FP-APW+lo study of the elastic, electronic and optical properties for the cubic antiperovskite ANSr3 (A=As, Sb and Bi) under pressure effect

Structural, electronic, elastic and optical properties of the cubic-antiperovskite-type ANSr3, with A=As, Sb and Bi, are studied under pressure effect using the full-relativistic version of the full-potential augmented plane wave plus local orbitals method (FP-APW+lo). The exchange–correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). Also we have used Engel and Vosko GGA formalism (GGA-EV) to improve the band gap results. The calculated bulk properties, including lattice constants, bulk moduli and their pressure derivatives are in reasonable agreement with the available data. The elastic constants Cij and their pressure dependences are calculated using the total energy-strain technique. The shear modulus, Young's modulus, Poisson's ratio and Lame's coefficients are estimated in the framework of the Voigt–Reuss–Hill approximation for ideal polycrystalline ANSr3 aggregates. The Debye temperature is estimated from the average sound velocity. Energy band structures show that the investigated materials are direct energy band gap semiconductors. Analysis of the density of states and charge density distribution shows that the bonding is a mixture of covalent and ionic character. For the first time, the real and imaginary parts of the dielectric function ε(ω), the refractive index n(ω), the reflectivity R(ω) and the energy loss function L(ω) are calculated for radiation up to 18 eV.