Internal vibrations of organic cations in halide perovskites and their analogues could be used to study the crystal structure of these novel semiconductor materials. In this work, we have studied the vibration properties of the 3-cyanopyridinium (3cp⁺ = [3-CN-C5H5NH]⁺) cation in the hybrid organic–inorganic halide post-perovskite (3cp)PbBr₃. For DFT modeling of the experimental Raman spectrum, we have constructed three different models: free cation, minimal stoichiometric cluster and nanocluster. Calculations of a free cation adequately describe most of the internal vibrations. To describe high-wavenumber hydrogen stretching vibrations, and first of all N–H vibrations, it is necessary to use sufficiently large clusters. We show in the cluster approach for crystal field description that it is necessary to include in the cluster not only halogens but also their nearest environment. In this case, agreement with experiment is reached, and further considerations can be put forward about the strength of the hydrogen bond and its role in stabilising the crystal.

中文翻译：

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杂化卤化物后钙钛矿3-氰基吡啶鎓三溴化铅中有机阳离子振动的密度泛函理论研究的簇方法

卤化物钙钛矿及其类似物中有机阳离子的内部振动可用于研究这些新型半导体材料的晶体结构。在这项工作中，我们研究了杂化有机-无机卤化物后钙钛矿(3cp)PbBr _{3中3-氰基吡啶鎓(3cp} ⁺  = [3-CN-C5H5NH] ⁺ )阳离子的振动特性。对于实验拉曼光谱的 DFT 建模，我们构建了三种不同的模型：游离阳离子、最小化学计量簇和纳米簇。自由阳离子的计算充分描述了大部分内部振动。为了描述高波数氢伸缩振动，首先是 N-H 振动，有必要使用足够大的团簇。我们在晶体场描述的簇方法中表明，簇中不仅需要包含卤素，还需要包含它们最近的环境。在这种情况下，与实验达成了一致，可以对氢键的强度及其稳定晶体的作用提出进一步的考虑。