A lattice dynamical investigation of the Raman and the infrared wavenumbers of SBT (SrBi2Ta2O9)

A short-range force constant model has been applied using normal coordinates to investigate the Raman and the infrared wavenumbers in SrBi2Ta2O9 (SBT) having space group A21am. The calculation of zone center phonons has been made with nine stretching and eight bending force constants. The Raman and the infrared frequencies for SBT have been assigned for the first time in A21am phase. The calculated Raman and infrared wavenumbers are in very good agreement with the observed ones. The potential energy distribution has also been investigated for determining the significance of contribution from each force constant toward the Raman and the infrared wavenumbers.