Mixing multiple cations can result in a significant configurational entropy, offer a new compositional space with vast tunability, and introduce new computational challenges. For applications such as the two-step solar thermochemical hydrogen (STCH) generation techniques, we demonstrate that using density functional theory (DFT) combined with Metropolis Monte Carlo method (DFT-MC) can efficiently sample the possible cation configurations in compositionally complex perovskite oxide (CCPO) materials, with (La_0.75Sr_0.25)(Mn_0.25Fe_0.25Co_0.25Al_0.25)O₃ as an example. In the presence of oxygen vacancies (V_O), DFT-MC simulations reveal a significant increase of the local site preference of the cations (short-range ordering), compared to a more random mixing without V_O. Co is found to be the redox-active element and the V_O is the preferentially generated next to Co due to the stretched Co–O bonds. A clear definition of the vacancy formation energy (E_v^f) is proposed for CCPO in an ensemble of structures evolved in parallel from independent DFT-MC paths. By combining the distribution of E_v^f with V_O interactions into a statistical model, the oxygen nonstoichiometry (δ), under the STCH thermal reduction and oxidation conditions, is predicted and compared with the experiments. Similar to the experiments, the predicted δ can be used to extract the enthalpy and entropy of reduction using the van’t Hoff method, providing direct comparisons with the experimental results. This procedure provides a full predictive workflow for using DFT-MC to obtain possible local ordering or fully random structures, understand the redox activity of each element, and predict the thermodynamic properties of CCPOs, for computational screening and design of these CCPO materials at STCH conditions.

中文翻译：

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通过组成复杂的钙钛矿氧化物的计算工作流程研究 (La0.75Sr0.25)(Mn0.25Fe0.25Co0.25Al0.25)O3 中的局域有序、畸变和氧化还原活性


混合多种阳离子可能会产生显着的构型熵，提供具有巨大可调性的新组成空间，并带来新的计算挑战。对于两步太阳能热化学制氢（STCH）技术等应用，我们证明使用密度泛函理论（DFT）与大都会蒙特卡罗方法（DFT-MC）相结合可以有效地对成分复杂的钙钛矿氧化物中可能的阳离子构型进行采样(CCPO) 材料，含 (La _0.75 Sr _0.25 )(Mn _0.25 Fe _0.25 Co _0.25 Al _0.25 )O ₃ 为例。在存在氧空位 (V _O ) 的情况下，DFT-MC 模拟揭示了与没有 V _O 。 Co 被发现是氧化还原活性元素，并且由于 Co-O 键的拉伸，V _O 优先于 Co 生成。为从独立 DFT-MC 路径并行演化的结构集合中的 CCPO 提出了空位形成能 (E _v ^f ) 的明确定义。通过将 E _v ^f 与 V _O 相互作用的分布结合到统计模型中，在 STCH 热还原和氧化条件下，氧非化学计量（δ） ，进行预测并与实验进行比较。与实验类似，预测的 δ 可用于使用范特霍夫方法提取还原的焓和熵，从而与实验结果进行直接比较。 该过程提供了完整的预测工作流程，用于使用 DFT-MC 获得可能的局部有序或完全随机结构，了解每个元素的氧化还原活性，并预测 CCPO 的热力学性质，以便在 STCH 条件下计算筛选和设计这些 CCPO 材料。