The role of the reference state in long-range random phase approximation correlation

Abstract

We recently presented a combination of a short-range density functional approximation with long-range random phase approximation (RPA) correlation [B. G. Janesko, T. M. Henderson, and G. E. Scuseria, J. Chem. Phys. 130, 081105 (2009)]. Here we explore how this approximation's performance is affected by the choice of reference state, i.e., the orbitals and orbital energy differences entering the RPA energy expression. Our previous results built the reference state using a nonlocal exchange potential. Rescaling the RPA correlation energy by an empirical factor >1 gave very accurate results for a wide range of properties. We show here that reference states constructed from approximate local exchange-correlation potentials give their best results with smaller rescaling factors approximately 1. However, the tested potentials yield artifacts in some systems.