Investigation of Raman and infrared phonon modes in case of barium bismuth tantalate (BaBi2Ta2O9)

• Raman and infrared spectra are investigated using normal coordinate analysis.
• Seven stretching and seven bending force constants used in the analysis.
• Frequencies have been assigned for the first time in I4/mmm phase.
• For the first time, the symmetry coordinates have been determined.
• The potential energy distribution is also investigated for each normal mode.

The Raman and the infrared wavenumbers in the Aurivillius structure BaBi2Ta2O9 (BBT) having space group I4/mmm (no. 139-D4h17) are investigated using normal coordinate analysis. The calculation of zone center phonons incorporates seven stretching and seven bending force constants. The Raman and the infrared frequencies for BBT have been assigned for the first time in I4/mmm phase. The calculated Raman and infrared wavenumbers are in very good agreement with the observed ones. The potential energy distributions (PED) are also investigated for each normal mode in BBT and the contributions of different force constants to various frequencies are determined.