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.

中文翻译：

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识别和控制 thermosalient 材料中超快光诱导相变的阶次参数


热凸起材料中伴随结构相变的剧烈形状变形为它们作为致动器和传感器的应用提供了巨大的潜力。到目前为止，这种迷人效果的微观起源仍然不清楚，而对于技术应用，学习如何驱动从一个阶段到另一个阶段的转变非常重要。在这里，我们提出了一项计算和实验相结合的研究，其中我们成功地确定了分子晶体 2,7-二（[1,1'-联苯]-4-基）-芴酮中热显著相变的有序参数。分子动力学模拟表明，过渡势垒在过渡温度下消失。仿真进一步表明，两种低频振动-自由模式与描述这种相变的阶次参数直接相关，这得到了实验拉曼光谱研究的支持。通过应用具有适当频率和幅度的计算太赫兹脉冲，我们预测我们可以在皮秒时间尺度上光诱导这种相变。