Mixed-Basis Scheme for DFT Calculations

Abstract

A combined basis consisting of core orbitals, in a special way localized valence orbitals, and orthogonalized (to core orbitals only) plane waves is introduced for variational solutions of Kohn-Sham equations. The localized orbitals represent atomic valence orbitals in the range of their radial nodes with high precision, but are smoothly compressed in their radial extension to almost not overlap from different sites. They are precisely orthogonal to all core states. The scheme combines high precision with high numerical efficiency: It converges very rapidly with respect to the number of plane waves (cut-off energy well below 10 Hartree for a mHartree accuracy) and allows for a rather simple analytical treatment of all needed matrix elements.