In hybrid perovskites, the organic molecules and inorganic frameworks exhibit distinct static and dynamic characteristics. Their coupling will lead to unprecedented phenomena, which have attracted wide research interests. In this paper, we employed Deep Potential molecular dynamics (DPMD), a large-scale MD simulation scheme with DFT accuracy, to study $\mathrm{FA/MAPbI_3}$ hybrid perovskites. A spontaneous hybrid nano-domain behavior, namely multiple molecular rotation nano-domains embedded into a single $\mathrm{[PbI_6]^{4-}}$ octahedra rotation domain, was firstly discovered at low temperatures. The behavior originates from the interplay between the long range order of molecular rotation and local lattice deformation, and clarifies the puzzling diffraction patterns of $\mathrm{FAPbI_3}$ at low temperatures. Our work provides new insights into the structural characteristics and stability of hybrid perovskite, as well as new ideas for the structural characterization of organic-inorganic coupled systems.

中文翻译：

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分子-笼耦合效应的有机-无机钙钛矿混合纳米域结构

在杂化钙钛矿中，有机分子和无机骨架表现出明显的静态和动态特性。它们的耦合将导致前所未有的现象，引起了广泛的研究兴趣。在本文中，我们采用深度势分子动力学（DPMD），一种具有 DFT 精度的大规模 MD 模拟方案，来研究 $\mathrm{FA/MAPbI_3}$ 混合钙钛矿。首次在低温下发现了一种自发的混合纳米域行为，即多个分子旋转纳米域嵌入单个 $\mathrm{[PbI_6]^{4-}}$ 八面体旋转域中。该行为源于分子旋转的长程有序与局部晶格变形之间的相互作用，并阐明了 $\mathrm{FAPbI_3}$ 在低温下令人费解的衍射图案。