Improving the modified Becke-Johnson exchange potential

David Koller, Fabien Tran, and Peter Blaha

Phys. Rev. B 85, 155109 – Published 5 April 2012

 The modified Becke-Johnson exchange potential [F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401 (2009)] (TB-mBJ) yields very accurate electronic band structures and gaps for various types of semiconductors and insulators (e.g., sp semiconductors, noble-gas solids, and transition-metal oxides). However, the TB-mBJ potential has, for a few groups of solids, the tendency to underestimate the band gap. This has led us to examine the possibility to further improve over the original TB-mBJ potential by either reparametrizing its coefficients using a larger test set of solids or defining a parametrization for small-/medium-size band-gap semiconductors only. We also checked alternatives to the average of |∇ρ|/ρ in the unit cell for the determination of parameter c, which determines the amount of the screening contribution. Among these different possibilities, the best one seems to be a reparametrization of the coefficients, which leads to a much more balanced description of the band gaps.

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http://journals.aps.org.sci-hub.cc/prb/abstract/10.1103/PhysRevB.85.155109

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