two_psigma_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2psigma* }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_sigmas_p_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2psigma* }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2piy)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim - \l_MOdiagram_AO_width_dim ,
+            \l_MOdiagram_atom_left_two_p_dim
+              - \l_MOdiagram_molecule_two_ppi_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2piy }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_piy_p_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2piy }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2piy*)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim - \l_MOdiagram_AO_width_dim ,
+            \l_MOdiagram_atom_right_two_p_dim
+              + \l_MOdiagram_molecule_two_ppi_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2piy* }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_piys_p_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2piy* }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2piz)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim + \l_MOdiagram_AO_width_dim ,
+            \l_MOdiagram_atom_left_two_p_dim
+              - \l_MOdiagram_molecule_two_ppi_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2piz }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_piz_p_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2piz }
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          (2piz*)
+          at
+          (
+            \l_MOdiagram_molecule_position_dim + \l_MOdiagram_AO_width_dim ,
+            \l_MOdiagram_atom_right_two_p_dim
+              + \l_MOdiagram_molecule_two_ppi_dim
+          )
+          {
+            \MOdiagram_get_electron_color:n { 2piz* }
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_MO_two_pizs_p_electron_tl }
+              { \tl_use:N \l_tmpb_tl }
+          } ;
+        \MOdiagram_get_orbital_label:n { 2piz* }
+        \MOdiagram_draw:f
+          { \l_MOdiagram_lines_tl }
+          (2pz left.east)  -- (2psigma.west)  (2psigma.east)   -- (2px right.west)
+          (2pz left.east)  -- (2psigma*.west) (2psigma*.east)  -- (2px right.west)
+          (2pz left.east)  -- (2piy.west)     (2piz.east)      -- (2px right.west)
+          (2pz left.east)  -- (2piy*.west)    (2piz*.east)     -- (2px right.west) ;
+      }
+  }
+
+% --------------------------------------------------------------------------- %
+% draw actual AO / MO
+\tl_new:N \l_MOdiagram_electron_color_tl
+
+\cs_new_nopar:Npn \MOdiagram_AO:nn #1#2
+  {
+    \group_begin:
+      \tl_set:Nn \l_MOdiagram_electron_color_tl { #2 }
+      \tikzpicture
+        \bool_if:NT \l_MOdiagram_AO_fancy_bool
+          {
+            \draw (0,0) -- ++(-.5*\l_MOdiagram_AO_width_dim,0) ;
+            \draw (2pt+\l_MOdiagram_AO_width_dim,0)
+                  -- ++(.5*\l_MOdiagram_AO_width_dim,0) ;
+          }
+        \MOdiagram_node:x
+          {
+            inner~sep = 0 ,
+            \bool_if:NT \l_MOdiagram_AO_square_bool { draw } ,
+            minimum~size =
+              \bool_if:NTF \l_MOdiagram_AO_square_bool
+                { 2pt+\l_MOdiagram_AO_width_dim } { 0 } ,
+            \bool_if:NT \l_MOdiagram_AO_round_bool
+              { rounded~corners=2pt }
+          }
+          at (.5*\l_MOdiagram_AO_width_dim+1pt,0)
+          {
+            \tikz
+              {
+                \bool_if:NF \l_MOdiagram_AO_square_bool
+                  { \draw (0,0) -- ++(\l_MOdiagram_AO_width_dim,0) ; }
+                \tl_set:Nn \l_tmpa_tl { #1 }
+                \tl_remove_all:Nn \l_tmpa_tl { ~ }
+                \prg_case_str:onn { \l_tmpa_tl }
+                  {
+                    { up }
+                      {
+                        \MOdiagram_draw:f
+                          { -left~to,semithick , \l_MOdiagram_electron_color_tl }
+                          (.4*\l_MOdiagram_AO_width_dim,-.4*\l_MOdiagram_AO_width_dim)
+                          -- ++(0,.8*\l_MOdiagram_AO_width_dim) ;
+                      }
+                    { down }
+                      {
