Multireference density functional theory with orbital‐dependent correlation corrections

Abstract

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. Int J Quantum Chem, 2006