Optimization of kinetic energy functionals for deorbitalized exchange-correlation meta-GGAs.

Deorbitalized meta-GGA functionals for the exchange-correlation energy [1,2] have shown promise as a cost-effective alternative to conventional meta-GGAs. These replace the noninteracting kinetic energy (KE) density used in a meta-GGA with a pure functional of the density. The Perdew-Constantin and related KE functionals (Phys. Rev. B 75, 155109 (2007)) use the Laplacian of the density to switch from the slowly varying electron gas to the localized electron-pair limits, resulting in an accurate orbital-free model for the KE density. However, use of the density Laplacian can create unphysical Pauli and exchange-correlation potentials that are numerically slow to converge and lead to noisy results. We construct a measure of the noisiness of functional potentials and discuss an optimization procedure for minimizing fluctuations in the potential based on the Poisson equation, used to generate modifications of the PC and related functionals. We find that modifications of the RPP KE functional [2] show particular promise for efficient use in meta-GGAs as measured by number of self-consistent cycles and time-per-cycle.

[1] D. Mejia-Rodriguez and S. B. Trickey Phys. Rev. A 96, 052512 (2017)

[2] A Kaplan and J Perdew Phys. Rev. Materials 6, 083803 (2022)