Temperature dependent vibrational dynamics in crystalline para-terphenyl under high pressure

This study examines the effect of pressure-induced conformation changes on low-temperature vibrational dynamics in crystalline para-terphenyl (pTP). The temperature dependence of homogeneously broadened infrared bands under simultaneous high-pressure and low-temperature conditions is reported. High-pressure induces a conformation change in pTP from a twisted structure at ambient pressure to a planar structure at high pressure (1.35 GPa). The characteristic temperature dependent vibrational dynamics for in-plane versus out-of-plane hydrogen bending modes are correlated with the planarization of the pTP molecule at high-pressure.