Accurate defect levels obtained from the HSE06 range-separated hybrid functional

Abstract

Defect levels are a problem for standard implementations of density-functional theory and the error also influences the energetics. We demonstrate that the HSE06 functional, which describes the electronic structure of all group-IV semiconductors well (including Ge), gives highly accurate charge transition levels, too, if the defect wave function is host related---independent of localization. The degree of fulfilling the generalized Koopmans' theorem shows the reliability of the results and the highest-occupied eigenvalue always seems to give the correct vertical ionization energy.