Raman scattering study of high-pressure phase transition in thiourea
1High Pressure Physics Division, Bhabha Atomic Research Center, Mumbai 400085, India.
Abstract:
A high-pressure Raman spectroscopic study of phase transitions in thiourea is reported. The changes in the Raman spectra with increasing and decreasing pressure have been followed to a maximum pressure of approximately 11 GPa. We observe several changes in the spectra including splitting of modes, appearance of new modes, and sudden change in the slope of the frequency-pressure curve at several pressures. On the basis of this study, we propose the existence of three more transitions in this system to phases VII, VIII, and IX at approximately 1, 3, and 6.1 GPa, respectively, in addition to the V-VI phase transition at 0.35 GPa reported earlier. All the transitions have been found to be completely reversible. We interpret these changes in terms of symmetry-lowering phase transitions.
Related Concept Videos
Phase Diagram
Phase Transitions: Melting and Freezing
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
Phase Transitions: Sublimation and Deposition
Phase Transitions
Phase Transitions


