The role of screening in the density functional applied on transition metal defects in semiconductors

TL;DR

This paper investigates the effectiveness of the HSE06 density functional in modeling transition metal defects in semiconductors, identifying self-interaction errors and proposing a correction to improve accuracy against experimental and many-body theory data.

Contribution

It demonstrates that a simple correction to the HSE06 functional can restore the generalized Koopmans' Condition, enhancing the accuracy of defect level predictions.

Findings

HSE06 does not always satisfy Koopmans' Theorem for these defects.

A correction improves the agreement with experimental data.

Charge transition levels are more accurately predicted after correction.

Abstract

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.