Revisiting Gauge-Independent Kinetic Energy Densities in Meta-GGAs and Local Hybrid Calculations of Magnetizabilities

TL;DR

This study evaluates the accuracy of various density functionals, including local hybrid and range-separated hybrid functionals, in calculating magnetizabilities, emphasizing the importance of gauge-invariant kinetic energy densities in meta-GGAs.

Contribution

It introduces a larger selection of LH, RSLH, and scLH functionals and demonstrates their superior performance in magnetizability calculations compared to previous functionals.

Findings

LH, RSLH, and scLH functionals outperform previous functionals in accuracy.

Best two scLH functionals perform well even for multiconfigurational molecules like ozone.

New formulations of kinetic energy density improve magnetizability predictions.

Abstract

In a recent study [J. Chem. Theory Comput. 2021, 17, 1457-1468], some of us examined the accuracy of magnetizabilities calculated with density functionals representing the local density approximation (LDA), generalized gradient approximation (GGA), meta-GGA (mGGA) as well as global hybrid (GH) and range-separated (RS) hybrid functionals by assessment against accurate reference values obtained with coupled-cluster theory with singles, doubles and perturbative triples [CCSD(T)]. Our study was later extended to local-hybrid (LH) functionals by Holzer et al. [J. Chem. Theory Comput. 2021, 17, 2928-2947]; in this work, we examine a larger selection of LH functionals, also including range-separated LH (RSLH) functionals and strong-correlation LH (scLH) functionals. Holzer et al also studied the importance of the physically correct handling of the magnetic gauge dependence of the kinetic energy density $(\tau)$ in mGGA calculations by comparing the Maximoff--Scuseria formulation of $\tau$ used in our aforementioned study to the more physical current-density extension derived by Dobson. In this work, we also revisit this comparison with a larger selection of mGGA functionals. We find that the newly tested LH, RSLH and scLH functionals outperform all the functionals considered in the previous studies. The various LH functionals afford the seven lowest mean absolute errors, while also showing remarkably small standard deviations and mean errors. Most strikingly, the best two functionals are scLHs that also perform remarkably well in cases with significant multiconfigurational character such as the ozone molecule, which is traditionally excluded from the statistical error evaluation due to its large errors with common density functionals.