Analytic Spin-Orbit Coupling Matrix Element Formulae in FLAPW Calculations

The full-potential, linearized augmented, plane wave (FLAPW) method is used widely for accurate electronic structure calculations. For the electronic structure of solids with heavy elements, it is necessary to include spin-orbit coupling interactions. We present simple analytic formulae for calculating FLAPW spin-orbit matrix elements. These will serve to simplify the calculations and save computational time.