Capturing static and dynamic correlations by a combination of projected Hartree-Fock and density functional theories

摘要

This paper explores the possibility of combining projected Hartree-Fock and density functional theoriesfor treating static and dynamic correlations in molecular systems with mean-field computationalcost. The combination of spin-projected unrestricted Hartree-Fock (SUHF) with the TPSS correlationfunctional (SUHF+TPSS) yields excellent results for non-metallic molecular dissociations andsinglet-triplet splittings. However, SUHF+TPSS fails to provide the qualitatively correct dissociationcurve for the notoriously difficult case of the chromium dimer. By tuning the TPSS correlation parametersand adding complex conjugation symmetry breaking and restoration to SUHF, the right curveshape for Cr2 can be obtained; unfortunately, such a combination is found to lead to overcorrelationin the general case.