Does GLPT2 Offer Any Actual Benefit Over Conventional HF-MP2 In the Context of Double-Hybrid Density Functionals?

TL;DR

This study evaluates whether using Kohn-Sham orbitals in double-hybrid density functionals offers significant advantages over Hartree-Fock orbitals, finding that KS orbitals are beneficial but with limited added value.

Contribution

The paper provides a comprehensive comparison of KS and HF orbitals in double-hybrid functionals using the GMTKN55 dataset, clarifying their relative benefits.

Findings

KS orbitals offer benefits over HF orbitals in double-hybrid functionals.

The advantage of KS orbitals is present but not as substantial as expected.

Results are based on a large, diverse chemical dataset.

Abstract

While the inclusion of the nonlocal correlation in fifth rung "double hybrid" functionals is definitely beneficial, one might rightfully ask whether its evaluation in the basis of Kohn-Sham (KS) orbitals has additional value compared to the use of Hartree-Fock reference orbitals (in a type of multilevel scheme). We have investigated this question for a very large and chemically diverse dataset, GMTKN55. We conclude that KS reference orbitals are undoubtedly beneficial, but the benefit is not as large as one might intuitively expect.