  The Strongly Constrained and Appropriately Normed (SCAN) functional is a
non-empirical meta-generalized-gradient approximation (meta-GGA) functional
that satisfies all the known constraints that a meta-GGA functional can, but it
also exhibits a great degree of sensitivity to numerical grids. Its numerical
complexities are amplified when used in Perdew-Zunger (PZ) self-interaction
correction (SIC) which requires evaluating energies and potentials using
orbital densities that vary far more rapidly than spin densities. Recent
regularization of the SCAN functional (rSCAN) simplifies numerical complexities
of SCAN at the expense of violation of some exact constraints. To develop a
good understanding of the performance of rSCAN and the effect of loss of an
exact constraint at the limit of slowly varying density, we have compared its
performance against SCAN for vibrational frequencies, infra-red and Raman
intensities of water clusters, electric dipole moments, spin magnetic moments
of a few molecular magnets, weak interaction energies of dimers, barrier
heights of reactions, and atomization energies for benchmark sets of molecules.
Likewise, we examined the performance of SIC-rSCAN using the PZ-SIC method by
studying atomic total energies, ionization potentials and electron affinities,
molecular atomization energies, barrier heights, and dissociation and reaction
energies. We find that rSCAN requires a much less dense numerical grid and
gives very similar results as SCAN for all properties examined with the
exception of atomization energies which are somewhat worse in rSCAN. On the
other hand, SIC-rSCAN gives marginally better performance than SIC-SCAN for
almost all properties studied in this work.
