Lattice dynamics and structural phase stability of group-IV elemental solids with the r2SCAN functional

The strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation (metaGGA) functional is a milestone achievement of electronic structure theory. Recently, a revised and restored form (r2SCAN) has been suggested as a replacement for SCAN in high-throughput applications. Here, we assess the accuracy and reliability of the r2SCAN meta-GGA functional for the group-IV elemental solids carbon (C), silicon (Si), germanium (Ge), and tin (Sn). We show that the r2SCAN functional agrees closely with its parent functional SCAN for elastic constants, bulk moduli, and phonon dispersions, but the numerical stability of r2SCAN is superior. Both meta-GGA functionals outperform standard GGA (Perdew-Burke-Ernzerhof) in terms of accuracy and approach the level of common hybrid functionals (Heyd-Scuseria-Ernzerhof). However, we find that r2SCAN performs much worse than SCAN for the α ↔ β phase transition of both Ge and Sn, yielding larger phase energy differences and transition pressures.