发表机构
Center for High Pressure Science and Technology Advanced Research; School of Physics, Zhejiang University of Technology; Interdisciplinary Center for Quantum Information & State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Physics, Zhejiang University; Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China; Institute of Physics, Chinese Academy of Sciences; School of Physical Sciences, University of Chinese Academy of Sciences（高压科学与技术前沿研究中心; 浙江工业大学物理学院; 浙江大学物理学院量子信息交叉中心及硅与先进半导体材料国家重点实验室; 中国人民大学量子态构建与调控教育部重点实验室; 中国科学院物理研究所; 中国科学院大学物理科学学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过第一性原理计算，发现$AM_2$Al$_9$化合物在压力下会发生保持晶体对称性的同构相变，该相变由层内与层间原子键的键合特性重新分布驱动，为相关研究提供了新平台。
AI 中文摘要
温度、压力和化学掺杂等外部参数可诱导材料发生结构相变。这类相变通常伴随对称性改变，但同构相变是罕见例外，它属于一级相变却保留母结构的对称性。本文采用第一性原理计算，表明$AM_2$Al$_9$化合物（其中$A$为Ba、Ca、Sr或Eu，$M$为Fe、Co或Ni）会发生压力诱导的同构相变。在相变压力下，这些体系出现显著的体积坍缩，同时保持相同的晶体对称性和空间群$P6/mmm$。基于积分晶体轨道哈密顿布居（ICOHP）的键合分析显示，该相变由层内与层间原子键的键合特性重新分布驱动。由于同构相变在单晶中较为罕见，$AM_2$Al$_9$为研究压力下的临界现象、深化对保持对称性的结构相变的理解提供了有前景的平台。
英文摘要
External parameters such as temperature, pressure, and chemical doping can induce structural phase transitions in materials. Although such transitions usually involve a change in symmetry, an uncommon exception is the isostructural phase transition, which is first order yet preserves the symmetry of the parent structure. Using first-principles calculations, we show that $AM_2$Al$_9$ compounds ($A$ = Ba, Ca, Sr, or Eu; $M$ = Fe, Co, or Ni) undergo pressure-induced isostructural phase transitions. At the transition pressure, these systems exhibit a pronounced volume collapse while retaining the same crystal symmetry and space group ($P6/mmm$). Bonding analysis based on the integrated crystal orbital Hamilton population (ICOHP) shows that the transition is driven by a redistribution of bonding character between intralayer and interlayer atomic bonds. Because isostructural transitions are rare in single crystals, $AM_2$Al$_9$ provides a promising platform for investigating critical phenomena under pressure and for deepening our understanding of symmetry-preserving structural transitions.
Comments8 pages, 5 figures
