Symmetry-Preserving Phase Transitions in AM2Al9 Materials under Pressure
Abstract
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 AM2Al9 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, AM2Al9 provides a promising platform for investigating critical phenomena under pressure and for deepening our understanding of symmetry-preserving structural transitions.
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BibTeX
@misc{zhang2026symmetrypreserving,
title = {{Symmetry-Preserving Phase Transitions in $AM_2$Al$_9$ Materials under Pressure}},
author = {Jian-Feng Zhang and Sheng Xu and Zhong-Yi Lu and Tao Xiang},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.28957},
eprint = {2608.28957},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.28957},
}
RIS
TY - UNPB
TI - Symmetry-Preserving Phase Transitions in AM_2Al_9 Materials under Pressure
AU - Jian-Feng Zhang
AU - Sheng Xu
AU - Zhong-Yi Lu
AU - Tao Xiang
PY - 2026
DA - 2026/08/29
PB - arXiv
DO - 10.48550/arxiv.2608.28957
UR - https://arxiv.org/abs/2608.28957
AB - 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_2Al_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_2Al_9 provides a promising platform for investigating critical phenomena under pressure and for deepening our understanding of symmetry-preserving structural transitions.
ER -