+                        \MOdiagram_draw:f
+                          { -left~to,semithick , \l_MOdiagram_electron_color_tl }
+                          (.6*\l_MOdiagram_AO_width_dim,.4*\l_MOdiagram_AO_width_dim)
+                          -- ++(0,-.8*\l_MOdiagram_AO_width_dim) ;
+                      }
+                    { pair }
+                      {
+                        \MOdiagram_draw:f
+                          { -left~to,semithick , \l_MOdiagram_electron_color_tl }
+                          (.4*\l_MOdiagram_AO_width_dim,-.4*\l_MOdiagram_AO_width_dim)
+                          -- ++(0,.8*\l_MOdiagram_AO_width_dim) ;
+                        \MOdiagram_draw:f
+                          { -left~to,semithick , \l_MOdiagram_electron_color_tl }
+                          (.6*\l_MOdiagram_AO_width_dim,.4*\l_MOdiagram_AO_width_dim)
+                          -- ++(0,-.8*\l_MOdiagram_AO_width_dim) ;
+                      }
+                  }
+                  {}
+              }
+          } ;
+      \endtikzpicture
+    \group_end:
+  }
+\cs_generate_variant:Nn \MOdiagram_AO:nn { ff }
+
+% -------------------------------------------------------------------------- %
+% per default disable all AOs / MOs
+\cs_new_nopar:Npn \MOdiagram_atom_disable:
+  {
+    \bool_set_false:N \l_MOdiagram_atom_one_s_bool
+    \bool_set_false:N \l_MOdiagram_atom_two_s_bool
+    \bool_set_false:N \l_MOdiagram_atom_two_p_bool
+%     \bool_set_false:N \l_MOdiagram_atom_three_s_bool
+%     \bool_set_false:N \l_MOdiagram_atom_three_p_bool
+  }
+
+\cs_new_nopar:Npn \MOdiagram_molecule_disable:
+  {
+    \bool_set_false:N \l_MOdiagram_molecule_one_mo_s_bool
+  }
+
+% --------------------------------------------------------------------------- %
+% arbitrary placement of AOs / MOs
+\dim_new:N \l_MOdiagram_AO_dim % y
+\dim_new:N \l_MOdiagram_AO_position_dim % x
+
+\dim_new:N \l_MOdiagram_AO_px_shift_dim
+\dim_new:N \l_MOdiagram_AO_py_shift_dim
+\dim_new:N \l_MOdiagram_AO_pz_shift_dim
+
+\tl_new:N \l_MOdiagram_AO_px_electron_tl
+\tl_new:N \l_MOdiagram_AO_py_electron_tl
+\tl_new:N \l_MOdiagram_AO_pz_electron_tl
+
+\tl_new:N \l_MOdiagram_AO_name_tl
+
+\bool_new:N \l_MOdiagram_AO_p_bool
+\bool_new:N \l_MOdiagram_AO_left_bool
+
+\cs_new_nopar:Npn \MOdiagram_AO_s_set:n #1;#2 \q_stop
+  {
+    \dim_set:Nn \l_MOdiagram_AO_dim { #1 cm }
+    \tl_set:Nn \l_MOdiagram_AO_px_electron_tl { #2 }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_AO_p_set:n #1;#2,#3,#4 \q_stop
+  {
+    \dim_set:Nn \l_MOdiagram_AO_dim { #1 cm }
+    \tl_set:Nn \l_MOdiagram_AO_px_electron_tl { #2 }
+    \tl_set:Nn \l_MOdiagram_AO_py_electron_tl { #3 }
+    \tl_set:Nn \l_MOdiagram_AO_pz_electron_tl { #4 }
+  }
+
+\keys_define:nn { MOdiagram / AO }
+  {
+    type     .choice: ,
+    type / s .code:n = { \bool_set_false:N \l_MOdiagram_AO_p_bool } ,
+    type / p .code:n = { \bool_set_true:N \l_MOdiagram_AO_p_bool }
+  }
+
+% AO[<name>](<x-coord>){<type>}{<AO-spec>}
+\NewDocumentCommand \AO { o D(){0cm} m m }
+  {
+    \IfNoValueF { #1 } { \tl_set:Nn \l_MOdiagram_AO_name_tl { #1 } }
+    \keys_set:nn { MOdiagram / AO } { type = #3 }
+    \bool_if:NTF \l_MOdiagram_AO_p_bool
+      { \MOdiagram_AO_p_set:n #4 \q_stop }
+      { \MOdiagram_AO_s_set:n #4 \q_stop }
+    \dim_set:Nn \l_MOdiagram_AO_position_dim { #2 }
+%     \fp_set_from_dim:Nn \l_tmpa_tl { \l_MOdiagram_AO_width_dim }
+    \MOdiagram_p_orbitals_shift:nnn { 0 } { 2 } { 4 }
+    \MOdiagram_energy_range:N \l_MOdiagram_AO_dim
+    \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+      (
+        \tl_use:N \l_MOdiagram_AO_name_tl
+        \bool_if:NT \l_MOdiagram_AO_p_bool { x }
+      )
+      at
+      (
+        \l_MOdiagram_AO_position_dim + \l_MOdiagram_atom_px_shift_dim ,
+        \l_MOdiagram_AO_dim
+      )
+      {
+        \MOdiagram_AO:ff
+          { \tl_use:N \l_MOdiagram_AO_px_electron_tl }
+          {  }
+      } ;
+    % TODO get & set label
+    \bool_if:NT \l_MOdiagram_AO_p_bool
+      {
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          ( \tl_use:N \l_MOdiagram_AO_name_tl y )
+          at
+          (
