Detailed DFT studies of the band profiles and optical properties of antiperovskites SbNCa3 and BiNCa3

Structural, electronic and optical properties of antiperovskite compounds, SbNCa3 and BiNCa3, are studied by using the full-potential linearized augmented plane waves (FP-LAPW) method under the framework of density functional theory (DFT). The exchange-correlation potential is treated by local density approximation (LDA), generalized gradient approximation (GGA-PBEsol) and GGA developed by Engel and Vosko (EV-GGA). Furthermore, the modified Becke-Johnson (mBJ) potential is also applied to attain reliable results for the band gaps of these compounds. The calculated lattice constants are found consistent with the experimentally measured values and other theoretical results. The band profiles show that both of these materials are direct band gap semiconductors of about 1.1 eV gap. The direct band gap nature reveals that they may be effective in optical devices and therefore the optical properties of these compounds like the real and imaginary parts of dielectric function, refractive index and absorption coefficient are also calculated and discussed.