The surprisingly high activation barrier for oxygen-vacancy migration in oxygen-excess manganite perovskites.
The surprisingly high activation barrier for oxygen-vacancy migration in oxygen-excess manganite perovskites.
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DOI：
10.1039/d0cp01281e
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发表时间：
2020-06
期刊：
影响因子：
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通讯作者：
Jacqueline M. Börgers;R. D. De Souza
中科院分区：
文献类型：
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作者：
Jacqueline M. Börgers;R. D. De Souza
目前对（La，Sr）MnO 3钙钛矿型氧化物中氧空位行为的描述虽然被广泛接受，但忽略了一个明显的差异。在实验研究中报道的氧空位迁移的活化焓值（ΔHmig，v = 1.2-2.4 eV）明显高于计算工作中预测的值（ΔHmig，v = 0.5-1.0 eV）。在这项研究中，我们使用分子动力学模拟研究这种差异的起源。具体而言，我们调查的各种阳离子缺陷（Sr取代基，La空位，Mn空位，这两种类型的阳离子反位）的氧空位（Dv）在正交晶系LaMnO 3中的扩散率的影响。结果表明，阳离子空位的存在使ΔHmig，v的计算值与实验值符合得很好.应用分析模型，我们的结果，我们预测，在锰钙钛矿中含有阳离子空位的Dv的等温值将强烈依赖于氧分压（与标准假设相反）。我们的研究结果模拟点缺陷化学的影响，和氧扩散，锰钙钛矿进行了讨论。
The current description of oxygen-vacancy behaviour in (La,Sr)MnO3 perovskite-type oxides, though widely accepted, ignores a pronounced discrepancy. Values of the activation enthalpy of oxygen-vacancy migration reported in experimental investigations (ΔHmig,v = 1.2-2.4 eV) are substantially higher than those predicted in computational work (ΔHmig,v = 0.5-1.0 eV). In this study we examine the origin of this discrepancy using molecular-dynamics simulations. Specifically we investigate the effect of various cation defects (Sr substituents, La vacancies, Mn vacancies, both types of cation antisites) on the diffusivity of oxygen vacancies (Dv) in orthorhombic LaMnO3. Our results indicate that the presence of cation vacancies can bring the computational values of ΔHmig,v into good agreement with experimental data. Applying an analytical model to our results, we predict that isothermal values of Dv in manganite perovskites containing cation vacancies will depend strongly on oxygen partial pressure (contrary to the standard assumption). The implications of our results for modelling the point-defect chemistry of, and oxygen diffusion in, manganite perovskites are discussed.