+            \l_MOdiagram_AO_position_dim + \l_MOdiagram_atom_py_shift_dim ,
+            \l_MOdiagram_AO_dim
+          )
+          {
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_AO_py_electron_tl }
+              {  }
+          } ;
+        % TODO get & set label
+        \MOdiagram_node:n { inner~sep=0 , outer~sep=0 }
+          ( \tl_use:N \l_MOdiagram_AO_name_tl z )
+          at
+          (
+            \l_MOdiagram_AO_position_dim + \l_MOdiagram_atom_pz_shift_dim ,
+            \l_MOdiagram_AO_dim
+          )
+          {
+            \MOdiagram_AO:ff
+              { \tl_use:N \l_MOdiagram_AO_pz_electron_tl }
+              {  }
+          } ;
+        % TODO get & set label
+      }
+  }
+
+% --------------------------------------------------------------------------- %
+\NewDocumentCommand \AOinline { o m }
+  {
+    \group_begin:
+      \IfNoValueTF { #1 }
+        { ~ \MOsetup { style=square,AO-width=8pt } }
+        { ~ \MOsetup { style=square,AO-width=8pt , #1 } }
+      \begin{MOdiagram}
+        \AO{s}{0;#2}
+      \end{MOdiagram}
+    \group_end:
+  } 
+
+% --------------------------------------------------------------------------- %
+% connect arbitrary AOs / MOs
+\NewDocumentCommand \connect { m }
+  {
+    \clist_map_variable:nNn { #1 } \l_tmpa_tl
+      {
+        \tl_remove_all:Nn \l_tmpa_tl { ~ }
+        \tl_if_blank:VF \l_tmpa_tl
+          {
+            \MOdiagram_detect_nodes:x { \l_tmpa_tl }
+             \tl_if_in:NnF \l_MOdiagram_node_A_tl { . }
+               { \tl_put_right:Nn \l_MOdiagram_node_A_tl { . east } }
+             \tl_if_in:NnF \l_MOdiagram_node_B_tl { . }
+               { \tl_put_right:Nn \l_MOdiagram_node_B_tl { . west } }
+            \MOdiagram_draw_connection:xxx
+              { \tl_use:N \l_MOdiagram_lines_tl }
+              { \tl_use:N \l_MOdiagram_node_A_tl }
+              { \tl_use:N \l_MOdiagram_node_B_tl }
+          }
+      }
+  }
+
+\NewDocumentCommand \MOdiagram_detect_nodes:n { > { \SplitArgument { 1 } { & } } m }
+  { \MOdiagram_detect_nodes_aux_i:nn #1 }
+\cs_generate_variant:Nn \MOdiagram_detect_nodes:n { x }
+
+\cs_new_nopar:Npn \MOdiagram_detect_nodes_aux_i:nn #1#2
+  {
+    \tl_set:Nn \l_MOdiagram_node_A_tl { #1 }
+    \tl_set:Nn \l_MOdiagram_node_B_tl { #2 }
+  }
+
+\cs_new_nopar:Npn \MOdiagram_draw_connection:nnn #1#2#3
+  { \draw[#1] (#2) -- (#3) ; }
+\cs_generate_variant:Nn \MOdiagram_draw_connection:nnn { xxx }
+
+% --------------------------------------------------------------------------- %
+% orbital labels
+\prop_new:N \l_MOdiagram_orbital_label_prop
+\tl_set:Nn \l_MOdiagram_orbital_label_fontsize_tl { \small }
+
+\cs_new_nopar:Npn \MOdiagram_orbital_label_set:n #1
+  { \keys_set:nn { MOdiagram / label } { #1 } }
+
+\cs_new_nopar:Npn \MOdiagram_get_orbital_label:n #1
+  {
+    \tl_clear:N \l_tmpa_tl
+    \tl_clear:N \l_tmpb_tl
+    \prop_get:NnNT \l_MOdiagram_orbital_label_prop { #1 } \l_tmpa_tl
+      {
+        \MOdiagram_node:x
+          { below , \tl_use:N \l_MOdiagram_orbital_label_style_tl }
+          at ( #1 . south )
+          {
+            \tl_use:N \l_MOdiagram_orbital_label_fontsize_tl
+            \tl_use:N \l_tmpa_tl
+          } ;
+      }
+  }
+
+\keys_define:nn { MOdiagram / label }
+  {
+    1sleft   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sleft }   { #1 } } ,
+    1sright  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sright }  { #1 } } ,
+    2sleft   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sleft }   { #1 } } ,
+    2sright  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sright }  { #1 } } ,
+    2pxleft  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pxleft }  { #1 } } ,
+    2pxright .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pxright } { #1 } } ,
+    2pyleft  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pyleft }  { #1 } } ,
+    2pyright .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pyright } { #1 } } ,
+    2pzleft  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pzleft }  { #1 } } ,
+    2pzright .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pzright } { #1 } } ,
+    1sigma   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sigma }   { #1 } } ,
