隐藏缺陷构型的识别与结构分解：HfO$_2$中带电氧双空位的案例研究

中文摘要 AI 辅助

广泛的构型搜索已揭示晶体化合物中的隐藏缺陷结构，然而其局域键合排列如何改变周围原子环境仍不太清楚。我们在氧化铪（HfO$_2$）中研究这一问题，该材料具有能量竞争的单斜（M）、四方（T）和极性正交（PO）多晶型。对于$c$轴氧双空位复合体（$T_c$），在四方晶格约束下，利用密度泛函理论（DFT）弛豫进行局域畸变搜索，识别出一个隐藏的低能构型族（$T_c^{*}$）。对于完全带电的复合体（$2\mathrm{V}_{\mathrm{O}}^{2+}$），使用平滑重叠原子位置（SOAP）描述符进行结构分解，揭示了混合的M、T和PO特征，并得到Hf配位和键几何独立分析的支持。理想化的$T_c$参考结构无势垒地连接到能量最低的混合构型$T_c^{*}$，在受限景观内将能量降低$18.4$ meV/f.u.。释放晶格约束后，我们使用具有晶胞弛豫端点的固态爬坡弹性带计算，比较了到M和PO的转变路径。对于理想化参考结构，相应势垒从$6.9$和$10.1$ meV/f.u.增加到$T_c^{*}$衍生结构的$26.9$和$15.3$ meV/f.u.。M的势垒增加更大，使得PO而非M成为较低势垒分支。本案例研究展示了结构分解如何将隐藏缺陷构型与周围原子环境的变化以及竞争多晶型之间的动力学分支联系起来。

英文摘要

Extensive configurational searches have revealed hidden defect structures in crystalline compounds, yet how their local bonding arrangements modify the surrounding atomic environment remains less well understood. We examine this question in hafnium oxide (HfO$_2$), which hosts energetically competing monoclinic (M), tetragonal (T), and polar orthorhombic (PO) polymorphs. For the $c$-axis oxygen-divacancy complex ($T_c$), a local-distortion search with density-functional theory (DFT) relaxation under tetragonal-lattice confinement identifies a hidden family of low-energy configurations ($T_c^{*}$). For the fully charged complex ($2\mathrm{V}_{\mathrm{O}}^{2+}$), structural decomposition using Smooth Overlap of Atomic Positions (SOAP) descriptors reveals mixed M-, T-, and PO-like character, supported by independent analyses of Hf coordination and bond geometry. The idealized $T_c$ reference connects barrierlessly to the lowest-energy mixed-motif $T_c^{*}$ configuration, lowering the energy by $18.4$ meV/f.u. within the confined landscape. After releasing the lattice constraint, we compare transformation pathways to M and PO using solid-state nudged elastic band calculations with cell-relaxed endpoints. The respective barriers increase from $6.9$ and $10.1$ meV/f.u. for the idealized reference to $26.9$ and $15.3$ meV/f.u. for the $T_c^{*}$-derived structure. The larger increase for M makes PO, rather than M, the lower-barrier branch. This case study shows how structural decomposition connects hidden defect configurations with changes in the surrounding atomic environment and kinetic branching between competing polymorphs.

发表机构

• Daegu Gyeongbuk Institute of Science & Technology (DGIST)（大邱庆北科学技术院）
• Jeonbuk National University（全北国立大学）
• Westlake University（西湖大学）

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