A mixed ultrasoft/normconserved pseudopotential scheme

TL;DR

This paper introduces a modified ultrasoft pseudopotential scheme that relaxes norm conservation for specific channels, improving computational efficiency and accuracy for transition metals like rhodium.

Contribution

It presents a novel mixed ultrasoft/normconserved pseudopotential scheme that overcomes key limitations of traditional ultrasoft pseudopotentials without losing their advantages.

Findings

Ghost states are avoided without semicore shells

Pseudo-charge-augmentation functions are more flexible

Reduced number of nonlocal operators

Abstract

A variant of the Vanderbilt ultrasoft pseudopotential scheme, where the normconservation is released for only one or a few angular channels, is presented. Within this scheme some difficulties of the truly ultrasoft pseudopotentials are overcome without sacrificing the pseudopotential softness. i) Ghost states are easily avoided without including semicore shells. ii) The ultrasoft pseudo-charge-augmentation functions can be made more soft. iii) The number of nonlocal operators is reduced. The scheme will be most useful for transition metals, and the feasibility and accuracy of the scheme is demonstrated for the 4d transition metal rhodium.