MOPAC

In computational chemistry, MOPAC is a popular computer program designed to implement semi-empirical quantum chemistry algorithms, such as MINDO, MNDO, AM1, PM3, PM5, Sparkle/AM1, Sparkle/PM3 and RM1. Its name is derived from Molecular Orbital PACkage. It was largely written in the group of Michael Dewar.

The latest versions are no longer public domain software as were the earlier versions such as MOPAC6 and MOPAC7. However, there are recent efforts to keep MOPAC7 working as open source software. An open source version of MOPAC7 for linux is also available. The author of MOPAC, James Stewart, released in 2006 a public domain version of MOPAC7 entirely written in Fortran 90 called MOPAC7.1.

In 2007 James Stewart released MOPAC2007, which is free for academics.

MOPAC2007 includes the new Sparkle/AM1, Sparkle/PM3, RM1 and PM6 models, with an increased emphasis on solid state capabilities. However it does not have yet MINDO/3, PM5, analytical derivatives, the Tomasi solvation model and intersystem crossing.

MOPAC2007 is available for both Windows and Linux operating systems.