Arrangement in La1/3NbO3 Obtained by First-Principles Density Functional Theory with Cluster Expansion and Monte Carlo Simulation
Arrangement in La1/3NbO3 Obtained by First-Principles Density Functional Theory with Cluster Expansion and Monte Carlo Simulation
复制标题
利用第一性原理密度泛函理论与簇展开和蒙特卡罗模拟获得La1/3NbO3中的排布
DOI：
10.1021/acs.jpcc.0c01350
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Toru Asaka
中科院分区：
文献类型：
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作者：
Zijian Yang;Robyn E Ward;Naoto Tanibata;Hayami Takeda;Masanobu Nakayama;Toru Asaka
LixLa(1-x)/ 3nbo3是一种缺乏a位的钙钛矿材料，具有结构依赖的离子电导率。与La2/3TiO3相比，la1 / 3nbo3具有更大的晶胞体积、更低的La3+离子浓度和更高的固有空位浓度。因此，它应该表现出更高的锂离子电导率，因此，是所有陶瓷锂二次电池或快速锂离子传输固态电解质电池的良好候选者。然而，实验观察却显示出相反的结果。关于局部原子排列的信息将有助于分析理论和实验结果之间的差距。从头算密度泛函理论计算对于计算原子排布和能量是有用的。然而，由于电池尺寸的限制，不能使用从头计算观察到La/Li/空位排列中的长程有序。在本研究中，利用集群扩展和蒙特卡罗模拟来弥补这一差距。计算结果再现了富贫拉层沿轴方向交替叠加的现象，与实验结果一致。此外，还发现了富la层的两种可能的调制结构。这些应该有助于解释低于预期的离子电导率和材料中可能的锂离子迁移途径。基于所提出的蒙特卡罗模拟，我们得出闭合和条纹两种低能结构在实际系统中可能共存的结论。实验研究中的调制结构可能是由这两种排列组成的无数纳米畴。如果大多数结构在室温下呈封闭排列，则大多数Li离子将被捕获在封闭排列中的周期单元的中心。这可以解释LixLa(1-x)/3NbO3中Li离子电导率低于预期的原因。
LixLa(1–x)/3NbO3is an A-site-deficient perovskite material that exhibits structure-dependent ionic conductivity. La1/3NbO3has a larger unit cell volume, lower concentration of La3+ions, and higher concentration of intrinsic vacancies than La2/3TiO3. As such, it should exhibit higher Li ion conductivity and, therefore, be a good candidate for all ceramic Li secondary batteries or fast Li ion transport solid-state electrolyte batteries. However, experimental observations show otherwise. Information on the local atomic arrangements would facilitate the analysis of the gap between the theoretical and experimental results. Ab initio density functional theory calculations are useful for calculating the atomic arrangements and energies. However, because of cell size limitations, long-range ordering in La/Li/vacancy arrangements cannot be observed using ab initio calculations. In this study, cluster expansion and Monte Carlo simulations were utilized to bridge this gap. The computational results reproduce the stacking of alternate La-rich and La-poor layers along thec-axis, consistent with the experimental data. In addition, two possible modulated structures for the La-rich layers were discovered. These should help explain the lower-than-expected ionic conductivity and the possible Li ion migration pathways in the material. Based on the presented Monte Carlo simulations, we conclude that the two types of low-energy structures, the closed and striped arrangements, may coexist in the real system. The modulated structures in experimental studies are likely to be numberless nanodomains composed of these two arrangements. If the majority of the structure shows a closed arrangement at room temperature, most of the Li ions will be trapped at the center of the periodic units in the closed arrangement. This could explain the lower-than-expected Li ion conductivity in LixLa(1–x)/3NbO3.