Investigation of Raman and infrared modes for Sr doped double perovskite oxides Ba2−xSrxMWO6 (M=Ni, Co); for 0≤x≤1.2

A short-range force constant model has been applied to investigate the Raman and infrared modes in Sr doped ordered double perovskite oxides Ba2−xSrxMWO6 (M=Co, Ni); 0≤x≤1.2 (cubic phase) using normal coordinate analysis based on the G-F matrix method. In the present work, calculations on zone centre phonons have been made with three stretching and two bending force constants in its cubic phase (space group: Fm-3m) only. The calculated Raman wave numbers are in well agreement with the available experimental results. The infrared modes are calculated and proposed for the first time. The significant contribution of each force constant towards every Raman and the infrared wave numbers has also been determined by investigating the potential energy distribution.