Orthogonalized linear combinations of atomic orbitals. IV. Inclusion of relativistic corrections

The relativistic corrections to the band-structure calculation have been implemented in the orthogonalized linear combinations of atomic orbitals method. A two-step process is suggested such that the scalar-relativistic effects due to the spin-independent mass-velocity and Darwin terms are treated first. Spin-orbit interaction is then included on the basis of the spin-polarized band structures. All other higher-order corrections are ignored. Test calculations on scalar-relativistic corrections are demonstrated in the elemental methods Ni, Nb, and Ce with increasing atomic mass numbers. The results are in very good agreement with the established results using other band methods. The full relativistic band structure is calculated for ferromagnetic Fe. It is shown that the effect of spin-orbit interaction in Fe is of considerable importance compared with the scalar-relativistic correction.