GAMESS
The General Atomic and Molecular Electronic Structure System (GAMESS) is a flexible ab initio electronic structure program. Its latest version can perform general valence bond, multiconfiguration self-consistent field, Möller-Plesset, coupled-cluster, and configuration interaction calculations. Geometry optimizations, vibrational frequencies, thermodynamic properties, and solution modeling are available. It performs well on open shell and excited state systems and can model relativistic effects.