Dynamic Local Structure in Caesium Lead Iodide: Spatial Correlation and Transient Domains
Dynamic Local Structure in Caesium Lead Iodide: Spatial Correlation and Transient Domains
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DOI：
10.1002/smll.202303565
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发表时间：
2023-09-21
期刊：
影响因子：
13.3
通讯作者：
Csanyi, Gabor
中科院分区：
文献类型：
--
作者：
Baldwin, William J.;Liang, Xia;Csanyi, Gabor
金属卤化物钙钛矿是一种结构和性能可调的多功能半导体。它们是高度动态的晶体，具有复杂的八面体倾斜模式和强烈的非调和原子行为。在这些材料的高温、高对称相中，观察到一些复杂的结构特征。局部结构可能与平均结构有很大的不同，有证据表明动态二维结构具有相关的八面体运动形式。然而，对潜在的复杂原子动力学的理解仍然缺乏。在这项工作中，使用基于原子簇展开框架的新机器学习力场研究了无机钙钛矿CsPbI3的局部结构。通过对大尺度模拟观测到的时空相关性分析，揭示了八面体倾角的低频运动意味着双井有效势景观，即使进入三次相也是如此。此外，在两个高对称相中都存在低对称的动态局部区域。这些区域是平面的，并报道了运动的长度和时间尺度。最后，对这些特征的空间排列及其相互作用进行了研究和可视化，提供了更高对称相的局部结构的全面图像。
Metal halide perovskites are multifunctional semiconductors with tunable structures and properties. They are highly dynamic crystals with complex octahedral tilting patterns and strongly anharmonic atomic behavior. In the higher temperature, higher symmetry phases of these materials, several complex structural features are observed. The local structure can differ greatly from the average structure and there is evidence that dynamic 2D structures of correlated octahedral motion form. An understanding of the underlying complex atomistic dynamics is, however, still lacking. In this work, the local structure of the inorganic perovskite CsPbI3 is investigated using a new machine learning force field based on the atomic cluster expansion framework. Through analysis of the temporal and spatial correlation observed during large-scale simulations, it is revealed that the low frequency motion of octahedral tilts implies a double-well effective potential landscape, even well into the cubic phase. Moreover, dynamic local regions of lower symmetry are present within both higher symmetry phases. These regions are planar and the length and timescales of the motion are reported. Finally, the spatial arrangement of these features and their interactions are investigated and visualized, providing a comprehensive picture of local structure in the higher symmetry phases.