Meta-GGA Performance in Solids at Almost GGA Cost

TL;DR

This paper introduces r$^2$SCAN-L, a computationally efficient meta-GGA functional for solids that maintains accuracy in various properties and improves over previous versions in speed and stability.

Contribution

The study demonstrates that deorbitalization of r$^2$SCAN to r$^2$SCAN-L retains accuracy while significantly reducing computational cost and iteration counts.

Findings

r$^2$SCAN-L is faster than r$^2$SCAN and SCAN-L.

r$^2$SCAN-L maintains accuracy in molecular and solid-state properties.

Over-magnetization in bcc Fe persists in r$^2$SCAN but not in r$^2$SCAN-L.

Abstract

A recent modification, r$^2$SCAN, of the SCAN (strongly constrained and appropriately normed) meta-GGA exchange-correlation functional mostly eliminates numerical instabilities and attendant integration grid sensitivities exhibited by SCAN. Here we show that the successful deorbitalization of SCAN to SCAN-L (SCAN with density Laplacian dependence) carries over directly to yield r$^2$SCAN-L. A major benefit is that the high iteration counts that hindered use of SCAN-L are eliminated in r$^2$SCAN-L. It therefore is a computationally much faster meta-GGA than its orbital-dependent antecedent. Validation data for molecular heats of formation, bond lengths, and vibration frequencies (G3/99X, T96-R, T82-F test sets respectively) and on lattice constants, and cohesive energies (for 55 solids) and bulk moduli (for 40 solids) are provided. In addition, we show that the over-magnetization of bcc Fe from SCAN persists in r$^2$SCAN but does not appear in r$^2$SCAN-L, just as with SCAN-L.