Orbital-dependent second-order scaled-opposite-spin correlation functionals in the optimized effective potential method

TL;DR

This paper evaluates and improves orbital-dependent second-order scaled-opposite-spin correlation functionals within the optimized effective potential method, highlighting a composite approach that balances accuracy and computational efficiency.

Contribution

It introduces a system-dependent scaling approach and a composite post-SCF rescaling method for enhanced accuracy in OEP correlation functionals.

Findings

Careful selection of the scaling coefficient improves accuracy.

The OEP2-SOSh method achieves high accuracy with reduced computational cost.

Size-extensive approaches are effective for scaling coefficient selection.

Abstract

The performance of correlated optimized effective potential (OEP) functionals based on the spin-resolved second-order correlation energy is analyzed. The relative importance of singly- and doubly- excited contributions as well as the effect of scaling the same- and opposite- spin components is investigated in detail comparing OEP results with Kohn-Sham (KS) quantities determined via an inversion procedure using accurate ab initio electronic densities. Special attention is dedicated in particular to the recently proposed scaled-opposite-spin OEP functional [I. Grabowski, E. Fabiano and F. Della Sala, Phys. Rev. B, 87, 075103, (2013)] which is the most advantageous from a computational point of view. We find that for high accuracy a careful, system dependent, selection of the scaling coefficient is required. We analyze several size-extensive approaches for this selection. Finally, we find that a composite approach, named OEP2-SOSh, based on a post-SCF rescaling of the correlation energy can yield high accuracy for many properties, being comparable with the most accurate OEP procedures previously reported in the literature but at substantially reduced computational effort.