Real-space pseudopotential method for spin-orbit coupling within density functional theory

We present a formalism and implementation for real-space calculations that incorporate relativistic effects, including spin-orbit coupling. We demonstrate the validity of the method using the test cases of AuH and the Au-2 dimer. The proposed approach differs from nonrelativistic real-space calculations in the addition of nonlocal pseudopotential projectors, which are translated to small rank-1 matrix "stencils" operating on the discretized wave functions. This formalism retains all the usual benefits of the real-space approach, especially with respect to massive parallelization. We expect it to be readily applicable for computational studies of large systems exhibiting spin-orbit coupling effects.