From Incomplete Allowance for Electron Correlation to the Full CI in π-Systems. The Variational Operator Approach

Abstract

Electron correlation in the real physical systems may be investigated in many sophisticated ways and means, and from among them one ought to prefer such a general approach that leads to approximate but reliable consideration as well as to the exact one. Therefore, when describing the electronic structure of molecular systems we favour the most extended modus operandi which is supplied us by the operator algebra. An important advantage of the study in terms of the operators is its ability to set up the electronic model in invariant (more precisely, covariant) terms. It means, the main equations have the same form no matter how the orbital frame is constructed.