Raman Scattering Study of Ferroelastic Phase Transition in C₆H₅NH₃Br Crystal

Abstract

The Raman scattering spectra of C₆H₅NH₃Br have been studied above and below the ferroelastic phase transition temperature T_c=27°C. In contradiction with the previous inference based on X-ray diffuse scattering experiments that a transverse optical phonon as well as the transverse acoustic mode becomes unstable at the transition, no soft optical phonon was observed in the present Raman experiment.