AI 中文总结
本研究结合第一性原理计算等方法，明确Ca-Ce-Ti-Mn钙钛矿的B位局域化学主导氧空位能量学，识别出Ce/Mn平衡区域，其1350℃下氧化还原循环容量优于氧化铈，为热化学制氢材料设计提供规则。
AI 中文摘要
两步热化学水分解由聚光太阳能热驱动，是可再生氢气的可规模化路线，但该过程需要氧化物材料，其氧空位形成能需平衡易还原与有利再氧化特性。钙钛矿固溶体可调控该平衡，但体相化学计量比与局域缺陷能量学的关系仍不明确。本研究结合第一性原理计算、覆盖度约束的特殊准随机结构方法（该方法实现了全部15种对称 distinct 的氧最近邻环境）、可解释的晶体特征模型（其拟合系数直接编码基础Born-Haber热化学）以及微调的缺陷图神经网络，绘制了Ca-Ce-Ti-Mn（CCTM）钙钛矿的氧空位形成能量学图谱。研究发现，B位局域化学主导氧空位形成能$E_\text{v}$：最近邻Mn占比的变化会根据局域Ce含量使$E_\text{v}$偏移1.0-1.5 eV，而A位Ce的变化则贡献更小的、依赖Mn的0.2-0.6 eV偏移。因此，若能通过加工建立并动力学保留短程B位阳离子有序，可在不改变体相组成的情况下调控氧化还原性能。组成空间图谱识别出Ce/Mn平衡区域（$X_\text{Ce}$=0.29-0.33，$X_\text{Mn}$=0.58-0.67），该区域兼具目标$E_\text{v}$窗口内的高空位位点占比、相稳定性与溶解性，其预测的氧化还原循环容量在1350℃下可媲美或超过氧化铈基准，而氧化铈需约1600℃。对三种CCTM组成的测量显示，在接近模型条件的方案下，循环容量随Ce含量单调增加。该设计规则有望推广至相关钙钛矿家族。
英文摘要
Two-step thermochemical water splitting driven by concentrated solar heat is a scalable route to renewable hydrogen, but it requires oxides whose oxygen-vacancy formation energies balance facile reduction with favorable reoxidation. Perovskite solid solutions can tune this balance, but the relationship between bulk stoichiometry and local defect energetics remains poorly understood. Here we map oxygen-vacancy formation energetics across Ca-Ce-Ti-Mn (CCTM) perovskites by combining first-principles calculations with a coverage-constrained special quasirandom structure approach that realizes all fifteen symmetry-distinct oxygen nearest-neighbor environments, an interpretable crystal-feature model whose fitted coefficients directly encode the underlying Born-Haber thermochemistry, and a fine-tuned defect graph neural network. Local B-site chemistry dominates the oxygen-vacancy formation energy $E_\mathrm{v}$: varying the nearest-neighbor Mn fraction shifts $E_\mathrm{v}$ by 1.0-1.5 eV depending on local Ce content, whereas A-site Ce variation contributes a smaller, Mn-dependent shift of 0.2-0.6 eV. Short-range B-site cation order, if it can be established and kinetically retained through processing, is therefore a candidate means of tuning redox performance without changing bulk composition. Composition-space maps identify a Ce/Mn-balanced region ($X_\mathrm{Ce}$ = 0.29-0.33, $X_\mathrm{Mn}$ = 0.58-0.67) combining a high fraction of vacancy sites within the targeted $E_\mathrm{v}$ window with phase stability and solubility, whose predicted redox cycle capacity matches or exceeds the ceria benchmark at 1350 $^\circ$C rather than the roughly 1600 $^\circ$C ceria requires. Measurements on three CCTM compositions show cycle capacity increasing monotonically with Ce content under protocols close to the model conditions. The design rules are expected to transfer to related perovskite families.
Comments16 pages, 6 figures, 3 tables; supplementary information appended (23 pages, 10 figures, 6 tables), 39 pages total. Manish Kumar and Natalia Ali contributed equally. Data and figure-generation scripts at https://github.com/wexlergroup/cctm-screening. VASP inputs and outputs at https://doi.org/10.17172/nomad.6d7e-hvb1
