Relativistic extension of the Troullier-Martins scheme: Accurate pseudopotentials for transition-metal elements

A fully relativistic extension of the pseudopotential construction scheme by Troullier and Martins [Phys. Rev. B 43, 1993 (1991)] is presented. The resulting pseudopotentials are applied to a number of transition and noble metal compounds. For an unambiguous discussion of the relativistic contributions the convergence of the pseudopotential results with the size of the valence space is carefully investigated. Our results show that, for a fully quantitative comparison with experiment, pseudopotential calculations for transition and noble metal elements should treat the semicore s states dynamically, rather than via nonlinear core corrections. Using such a large valence space, very good agreement of the calculated spectroscopic parameters with the corresponding all-electron data is obtained. Reliable predictions seem to be possible, even for very critical systems like FeO. The relativistic corrections are found to be significant for all $3d$ transition metal compounds considered.