Molden is a package for displaying Molecular Density from the Ab Initio packages GAMESS-UK , GAMESS-US and GAUSSIAN and the Semi-Empirical packages Mopac/Ampac, it also supports a number of other programs via the Molden Format. Molden reads all the required information from the GAMESS / GAUSSIAN outputfile. Molden is capable of displaying Molecular Orbitals, the electron density and the Molecular minus Atomic density.
PyQuante is an open-source suite of programs for developing quantum chemistry methods. The program is written in the Python programming language, but has many "rate-determining" modules also written in C for speed.
A page run by the center for computational studies of electronic structure and spectroscopy of open-shell and electronically excited species. Links to educational material on quantum chemistry, a forum, and free software are found here.
W. Duch, and G. Diercksen. The Journal of Chemical Physics, 101 (4):
3018-3030(August 1994)Multi-reference form of the Davidson correction given here..
K. Irikura. volume 677 of ACS Symposium Series, chapter 22, page 402--418. American Chemical Society, Washington, (February 1998)Updated edition at CCCBDB..
D. Levin. Proceedings of MEST 2012: Electronic structure methods with applications to experimental chemistry, volume 68 of Advances in Quantum Chemistry, chapter 2, Academic Press, (2014)
K. Peterson, D. Feller, and D. Dixon. Theoretical Chemistry Accounts: Theory, Computation, and Modeling (Theoretica Chimica Acta), 131 (1):
1-20(January 2012)