AI 中文总结
研究钙钛矿氢氧化物SrTiO$_{3 - x}$H$_x$中阴离子有序，开发含HSE06能量学的CE框架。发现计算能量对DFT + $U$敏感，确定代理值，支持O$_4$H$_2$顺式构型偏好，解决了相关敏感性及阴离子有序未充分探索问题。
AI 中文摘要
钙钛矿氢氧化物中的阴离子有序即使在无序状态下也可能很显著，特别是在非稀释氢浓度下。然而，由于构型复杂性和Ti 3$d$还原，氢化物取代给基于密度泛函理论的精确模拟带来挑战。本文开发了一个包含HSE06杂化DFT能量学的SrTiO$_{3 - x}$H$_x$团簇展开（CE）框架。首先证明计算的混合能量和有序稳定性对DFT + $U$的选择高度敏感，最大变化约为100 meV/阴离子。通过与HSE06计算对比确定$U$ = 3.3 eV作为HSE06代理，可在限制昂贵的HSE06计算到关键构型的同时进行广泛构型探索。基态有序、八面体构型与结构稳定性之间的相关性以及CE模型的MC采样都支持SrTiO$_{3 - x}$H$_x$中对O$_4$H$_2$顺式构型的强烈偏好，此前该顺式偏好被忽视，其每个氢化物稳定约200 meV，与报道的阴离子迁移和极化子形成能量相当。本研究解决了基于CE的有序分析对DFT + $U$的敏感性以及钙钛矿氢氧化物中阴离子有序此前未充分探索的问题。
英文摘要
Anion ordering in perovskite oxyhydrides can remain significant even in disordered states, particularly at non-dilute hydrogen concentrations. Nevertheless, hydride substitution poses challenges for accurate simulations based on density functional theory due to configurational complexity and Ti 3$d$ reduction. Here, we develop a cluster expansion (CE) framework for SrTiO$_{3-x}$H$_x$ incorporating HSE06 hybrid-DFT energetics. We first demonstrate that calculated mixing energies and ordering stability are highly sensitive to the choice of DFT+$U$, with maximum variations on the order of 100 meV/anion. We benchmark ordering energetics against HSE06 calculations and identify $U$ = 3.3 eV as an HSE06 proxy, which enables extensive configurational exploration while limiting costly HSE06 calculations to key configurations for efficient learning of ordering energetics. Together, ground-state orderings, correlations between octahedral configurations and structural stability, and MC sampling of CE models all support a strong preference for the O$_4$H$_2$ cis configuration in SrTiO$_{3-x}$H$_x$, in which two hydride ions occupy first-nearest-neighbor anion sites. This cis-type preference was overlooked in previous ATiO$_{3-x}$H$_x$ studies, despite its sizable stabilization of ~200 meV per hydride comparable to reported anion-migration and polaron-formation energies. This study addresses both the previously underexplored sensitivity of CE-based ordering analyses to DFT+$U$ and anion-ordering in perovskite oxyhydrides.
