On-site approximation for spin–orbit coupling in linear combination of atomic orbitalsdensity functional methods

Abstract

We propose a computational method that drastically simplifies the inclusion ofthe spin–orbit interaction in density functional theory when implemented overlocalized basis sets. Our method is based on a well-known procedure for obtainingpseudopotentials from atomic relativistic ab initio calculations and on an on-siteapproximation for the spin–orbit matrix elements. We have implemented thetechnique in the SIESTA (Soler J M et al 2002 J. Phys.: Condens. Matter 14 2745–79)code, and show that it provides accurate results for the overall band-structureand splittings of group IV and III–IV semiconductors as well as for 5d metals.