ANALYSIS OF LARGE-SCALE MULTI-CONFIGURATION SELF-CONSISTENT-FIELD WAVE-FUNCTIONS BY EXPECTATION VALUES OF LOCAL OPERATORS

We have developed a method to analyze multi-configuration self-consist ent field wave functions for open-shell systems, which may consist of a very large number of Slater determinants, by calculating their expec tation values for (local) one- and two-particle operators in a numeric ally efficient way. Although the proposed formalism is fully general a nd applies to any operators referring to a subset of arbitrary orthogo nal molecular orbitals, the local operators we use here are defined in terms of localized molecular orbitals: This choice permits to perform a chemically intuitive analysis of the local spin, population and cha rge fluctuation, also allowing to study electron correlation effects i n chemical bonding. We present some applications for ionic and covalen t systems considering four small molecules, H-2, N-2, H2O and CH4, as well as a binary transition metal complex, [Fe2S6](6-). (C) 1996 Ameri can Institute of Physics.