[Tex/LaTex] Molecular orbital diagram for CH2

modiagramtikz-pgf

I'm trying to draw an MO diagram for CH2 by mimicking this MO diagram (excluding the orbital images), but things don't look like the way I want it to be. I really want to make it nice and similar to the image, but what I'm doing right now just seems sad and would really appreciate it if someone can help me.

enter image description here

I tried using MOdiagram package, but needs A LOT of work on it, especially with the overall size of the diagram because it is too small when I typeset. So, it would be really nice if someone can help me. Please and thank you. 

\documentclass{article}
\usepackage{modiagram}
\usepackage[version=4]{mhchem}
\begin{document}

\begin{MOdiagram}[labels-fs=\scriptsize]
        \AO(1cm){s}[label={2s}]{0.5;}
        \AO(-0.4cm){p}[label={2p}]{2;}
        \node at (1cm, -1){C};
        %%%%%%%%%%%%%%%%%%%%%%%
        \AO(3cm){s}[label={$2\mathrm{a}_1$}]{0;pair}
        \AO(3cm){s}[label={1e}]{0.9;pair} 
        \AO(3cm){s}{1.1;pair} 
        \AO(3cm){s}[label={$3\mathrm{a}_1$}]{2;pair}
        \AO(3cm){s}[label={$4\mathrm{a}_1$}]{3;}
        \AO(3cm){s}[label={2e}]{3.9;}
        \AO(3cm){s}{4.1;}
        \node at (3cm, -1){\ce{CH_2}};
        %%%%%%%%%%%%%%%%%%%%%%%
        \AO(5cm){s}[label={1s}]{2.5;}
        \node at (5cm, -1){H};
\end{MOdiagram}


\end{document}

Best Answer

I haven't used MOdiagram before, but as you tagged the question , here is a (simple) pure TikZ solution.

I am not even using a chemistry package and writing BeH2 as BeH$_2$ :) but you really should change that in your document.

\documentclass[tikz,margin=3mm]{standalone}
\begin{document}
\begin{tikzpicture}
\draw[dotted] (-3,0)--(-.3,3)--(.3,3)--(4,-1)--(.3,-4.5)--(-.3,-4.5)--cycle;
\draw[dotted] (-3,-1.5)--(-.3,1.5)--(.3,1.5)--(4,-2)--(.3,-6.5)--(-.3,-6.5)--cycle;
\draw[thick] (-.3,3)--(.3,3) (-.3,1.5)--(.3,1.5) (-.8,0)--(-.2,0) (.2,0)--(.8,0) (-.3,-4.5)--(.3,-4.5) (-.3,-6.5)--(.3,-6.5) (-3,0)--(-3.6,0) node[midway,below] {$2p_z$} (-3.8,0)--(-4.4,0) node[midway,below] {$2p_y$} (-4.6,0)--(-5.2,0) node[midway,below] {$2p_x$} (-3,-1.5)--(-3.6,-1.5) node[midway,below] {$2s$} (4,-2)--(4.6,-2) node[midway,below] {$\Phi_\mathrm g$} (4,-1)--(4.6,-1) node[midway,below] {$\Phi_\mathrm u$};
\draw[dotted] (-4.6,0)--(1.9,0);
\draw (0,0) node[below] {$\pi_\mathrm u^\mathrm n$};
\draw (0,.75) node {$\sigma^*_\mathrm g$};
\draw (0,2.25) node {$\sigma^*_\mathrm u$};
\draw (0,-5.5) node {$\sigma_\mathrm u$};
\draw (0,-4.5) node {\rotatebox{90}{$\rightleftharpoons$}};
\draw (0,-6.5) node {\rotatebox{90}{$\rightleftharpoons$}};
\draw (0,-7) node {$\sigma_\mathrm g$};
\draw (-4.2,4) node {Be};
\draw (0,4) node {BeH$_2$};
\draw (4.2,4) node {2 H (\textsc{salc}s)};
\end{tikzpicture}
\end{document}

enter image description here

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