Modified Becke-Johnson calculations using norm-conserving pseudopotential plane-wave approach: Systematic analysis

Abstract

The modified Becke-Johnson potential for exchange and local density approximation for correlation (mBJLDA) approach is proved to provide a highly improved description of the bandgap. This work presents the results of a systematic investigation of the mBJLDA electronic band structure calculations using the norm-conserving pseudopotential (PP) approach, as implemented in the ABINIT code. The considered systems represent different classes of semiconductors and insulators. Moreover, all-electron (AE) mBJLDA potential and screened hybrid functional YS-PBE0 calculations are also performed for comparison purposes. We show that the mBJLDA@PP bandgaps obtained using typical PP's (i.e., valence and semicore electrons are allowed to relax) are generally speaking smaller than that of the mBJLDA@AE approach. This artifact cannot be attributed to a small “c” parameter of the mBJLDA, since we found that this parameter is quite insensitive to the adopted computational method. Interestingly, the number of electrons treated as valence, especially for the cations, can be used as an extra adjustable parameter to improve the mBJLDA@PP bandgaps. In particular, the best agreement with the mBJLDA@AE bandgaps is obtained by including the outer core p electrons as valence. The optimal PP's for mBJLDA@PP calculations are transferable. A similar agreement is also achieved for the binding energies of the semicore d electrons (in the IIB-VI and IIIB-V compounds), upper valence bandwidths and electron effective masses. Sound explanations of the mBJLDA@PP results for the considered electronic structure properties are provided.