Exploration of Properties from Both the Bulk and Surface of Iron Silicides: A Unified Theoretical Study
Exploration of Properties from Both the Bulk and Surface of Iron Silicides: A Unified Theoretical Study
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从硅化铁的本体和表面探索性质：统一的理论研究
DOI：
10.1021/acs.jpcc.9b01199
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发表时间：
2019
影响因子：
3.7
通讯作者：
Xiao-Dong Wen
中科院分区：
文献类型：
--
作者：
Xiaodong Sun;Xingwu Liu;Xingchen Liu;Yu Meng;Chang Song;Yong Yang;Yong-Wang Li;Xiao-Dong Wen
通过密度泛函理论、从头算原子热力学和 Wulff 结构相结合的理论研究，评估了硅化铁模型化合物的体相（磁性和热稳定性）和表面（组成、取向和稳定性）特性。磁性是源自体相的特性之一，我们选择磁性作为例子来演示如何将其与当地的化学环境联系起来，以提供深入的理解。我们发现增加与 Fe 中心相邻的配位 Si 原子的数量会导致磁矩减小。为了揭示与铁硅化物表面性质相关的表面结构特征，我们评估了硅化学势 (μSi) 在一定温度 (T) 和 SiH4(PSiH4) 分压范围内对表面热稳定性的影响。事实证明，随着 highTandPSiH4 下 μSi 的增加，富硅表面的热稳定性得到了改善。然后，我们获得了所有可能暴露的面的表面自由能，通过 Wulff 构造建立了合理的晶体模型，从而系统地评估了所有 Fe-Si 模型随 T 和 PSiH4 变化的形貌演化。我们发现低米勒指数刻面更有可能随着 TandPSiH4 的上升而暴露。
The properties from both bulk phases (magnetism and thermal stability) and surface (composition, orientation, and stability) of iron silicide model compounds were evaluated by a theoretical study with a combination of density functional theory, ab initio atomistic thermodynamics, and Wulff construction. Magnetism, one of the properties originated from bulk phases, has been chosen as an example to demonstrate how to correlate it with the local chemical environment to provide an in-depth understanding. We found that increasing the number of coordinative Si atoms adjacent to an Fe center would cause a decrease in magnetic moment. To reveal surface structural features relevant to surface properties of iron silicides, we evaluated the influence of Si chemical potential (μSi) on surface thermal stability over a range of temperature (T) and partial pressure of SiH4(PSiH4). It turns out that the thermal stability of the Si-rich surfaces has been improved with increasing μSiunder highTandPSiH4. We then acquired the surface free energy of all possibly exposed facets, built up reasonable crystalline models via Wulff construction, and thereby systematically assessed morphology evolution of all of the Fe–Si models as a function of changingTandPSiH4. We found that low Miller index facets are more likely to be exposed with the risingTandPSiH4.