Cw. Bauschlicher et H. Partridge, ON THE INVARIANCE OF THE CONFIGURATION-INTERACTION ENERGY WITH RESPECT TO ORBITAL ROTATIONS, Theoretica Chimica Acta, 85(4), 1993, pp. 255-259
The invariance of the configuration interaction (CI) energy with respe
ct to orbital rotation is considered. The inclusion of all spin coupli
ngs versus only those from the first-order interacting space is consid
ered. A definition for the analog of a second-order CI calculation whe
n inactive electrons are present is proposed.