Pressure-driven dimensional evolution and two-dimensional superionic state in AlI<sub>3</sub>

Yanlei Geng; Junwei Li; Jianfu Li; Yong Liu; Jianan Yuan; Saori Imada Kawaguchi; Qingyang Hu; Xiaoli Wang

doi:10.1063/5.0320987

Volume 11 Issue 4

Jul. 2026

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Yanlei Geng, Junwei Li, Jianfu Li, Yong Liu, Jianan Yuan, Saori Imada Kawaguchi, Qingyang Hu, Xiaoli Wang. Pressure-driven dimensional evolution and two-dimensional superionic state in AlI3[J]. Matter and Radiation at Extremes, 2026, 11(4): 047801. doi: 10.1063/5.0320987

Citation:

Yanlei Geng, Junwei Li, Jianfu Li, Yong Liu, Jianan Yuan, Saori Imada Kawaguchi, Qingyang Hu, Xiaoli Wang. Pressure-driven dimensional evolution and two-dimensional superionic state in AlI₃[J]. Matter and Radiation at Extremes, 2026, 11(4): 047801. doi: 10.1063/5.0320987

Citation:

Yanlei Geng, Junwei Li, Jianfu Li, Yong Liu, Jianan Yuan, Saori Imada Kawaguchi, Qingyang Hu, Xiaoli Wang. Pressure-driven dimensional evolution and two-dimensional superionic state in AlI₃[J]. Matter and Radiation at Extremes, 2026, 11(4): 047801. doi: 10.1063/5.0320987

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Pressure-driven dimensional evolution and two-dimensional superionic state in AlI₃

doi: 10.1063/5.0320987

Yanlei Geng^{1, 2, 3
,},
Junwei Li^2
,,
Jianfu Li^{1
,
,
,},
Yong Liu¹,
Jianan Yuan¹,
Saori Imada Kawaguchi⁴,
Qingyang Hu^{2
,
,
,},
Xiaoli Wang^{1
,
,
,}

1.
School of Physics and Electronic Information, Yantai University, Yantai 264005, China
2.
Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China
3.
Synergetic Extreme Condition High-Pressure Science Center, State Key Laboratory of High Pressure and Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
4.
Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan

More Information

Corresponding author: a)Authors to whom correspondence should be addressed: jianfuli@ytu.edu.cn; qingyang.hu@hpstar.ac.cn; and xlwang@ytu.edu.cn
Received Date: 2026-01-04
Accepted Date: 2026-04-03

Available Online: 2026-07-24

Publish Date: 2026-07-24

Abstract

Abstract

Iodide ions can form crystal lattices with large interstitial spaces, making them archetypal systems for investigating superionic phase transitions. Understanding how iodine-based lattices evolve under different thermodynamic conditions is therefore a central problem in condensed matter physics and functional materials design. Aluminum iodide (AlI₃) is a molecular solid crystal with low ionic conductivity under ambient conditions, and it plays important roles in batteries and catalytic applications, motivating exploration of its pressure-tunable ionic transport behavior. Here, we reveal the pressure-induced structural dimensionality evolution in AlI₃ through first-principles structural searches and synchrotron X-ray diffraction (XRD). We identify a sequence of phase transitions: from the molecular P2₁/c phase to a two-dimensional layered rhombohedral (R-3) phase above 1.3 GPa, and subsequently to a one-dimensional chain-like orthorhombic (Cmcm) phase beyond 49 GPa. Notably, in situ laser-heating XRD and ab initio molecular dynamics simulations reveal that the R-3 phase undergoes a transition to a superionic state at high temperatures, where Al³⁺ ions undergo partially disordered, rapid diffusion within the rigid iodine layers. We further demonstrate that the introduction of Al³⁺ vacancies substantially reduces the superionic transition temperature. Our work not only maps the structural evolution of AlI₃ under pressure, but also provides a key reference for the structural design of metal halides under high pressure.

The authors have no conflicts to disclose.
Conflict of Interest
Author Contributions
Yanlei Geng: Data curation (equal); Formal analysis (equal); Writing – original draft (equal). Junwei Li: Data curation (equal). Jianfu Li: Conceptualization (equal); Formal analysis (equal); Writing – review & editing (equal). Yong Liu: Formal analysis (equal). Jianan Yuan: Formal analysis (equal). Saori Imada Kawaguchi: Data curation (equal). Qingyang Hu: Formal analysis (equal); Funding acquisition (equal); Writing – review & editing (equal). Xiaoli Wang: Conceptualization (equal); Formal analysis (equal); Funding acquisition (equal); Project administration (equal); Writing – review & editing (equal).
The data that support the findings of this study are available from the corresponding authors upon reasonable request.

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References(62)

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