A lattice dynamical investigation of the Raman and the infrared wavenumbers of Sr2LnTaO6 (Ln = Nd, Gd, Dy, Er, Yb)

A short range force constant model has been applied using normal coordinates for the first time in Sr2LnTaO6 (Ln = Nd, Gd, Dy, Er, Yb) having space group P21/n. The zone center phonons have been calculated with nine stretching and 11 bending force constants. The calculated values of the Raman and the infrared wavenumbers are in good agreement with the observed ones. The potential energy distribution has also been investigated for determining the significance of contribution from each force constant towards the Raman and the infrared wavenumbers.