Lattice dynamical investigations for Raman and infrared frequencies of Te doped Bi1-xTa1-xTe2xO4; 0<or=x<or=0.2.

We have applied short range force constant model and used normal coordinate analysis based on G-F matrix method in investigating for Raman and infrared modes in Te doped Bi1-xTa1-xTe2xO4; 0<or=x<or=0.2 in its orthorhombic phase. The zone centre phonons calculations is made by using six stretching and seven bending force constants in its orthorhombic phase having space group Pnna with four formula units. All zone centre modes have been assigned in this calculation for the first time. The calculated Raman and infrared wave numbers agree satisfactorily with the available experimental results. The significant contribution of each force constant towards calculated Raman and infrared wave numbers has also been made through investigating the potential energy distribution. The Te-atom is present in equal amount at Bi and Ta site in this compound. The role of tellurium atom is exhibiting one mode behaviour in the ternary compound Bi1-xTa1-xTe2xO4 (0<or=x<or=0.2).