Theoretical study of structural, electronic, lattice dynamical and dielectric properties of SrAl 2O 4

Abstract

We investigate the structural, electronic, lattice dynamical, and dielectric properties of SrAl 2O 4 within density-function theory. The crystal structure is fully relaxed, and the structural parameters are found to be well consistent with the experimental data. The first pressure derivatives of the bulk modulus are predicted to be 2.5 and 4.3 for local density approximation (LDA) and generalized gradient approximation (GGA), respectively. The electronic band structure shows that the valence band maximum is comprised of O 2p states and a small amount of Al 3s and 3p states, and the conduction band minimum is comprised of Sr 5s and a small amount of O 2p, Al 3s and Al 3p states. The phonon frequencies at the center of the Brillouin zone and the dielectric permittivity tensors are calculated using density-function perturbation theory. The electronic ( ɛ ∞) and static ( ɛ 0) dielectric permittivity tensors are theoretically predicted by the calculations with both LDA and GGA formalisms. The results show that the electronic dielectric permittivity is isotropic, while the static dielectric permittivity exhibits to be somewhat anisotropic due to the dominant ionic contributions in static dielectric permittivity.