\documentclass{standalone}
\usepackage{tikz}
\usepackage{dimer_example}

\begin{document}
\hfil\begin{tikzpicture}
\basegraph

\draw[line width=3pt](A2)--(A3);
\draw[line width=3pt](A1)--(A8);
\draw[line width=3pt](D4)--(D2);
\draw[line width=3pt](C1)--(A4);
\draw[line width=3pt](B3)--(A6);
\draw[line width=3pt](A7)--(B1);

\end{tikzpicture}

\end{document}