  We study selected transition metal related point defects in silicon and
silicon carbide semiconductors by a range separated hybrid density functional
(HSE06). We find that HSE06 does not fulfill the generalized Koopmans' Theorem
for every defect which is due to the self-interaction error in the functional
in such cases. Restoring the so-called generalized Koopmans' Condition with a
simple correction in the functional can eliminate this error, and brings the
calculated charge transition levels remarkably close to the experimental data
as well as to the calculated quasi-particle levels from many-body perturbation
theory.
