r2SCAN-D4: Dispersion corrected meta-generalized gradient approximation for general chemical applications

TL;DR

r2SCAN-D4 is a new density functional combining a regularized meta-GGA with dispersion correction, achieving hybrid-like accuracy in chemical applications while maintaining GGA-level speed, demonstrated across diverse molecular and condensed systems.

Contribution

It introduces r2SCAN-D4, a dispersion-corrected meta-GGA functional that offers hybrid accuracy with GGA speed for broad chemical applications.

Findings

Errors of 0.8% in bond lengths for main group and transition metals.

WTMAD2 of 7.5 kcal/mol on GMTKN55 database.

Lattice energies of molecular crystals within 1 kcal/mol accuracy.

Abstract

We combine a regularized variant of the strongly constrained and appropriately normed semilocal density functional [J. Sun, A. Ruzsinszky, and J. P. Perdew, Phys. Rev. Lett. 115, 036402 (2015)] with the latest generation semi-classical London dispersion correction. The resulting density functional approximation r2SCAN-D4 has the speed of generalized gradient approximations while approaching the accuracy of hybrid functionals for general chemical applications. We demonstrate its numerical robustness in real-life settings and benchmark molecular geometries, general main group and organo-metallic thermochemistry, as well as non-covalent interactions in supramolecular complexes and molecular crystals. Main group and transition metal bond lengths have errors of just 0.8%, which is competitive with hybrid functionals for main group molecules and outperforms them for transition metal complexes. The weighted mean absolute deviation (WTMAD2) on the large GMTKN55 database of chemical properties is exceptionally small at 7.5 kcal/mol. This also holds for metal organic reactions with an MAD of 3.3 kcal/mol. The versatile applicability to organic and metal-organic systems transfers to condensed systems, where lattice energies of molecular crystals are within chemical accuracy (errors <1 kcal/mol).