Revisiting eigen displacements of tetragonal BaTiO3: Combined first principle and experimental investigation

Abstract BaTiO3 is a classical ferroelectric studied for last one century for its ferroelectric properties. Lattice dynamics of BaTiO3 is crucial as the utility of devices is governed by phonons. In this work, we show that traditional characterization of the polar phonon modes is ambiguous and often misinterpreted. By combining Raman, Neutron and X-ray diffraction, dielectric spectroscopic observations with first principle calculations, we have re-examined the character of the normal modes of phonons of tetragonal BaTiO3. We obtained Eigen displacements of vibrational modes through DFT calculations and reclassified the polar modes being Slater (Ti–O), Last (Ba–TiO3) and Axe (BO6) vibrations by correlating experimental and theoretical calculations. The study thus provides authentic nomenclature of the polar modes.