+    1sigma*  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sigma* }  { #1 } } ,
+    2sigma   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sigma }   { #1 } } ,
+    2sigma*  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sigma* }  { #1 } } ,
+    2psigma  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2psigma }  { #1 } } ,
+    2psigma* .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2psigma* } { #1 } } ,
+    2piy     .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piy }     { #1 } } ,
+    2piy*    .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piy* }    { #1 } } ,
+    2piz     .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piz }     { #1 } } ,
+    2piz*    .code:n =
+      { \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piz* }    { #1 } }
+  }
+
+\char_set_catcode_math_subscript:N \@
+\cs_new_nopar:Npn \MOdiagram_set_labels:
+  {
+    \bool_if:NT \l_MOdiagram_AO_labels_bool
+      {
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sleft }   { 1s }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sright }  { 1s }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sleft }   { 2s }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sright }  { 2s }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pxleft }  { 2p$@x$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pxright } { 2p$@x$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pyleft }  { 2p$@y$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pyright } { 2p$@y$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pzleft }  { 2p$@z$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2pzright } { 2p$@z$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sigma }   { 1\textsigma$@s$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 1sigma* }  { 1\textsigma$^*@s$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sigma }   { 2\textsigma$@s$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2sigma* }  { 2\textsigma$^*@s$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2psigma }  { 2\textsigma$@x$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2psigma* } { 2\textsigma$^*@x$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piy }     { 2\textpi$@y$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piy* }    { 2\textpi$^*@y$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piz }     { 2\textpi$@z$ }
+        \prop_put:Nnn \l_MOdiagram_orbital_label_prop { 2piz* }    { 2\textpi$^*@z$ }
+      }
+  }
+\char_set_catcode_letter:N \@
+
+% --------------------------------------------------------------------------- %
+% electron colours
+\prop_new:N \l_MOdiagram_electron_color_prop
+
+\cs_new_nopar:Npn \MOdiagram_electron_color_set:n #1
+  { \keys_set:nn { MOdiagram / color } { #1 } }
+
+\cs_new_nopar:Npn \MOdiagram_get_electron_color:n #1
+  {
+    \tl_clear:N \l_tmpa_tl
+    \tl_clear:N \l_tmpb_tl
+    \prop_get:NnNT \l_MOdiagram_electron_color_prop { #1 } \l_tmpa_tl
+      { \tl_set_eq:NN \l_tmpb_tl \l_tmpa_tl }
+  }
+
+\keys_define:nn { MOdiagram / color }
+  {
+    1sleft   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 1sleft }   { #1 } } ,
+    1sright  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 1sright }  { #1 } } ,
+    2sleft   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2sleft }   { #1 } } ,
+    2sright  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2sright }  { #1 } } ,
+    2pxleft  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2pxleft }  { #1 } } ,
+    2pxright .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2pxright } { #1 } } ,
+    2pyleft  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2pyleft }  { #1 } } ,
+    2pyright .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2pyright } { #1 } } ,
+    2pzleft  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2pzleft }  { #1 } } ,
+    2pzright .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2pzright } { #1 } } ,
+    1sigma   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 1sigma }   { #1 } } ,
+    1sigma*  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 1sigma* }  { #1 } } ,
