The spinor COHSEX and GW calculations in KSSOLV: Implementation and benchmarking
Description
The GW method is a widely employed approach for calculating quasiparticle energies and band structures of materials. The static Coulomb hole plus screened exchange (COHSEX) approximation, which corresponds to the static limit of the GW self-energy, provides a computationally efficient alternative. In systems with spin-orbit coupling (SOC), it is conventional practice to treat SOC as a perturbation and apply GW corrections separately to obtain quasiparticle energies incorporating SOC effects. However, this approach may be inadequate for accurately describing these effects due to its initial neglect of spin degrees of freedom. To address this limitation, we implement the spinor COHSEX and GW formalism in KSSOLV, a MATLAB toolbox for electronic structure calculations using Kohn-Sham density functional theory. Our implementation enables meticulous treatment of spinor in COHSEX and GW calculations. We validate the correctness and computational efficiency of our approach by calculating quasiparticle energies for various molecular and periodic solids with different spin-orbit coupling strengths.