Ghemical is a computational chemistry software package, 

Ghemical relies on external code to provide the quantum-mechanical
calculations. Semi-empirical methods MNDO, MINDO/3, AM1 and PM3 come
from the MOPAC7 package, and are included in the source distribution.
The MPQC package (GNU GPL) is used to provide ab initio methods.

WWW: http://bioinformatics.org/ghemical/