Performance of the strongly constrained and appropriately normed density functional for solid-state materials

TL;DR

The SCAN density functional improves the accuracy of formation energy predictions and structural properties for solid-state materials, especially strongly-bound compounds, by satisfying known physical constraints.

Contribution

This study provides an extensive benchmark of the SCAN functional's performance on nearly a thousand crystalline compounds, highlighting its strengths and limitations.

Findings

SCAN reduces formation energy errors for strongly-bound compounds by 50%.

SCAN predicts more accurate crystal volumes and improves band gap estimates.

SCAN performs moderately worse than PBE for intermetallic compounds.

Abstract

Constructed to satisfy all known exact constraints and appropriate norms for a semilocal density functional, the strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation functional has shown early promise for accurately describing the electronic structure of molecules and solids. One open question is how well SCAN predicts the formation energy, a key quantity for describing the thermodynamic stability of solid-state compounds. To answer this question, we perform an extensive benchmark of SCAN by computing the formation energies for a diverse group of nearly one thousand crystalline compounds for which experimental values are known. Due to an enhanced exchange interaction in the covalent bonding regime, SCAN substantially decreases the formation energy errors for strongly-bound compounds, by approximately 50% to 110 meV/atom, as compared to the generalized gradient approximation of Perdew, Burke, and Ernzerhof (PBE). However, for intermetallic compounds, SCAN performs moderately worse than PBE with an increase in formation energy error of approximately 20%, stemming from SCAN's distinct behavior in the weak bonding regime. The formation energy errors can be further reduced via elemental chemical potential fitting. We find that SCAN leads to significantly more accurate predicted crystal volumes, moderately enhanced magnetism, and mildly improved band gaps as compared to PBE. Overall, SCAN represents a significant improvement in accurately describing the thermodynamics of strongly-bound compounds.