Atomistic mechanisms of phase nucleation and propagation in a model two-dimensional system
Atomistic mechanisms of phase nucleation and propagation in a model two-dimensional system
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DOI：
10.1098/rspa.2022.0388
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发表时间：
2022-12
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影响因子：
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通讯作者：
Shuang Fei;Penghao Xiao;Liming Xiong;Wei Gao
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文献类型：
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作者：
Shuang Fei;Penghao Xiao;Liming Xiong;Wei Gao
本文对一个二维六方相和方相之间的固-固相变模型进行了计算研究。采用固态二聚体和轻推弹性带（NEB）方法确定了相形核和扩展的原子机制。二聚体被应用于识别鞍形配置，NEB被应用于使用二聚体的输出来生成过渡最小能量路径（MEP）。原子和细胞的自由度都用于鞍搜索，使我们能够捕捉到相对较小的超细胞的临界核。结果表明，模型材料中的相变是由相邻原子层间的相对位移引起的局部剪切变形触发的。除了传统的逐层相传播，一个有趣的缺陷辅助低势垒传播路径被确定在六边形到正方形的相变。研究表明，使用二聚体方法在探索未知的过渡路径没有先验假设的意义。本研究结果对其他固态和胶体体系的相变机理也有一定的启示。
We present a computational study on the solid–solid phase transition of a model two-dimensional system between hexagonal and square phases under pressure. The atomistic mechanism of phase nucleation and propagation are determined using solid-state Dimer and nudged elastic band (NEB) methods. The Dimer is applied to identify the saddle configurations and NEB is applied to generate the transition minimum energy path (MEP) using the outputs of Dimer. Both the atomic and cell degrees of freedom are used in saddle search, allowing us to capture the critical nuclei with relatively small supercells. It is found that the phase nucleation in the model material is triggered by the localized shear deformation that comes from the relative shift between two adjacent atomic layers. In addition to the conventional layer-by-layer phase propagation, an interesting defect-assisted low barrier propagation path is identified in the hexagonal to square phase transition. The study demonstrates the significance of using the Dimer method in exploring unknown transition paths without a priori assumption. The results of this study also shed light on phase transition mechanisms of other solid-state and colloidal systems.