Perturbation approach to ab initio effective mass calculations

A degenerate perturbation $k\cdot p$ approach for effective mass calculations is implemented in the all-electron density functional theory (DFT) package WIEN2k. The accuracy tested on major group IVA, IIIA-VA, and IIB-VIA semiconductor materials. Then, graphene CuI with defects presented as illustrative applications. For states significant Cu-d character additional local orbitals higher principal quantum numbers (more radial nodes) have to be added basis set order converge results of theory. Caveats related a difference between velocity momentum matrix elements are discussed context application method non-local potentials, such Hartree-Fock/DFT hybrid functionals DFT+U.