Density functional studies of cubic elpasolites Cs₂NaYX ₆ (X=F, Cl, Br) at ambient and elevated hydrostatic pressure

Density functional calculations are presented for various properties of the elpasolite crystals Cs₂NaYX₆ (X=F, Cl, Br) using the CASTEP module, either in the generalized gradient approximation (GGA) or in the local density approximation (LDA). Specifically, the calculated properties are lattice parameter, density, band gap, elastic constants, bulk modulus, sound velocity, Debye temperature, Grüneisen constant, phonon frequencies and phonon dispersion. The variations of some of these properties with applied pressure have also been calculated. Comparison with experimental data is made where available.