+    2sigma   .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2sigma }   { #1 } } ,
+    2sigma*  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2sigma* }  { #1 } } ,
+    2psigma  .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2psigma }  { #1 } } ,
+    2psigma* .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2psigma* } { #1 } } ,
+    2piy     .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2piy }     { #1 } } ,
+    2piy*    .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2piy* }    { #1 } } ,
+    2piz     .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2piz }     { #1 } } ,
+    2piz*    .code:n =
+      { \prop_put:Nnn \l_MOdiagram_electron_color_prop { 2piz* }    { #1 } }
+  }
+
+% --------------------------------------------------------------------------- %
+% energy axis
+\dim_new:N \l_energy_axis_dim
+\dim_set:Nn \l_energy_axis_dim { 0pt }
+
+\tl_new:N \l_MOdiagram_Eaxis_head_tl
+\tl_set:Nn \l_MOdiagram_Eaxis_head_tl { latex }
+\tl_new:N \l_MOdiagram_Eaxis_title_tl
+
+\bool_new:N \l_MOdiagram_Eaxis_title_bool
+\bool_set_false:N \l_MOdiagram_Eaxis_title_bool
+
+\NewDocumentCommand \EnergyAxis { o }
+  {
+    \IfNoValueF { #1 } { \keys_set:nn { MOdiagram / axis } { #1 } }
+    \MOdiagram_draw:f { - \tl_use:N \l_MOdiagram_Eaxis_head_tl }
+      (\l_energy_axis_dim , \g_MOdiagram_min_energy_dim - 1cm )
+      --
+      (\l_energy_axis_dim , \g_MOdiagram_max_energy_dim + 1cm ) 
+      \bool_if:NT \l_MOdiagram_Eaxis_title_bool
+        { node [ above ] { \tl_use:N \l_MOdiagram_Eaxis_title_tl } }
+    ;
+  }
+
+\keys_define:nn { MOdiagram / axis }
+  {
+    title .code:n =
+      {
+        \bool_set_true:N \l_MOdiagram_Eaxis_title_bool
+        \tl_set:Nn \l_MOdiagram_Eaxis_title_tl { #1 }
+      } ,
+    title .default:n = energy ,
+    head  .tl_set:N  = \l_MOdiagram_Eaxis_head_tl ,
+    head  .default:n = >
+  }
+
+% --------------------------------------------------------------------------- %
+% tikz helper functions
+\cs_new_nopar:Npn \MOdiagram_node:n #1
+  { \node [ #1 ] }
+\cs_generate_variant:Nn \MOdiagram_node:n { f,x }
+
+\cs_new_nopar:Npn \MOdiagram_draw:n #1
+  { \draw [ #1 ] }
+\cs_generate_variant:Nn \MOdiagram_draw:n { f }
+
+\cs_new_nopar:Npn \MOdiagram_tikz:nn #1
+  { \tikz [ #1 ] }
+\cs_generate_variant:Nn \MOdiagram_tikz:nn { fn,xn }
+
+\cs_new_nopar:Npn \MOdiagram_tikzpicture:n #1
+  { \tikzpicture [ #1 ] }
+\cs_generate_variant:Nn \MOdiagram_tikzpicture:n { f }
+
+\tex_endinput:D
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+Version history
+2011/09/25 version 0.1 - first upload to CTAN
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% TODO
+- 3s, 3p , 3sMO , 3pMO , 4s , sp3
+- Farbe und Label der \AO setzen können
+- key shift analog zu color und label, mit dem eine horizontale Verschiebung
+  der el möglich ist.
+- energy axis: ticks? at orbital heights?
\ No newline at end of file
diff --git a/Master/tlpkg/bin/tlpkg-ctan-check b/Master/tlpkg/bin/tlpkg-ctan-check
index 9104ee851ae..09c02fb313a 100755
--- a/Master/tlpkg/bin/tlpkg-ctan-check
+++ b/Master/tlpkg/bin/tlpkg-ctan-check
@@ -254,7 +254,7 @@ my @TLP_working = qw(
     minted minutes
     mkgrkindex mkjobtexmf mkpattern
     mla-paper mlist mmap mnsymbol
-    moderncv modref modroman mongolian-babel montex
+    moderncv modiagram modref modroman mongolian-babel montex
     moreenum morefloats morehype moresize
     moreverb morewrites movie15 mp3d mparhack mpcolornames mpgraphics
     mpman-ru ms msc msg mslapa msu-thesis mtgreek
diff --git a/Master/tlpkg/tlpsrc/collection-pictures.tlpsrc b/Master/tlpkg/tlpsrc/collection-pictures.tlpsrc
index 40c5a6d0ac3..ae9424185cf 100644
--- a/Master/tlpkg/tlpsrc/collection-pictures.tlpsrc
+++ b/Master/tlpkg/tlpsrc/collection-pictures.tlpsrc
@@ -40,6 +40,7 @@ depend lapdf
 depend lpic
 depend mathspic
 depend miniplot
+depend modiagram
 depend numericplots
 depend pb-diagram
 depend petri-nets
diff --git a/Master/tlpkg/tlpsrc/modiagram.tlpsrc b/Master/tlpkg/tlpsrc/modiagram.tlpsrc
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/Master/tlpkg/tlpsrc/modiagram.tlpsrc