DFT estimation of structural parameters and band gaps of III–V (GaP, AlP, InP, BP) and II–VI (BeX, MgX, CdX: X=O, S, Se, Te) semiconductors

In density functional theory (DFT)-based computational methods, electronic properties at optimised atomic position and lattice constants are calculated for semiconducting materials belonging to III–V (GaP, AlP, InP, BP) and II–VI (BeX, MgX, CdX: X =O, S, Se, Te) groups. This paper reports the calculation of equilibrium lattice constants and bulk moduli of the materials under study using five different DFT functionals LDA, PBE, WC, PBEsol and SCAN. The results show that LDA underestimates while PBE overestimates the experimental lattice constants for all these semiconducting materials studied with a mean absolute relative error (%) of the order of 1%. Such trends in LDA and PBE results agree with the earlier reported work. The lattice constants calculated using WC, PBEsol and SCAN are in better agreement with the experiment compared to optB88vdW functional reported by others. On an average, WC and PBEsol functional have been found to be better in estimating the lattice constants and bulk modulus of II–VI binary compounds. We also present the band-gap calculations of the materials under study using different exchange-correlation functionals. The modified Becke–Johnson approximation suggested by Tran and Blaha is found to provide a better agreement with the experimentally reported results than the standard DFT method. (author)