The Origin and Dynamics of the Thermosalient Phase Transition in the Molecular Crystal 4-DBpFO

Abstract

This study aims to understand the mechanism and dynamics of the thermosalient structural phase transition in the molecular crystal 4-DBpFO. This transition is accompanied by a sudden and spectacular change in the crystal shape that makes the crystal jump over distances many times its size when it is heated across this transition. A variety of experimental techniques were used, including optical absorbance, fluorescence, linear birefringence, Raman spectroscopy and time-resolved pump-probe spectroscopy techniques, all as a function of temperature. The order parameter and lattice vibration modes responsible for the phase transition were identified by combining the experiment with molecular dynamics simulations results. In addition, strong THz pulses, resonant with the identified vibration modes, were used to trigger the phase transition.