Performance of the modified Becke-Johnson potential

TL;DR

The paper evaluates the performance of the modified Becke-Johnson potential in the Wien2K code, showing improved but still imperfect agreement with experimental semiconductor band gaps, and discusses limitations in optimizing lattice parameters.

Contribution

It provides a detailed analysis of the mBJLDA potential's effectiveness in predicting semiconductor band gaps and highlights its limitations and the importance of lattice parameter optimization.

Findings

Improved agreement with experimental band gaps compared to previous methods.

Deviations from experimental gaps can exceed 20% in some cases.

Lattice parameter choice significantly affects band gap predictions.

Abstract

Very recently, in the 2011 version of the Wien2K code, the long standing shortcome of the codes based on Density Functional Theory, namely, its impossibility to account for the experimental band gap value of semiconductors, was overcome. The novelty is the introduction of a new exchange and correlation potential, the modified Becke-Johnson potential (mBJLDA). In this paper, we report our detailed analysis of this recent work. We calculated using this code, the band structure of forty one semiconductors and found an important improvement in the overall agreement with experiment as Tran and Blaha [{\em Phys. Rev. Lett.} 102, 226401 (2009)] did before for a more reduced set of semiconductors. We find, nevertheless, within this enhanced set, that the deviation from the experimental gap value can reach even much more than 20%, in some cases. Furthermore, since there is no exchange and correlation energy term from which the mBJLDA potential can be deduced, a direct optimization procedure to get the lattice parameter in a consistent way is not possible as in the usual theory. These authors suggest that a LDA or a GGA optimization procedure is used previous to a band structure calculation and the resulting lattice parameter introduced into the 2011 code. This choice is important since small percentage differences in the lattice parameter can give rise to quite higher percentage deviations from experiment in the predicted band gap value.