In this study, we explore how the orientation of oxygen vacancy channels (OVCs) in SrFeO_2.5 and SrCoO_2.5 thin films is influenced by the metal–oxygen bonds in their octahedral and tetrahedral coordination environments. Using density-functional theory (DFT) calculations, we found that energy changes due to applied strain are driven primarily by the octahedral Fe–O bonds in SrFeO_2.5, leading to a strain-induced transition between perpendicular and parallel OVCs relative to the substrate. In contrast, the tetrahedral Co–O bonds in SrCoO_2.5 primarily drive energy changes due to applied strain, resulting in a parallel OVC orientation regardless of the strain state. These computational findings are supported by experimental results obtained through molecular beam epitaxy (MBE) synthesis, X-ray diffraction (XRD), and scanning transmission electron microscopy (STEM) analysis. Our research underscores the critical role of metal–oxygen coordination environments in predicting and tailoring the properties of strained complex oxide thin films, providing a comprehensive understanding of the mechanisms governing vacancy ordering in brownmillerite structures.

中文翻译：

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八面体和四面体配位影响 SrCoO2.5 和 SrFeO2.5 薄膜中氧空位通道的排序


在这项研究中，我们探讨了 SrFeO _2.5 和 SrCoO _2.5 薄膜中氧空位通道 （OVC） 的取向如何受到其八面体和四面体配位环境中金属-氧键的影响。使用密度泛函理论 （DFT） 计算，我们发现由于施加的应变引起的能量变化主要由 SrFeO _2.5 中的八面体 Fe-O 键驱动，导致相对于衬底的垂直和平行 OVC 之间发生应变诱导的转变。相比之下，SrCoO _2.5 中的四面体 Co-O 键主要驱动由于施加的应变而导致的能量变化，无论应变状态如何，都会导致平行的 OVC 取向。这些计算结果得到了通过分子束外延 （MBE） 合成、X 射线衍射 （XRD） 和扫描透射电子显微镜 （STEM） 分析获得的实验结果的支持。我们的研究强调了金属-氧配位环境在预测和定制应变复杂氧化物薄膜特性方面的关键作用，从而全面了解了控制棕米勒石结构中空位排序的机制。