Deorbitalization strategies for meta-GGA exchange-correlation functionals

TL;DR

This paper investigates simplifying advanced exchange-correlation functionals in density functional theory by replacing orbital-dependent terms with approximate kinetic energy density functionals, aiming to reduce computational cost while maintaining accuracy.

Contribution

The study develops new approximate kinetic energy density functionals for deorbitalizing meta-GGA functionals, improving computational efficiency without significant loss of accuracy.

Findings

Deorbitalization with new KEDFs yields good results on molecular test sets.

Standard KEDFs are inadequate for deorbitalization in this context.

Potential applications in ab initio molecular dynamics simulations.

Abstract

We explore the simplification of widely used meta-generalized-gradient approximation (mGGA) exchange-correlation functionals to the Laplacian level of refinement by use of approximate kinetic energy density functionals (KEDFs). Such deorbitalization is motivated by the prospect of reducing computational cost while recovering a strictly Kohn-Sham local potential framework (rather than the usual generalized Kohn-Sham treatment of mGGAs). A KEDF that has been rather successful in solid simulations proves to be inadequate for deorbitalization but we produce other forms which, with parametrization to Kohn-Sham results (not experimental data) on a small training set, yield rather good results on standard molecular test sets when used to deorbitalize the meta-GGA made very simple, TPSS, and SCAN functionals. We also study the difference between high-fidelity and best-performing deorbitalizations and discuss possible implications for use in ab initio molecular dynamics simulations of complicated condensed phase systems.