发表机构
University of Manchester; University of Oxford; Center for Advanced Systems Understanding; Helmholtz Zentrum Dresden-Rossendorf; TU Dresden（曼彻斯特大学; 牛津大学; 高级系统理解中心; 德累斯顿-罗森多夫亥姆霍兹中心; 德累斯顿工业大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过有限温度密度泛函理论计算，发现电子熵在压缩氧化铁中可驱动多晶型与化学计量比相变，为超快实验中的非热结构转变提供新路径。
AI 中文摘要
电子熵通常被视为结构稳定性的次级修正，但在强电子激发下，它可以成为主要的热力学驱动力。在此，我们表明电子熵可以驱动压缩氧化铁中的多晶型转变和化学计量比相变。利用有限温度密度泛函理论，我们计算了Fe$_2$O、FeO、Fe$_4$O$_5$、Fe$_3$O$_4$以及多种Fe$_2$O$_3$多晶型体（包括$\alpha$-、$\iota$-、$\zeta$-、$\eta$-和$\theta$-Fe$_2$O$_3$）在60–260 GPa压力范围内的电子温度依赖的吉布斯自由能。在60–140 GPa下，电子激发主要重组Fe$_2$O$_3$多晶型体的相对稳定性，驱动从$\iota$-Fe$_2$O$_3$到$\eta$-Fe$_2$O$_3$的转变。在180 GPa下，自由能景观变得强烈竞争，FeO在中间电子温度范围内被稳定，而$\eta$-Fe$_2$O$_3$在更高温度T下变得有利。在220–260 GPa下，低温下最低自由能相是富铁化合物Fe$_2$O，但增加电子温度会稳定FeO。这些结果表明，电子熵不仅能控制固定组成下晶体结构的相对稳定性，还能控制不同氧化铁化学计量比之间的竞争。预测的电子熵驱动的相边界为超快和高能量密度实验中的非热结构转变提供了途径。
英文摘要
Electronic entropy is usually treated as a secondary correction to structural stability, but under strong electronic excitation it can become a primary thermodynamic driving force. Here we show that electronic entropy can drive both polymorphic and stoichiometric phase transformations in compressed iron oxides. Using finite-temperature density functional theory, we calculate the electronic-temperature-dependent Gibbs free energies of Fe$_2$O, FeO, Fe$_4$O$_5$, Fe$_3$O$_4$, and multiple Fe$_2$O$_3$ polymorphs, including $α$-, $ι$-, $ζ$-, $η$-, and $θ$-Fe$_2$O$_3$, over the pressure range 60--260 GPa. At 60-140 GPa, electronic excitation mainly reorganizes the relative stability of Fe$_2$O$_3$ polymorphs, driving transitions from $ι$-Fe$_2$O$_3$ to $η$-Fe$_2$O$_3$. At 180 GPa, the free-energy landscape becomes strongly competitive as FeO is stabilized over an intermediate range of electronic temperature, while $η$-Fe$_2$O$_3$ becomes favourable at higher T. At 220-260 GPa, the lowest-free-energy phase at low T is the Fe-rich compound Fe$_2$O, but increasing electronic temperature stabilizes FeO. These results demonstrate that electronic entropy can control not only the relative stability of crystal structures at fixed composition, but also the competition between different iron-oxide stoichiometries. The predicted electronic-entropy-driven phase boundaries provide a route to nonthermal structural transformations in ultrafast and high-energy-density experiments.
Journal refMatter. Radiat. Extremes 11, 065801 (2026)
