{modiagram} is for questions specifically related to the creation of Molecular Orbital diagrams in LaTeX, using the modiagram package.
modiagram is a package that provides the environment MOdiagram and some commands, to create molecular orbital diagrams using TikZ.
For example, the MO diagram of dihydrogen would be written as:
\begin{MOdiagram}
\atom{left}{ 1s = {0;up} }
\atom{right}{ 1s = {0;up} }
\molecule{ 1sMO = {1;pair, } }
\end{MOdiagram}