First-principles study of structural, vibrational and dielectric properties of double perovskites Ba2LnSbO6 (Ln = Sm, Gd, Dy and Y)

The structural, vibrational and dielectric properties of Ba(2)LnSbO(6) (Ln = Sm, Gd, Dy and Y) type double perovskites in the space group Fm (3) over bar m have been investigated for the first time using the pseudopotential plane wave method based on density functional theory (DFT) under local density approximation (LDA) and linear response formalism. The lattice constants, along with the Raman and the infrared wave-numbers at zone center are calculated and assigned. The calculated values of the lattice constants, Raman and the infrared wavenumbers are in very good agreement with respective experimental values. The bulk modulus, pressure derivative, Born effective charges and dielectric constants have also been calculated and discussed. (c) 2012 Elsevier B.V. All rights reserved.