On-site approximation for spin-orbit coupling in LCAO density functional methods

We propose a computational method that simplifies drastically the inclusion of spin-orbit interaction in density functional theory when implemented over localised atomic orbital basis sets. Our method is based on a well-known procedure for obtaining pseudopotentials from atomic relativistic ab initio calculations and on an on-site approximation for the spin-orbit matrix elements. We have implemented the technique in the SIESTA[34] code, and show that it provides accurate results for the overall band structure and splittings of group IV and III-IV semiconductors as well as for 5d metals. PACS numbers: 71.15.Ap,71.15.Dx,71.15.Rf,71.20.Be,71.20.Mq On-site Spin-orbit for LCAO 2 Submitted to: J. Phys.: Condens. Matter