Research Information System
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, vol.121, no.46, 2024 (SCI-Expanded)
The drastic shape deformation that accompanies the structural phase transition in thermosalient materials offers great potential for their applications as actuators and sensors. The microscopic origin of this fascinating effect has so far remained obscure, while for technological applications, it is important to learn how to drive transitions from one phase to another. Here, we present a combined computational and experimental study, in which we have successfully identified the order parameter for the thermosalient phase transition in the molecular crystal 2,7-di([1,1'-biphenyl]-4-yl)fluorenone. Molecular dynamics simulations reveal that the transition barrier vanishes at the transition temperature. The simulations further show that two low-frequency vibrational-librational modes are directly related to the order parameter that describes this phase transition, which is supported by experimental Raman spectroscopy studies. By applying a computational THz pulse with the proper frequency and amplitude we predict that we can photoinduce this phase transition on a picosecond timescale. Significance 2,7-di([1,1'-biphenyl]-4-yl)fluorenone (4DBpFO) crystals exhibit a remarkably rapid solid-state phase transition resulting in a crystal jump. So far the underlying atomistic mechanism is poorly understood, making it an intriguing subject for study. Computationally, we have successfully identified the molecular motions driving the phase transition in 4DBpFO. The transition barrier vanishes at the transition temperature. The simulations predict that the transition can be induced by applying a pulse at the resonant frequency of the relevant motions far below the transition temperature. This brings a high level of control over the phase transition and our computational approach should be transferable to other systems to predict how to selectively trigger changes in these materials.