Zhu Sheng-Cai, Huang Zhen-Bo, Hu Qingyang, Xu Liang
School of Materials, Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China.
Center for High Pressure Science and Technology Advanced Research, Beijing 100094, P. R. China.
Phys Chem Chem Phys. 2022 Mar 16;24(11):7007-7013. doi: 10.1039/d1cp05803g.
Scandium (Sc) is the lightest non-main-group element and transforms to a host-guest (H-G) incommensurate structure under gigapascal (GPa) pressures. While the host structure is stable over a wide pressure range, the guest structure may exist in multiple forms, featuring different incommensurate ratios, and mixing up to generate long-range "disordered" guest structures. Here, we employed the recently developed global neural network (g-NN) potential and the stochastic surface walking (SSW) global optimization algorithm to explore the global potential energy surface of Sc under various pressures. We probe the global minima structure in a system made of hundreds of atoms and revealed that the solid-phase transition between Sc-I and H-G Sc-II phases is fully reconstructive in nature. Above 62.5 GPa, the pressure will further destabilize the face-centered tetragonal (fct, Sc-IIa) guest structure to a body-centered tetragonal phase (bct, Sc-IIb), while sustaining the host structure. The structural transition mechanism of this work will shed light on the nature of the complex H-G structural modifications in compressed metals.
钪（Sc）是最轻的非主族元素，在吉帕斯卡（GPa）压力下会转变为一种主客体（H-G）非 commensurate 结构。虽然主体结构在很宽的压力范围内是稳定的，但客体结构可能以多种形式存在，具有不同的非 commensurate 比率，并混合形成长程“无序”的客体结构。在这里，我们采用了最近开发的全局神经网络（g-NN）势和随机表面行走（SSW）全局优化算法，来探索不同压力下 Sc 的全局势能面。我们在由数百个原子组成的系统中探测全局极小值结构，并揭示了 Sc-I 和 H-G Sc-II 相之间的固相转变本质上是完全重构的。在 62.5 GPa 以上，压力会进一步使面心四方（fct，Sc-IIa）客体结构不稳定，转变为体心四方相（bct，Sc-IIb），同时保持主体结构。这项工作的结构转变机制将有助于揭示压缩金属中复杂的 H-G 结构修饰的本质。
