Multireference density functional theory with orbital-dependent correlation corrections

Abstract

The features of ab initio wave function-driven multireference (MR)-density functional theory (DFT) approach based on the partially interacting reference system for ground and excited states are discussed from the viewpoint of a simple classification of electron correlation effects. Our previous MR-DFT approach covers (i) structure-free, and (ii) resonating-type correlations, but does not include (iii) orbital-dependent correlation effects. Indeed, the computational results of excitation energies of atoms imply that the state-dependent correlations remain if the CASCI wave functions are used for the wave function part of MR-DFT and semilocal correlation functional is used. Thus, we present an orbital-dependent residual correlation for complete active space (CAS) DFT to describe type (iii) of correlation effects. © 2006 Wiley Periodicals, Inc.