Application of attractive potential by DFT + U to predict the electronic properties of materials without highly localized bands

It is well known that density functional theory (DFT) underestimates band gaps of materials which have highly localized valence electrons. On the other hand, the predictions of electronic properties of materials, which do not have localized band near the band gap, by DFT are not accurate enough as well. The effect of electronic correlation on properties of this second group of materials such as, in particular, gallium phosphide (GaP) is theoretically studied in this paper. The goal is to find and physically justify a computationally economical but reasonably accurate method to study such materials. The electronic correlation in GaP has been varied by using DFT based methods, such as in DFT + U, with different U-values for gallium d and phosphorus p orbitals. The fact that GaP does not have partially filled localized orbitals, such as 3d orbitals in ZnO, the justification for the use of DFT + U is rather challenging. DFT + U method, as is applied here in an unconventional way to include attractive potentials, correct the shortcoming of DFT in a very economical way by improving both the band gap and mechanical properties. These results will facilitate large supercell calculations for doping or alloying in GaP or similar materials.