标题： 范德华力 In$_2$Se$_3$的多种多型物和相变 显示英文标题

标题： Diverse polymorphs and phase transitions in van der Waals In$_2$Se$_3$

摘要： 范德华力在$_2$硒$_3$中因其独特的性质以及与丰富的多晶型和多晶型相变相关的广泛应用而受到广泛关注。 尽管进行了广泛的研究，巨大的复杂多晶型相空间仍然大多未被探索，其相变的微观机制仍不清楚。 在这里，我们开发了一种高度准确、高效且可靠的机器学习势能（MLP），它不仅有助于精确探索复杂的势能面（PES），还使我们能够以第一性原理精度进行大规模分子动力学（MD）模拟。 我们确定了$\beta''$多晶型的准确结构，并揭示了几种之前未报告的$\beta'$多晶型变体，这些变体表现出动态稳定性和竞争能量，通过特征性的平坦虚频声子带和$\beta$多晶型中独特的墨西哥帽状 PES 得以阐明。 通过MLP加速的分子动力学模拟，我们在不同温度和压力条件下直接观察到$\alpha$、$\beta$、$\beta'$和$\beta''$多形体之间的多形相变，并首次构建了从头算的温度-压力相图，与实验结果有良好一致。 此外，我们的分子动力学模拟揭示了$\beta'$和$\beta''$多形体之间的一种新型应变诱导可逆相变。 这项工作不仅揭示了范德华力在$_2$Se$_3$中的多种多晶型，还为其相变提供了关键的原子洞察，为设计新型功能电子器件开辟了新途径。 显示英文摘要

摘要： Van der Waals In$_2$Se$_3$ has garnered significant attention due to its unique properties and wide applications associated with its rich polymorphs and polymorphic phase transitions. Despite extensive studies, the vast complex polymorphic phase space remains largely unexplored, and the underlying microscopic mechanism for their phase transformations remains elusive. Here, we develop a highly accurate, efficient, and reliable machine-learning potential (MLP), which not only facilitates accurate exploration of the intricate potential energy surface (PES), but also enables us to conduct large-scale molecular dynamics (MD) simulations with first-principles accuracy. We identify the accurate structure of the $\beta''$ polymorph and uncover several previously unreported $\beta'$ polymorph variants exhibiting dynamic stability and competing energies, which are elucidated by characteristic flat imaginary phonon bands and the distinctive Mexican-hat-like PES in the $\beta$ polymorph. Through the MLP-accelerated MD simulations, we directly observe the polymorphic phase transformations among the $\alpha$, $\beta$, $\beta'$, and $\beta''$ polymorphs under varying temperature and pressure conditions, and build for the first time an ab initio temperature-pressure phase diagram, showing good agreement with experiments. Furthermore, our MD simulations reveal a novel strain-induced reversible phase transition between the $\beta'$ and $\beta''$ polymorphs. This work not only unveils diverse polymorphs in van der Waals In$_2$Se$_3$, but also provides crucial atomic insights into their phase transitions, opening new avenues for the design of novel functional electronic devices.