混合杂化钙钛矿MAGe₁₋ₓSnₓI₃中B位原子偏心与分子取向的相互作用
Interplay of B-Site Off-Centering and Molecular Orientations in the Mixed Hybrid Perovskite MAGe1xSnxI3
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中文总结 AI 辅助
研究通过机器学习原子间势分子动力学，揭示了混合杂化钙钛矿MAGe₁₋ₓSnₓI₃中B位原子偏心与MA取向序的竞争及组分依赖关系，明确了无机亚晶格组成对分子有序性的调控机制。
中文摘要 AI 辅助
B位混合是调控卤化物钙钛矿性质的常用策略，在无铅体系MAGe₁₋ₓSnₓI₃中，该策略会引发八面体倾斜与原子偏心的竞争。我们采用机器学习原子间势驱动的大规模分子动力学，绘制了全组分范围内的结构行为：MAGeI₃表现出强极性B位原子偏心，该偏心在接近立方相变前几乎保持恒定，同时甲胺（MA）取向序随温度升高逐渐减弱；相比之下，MASnI₃兼具八面体倾斜与较弱的主要为反极性的原子偏心。合金化后仍呈现类Ge行为，仅当Sn含量超过约65%时才转变为类Sn行为。在高温相中，B位阳离子仍保持局部偏心但方向无序；在富Ge侧，扭曲的无机框架会使柔性MA取向分布偏向受限的优选方向。这种耦合关系表明，无机亚晶格的组成可调控无铅杂化钙钛矿中的分子有序性。
英文摘要
B-site mixing is a common strategy for tuning properties of halide perovskites. In the lead-free system MAGe1-xSn_xI3, it brings tilting and off-centering into competition. Using large-scale molecular dynamics driven by a machine-learned interatomic potential, we map the structural behavior across the full composition range. MAGeI3 exhibits strong polar B-site off-centering that remains nearly constant up to the cubic transition, together with methylammonium (MA) orientational order that weakens progressively on heating. By contrast, MASnI3 combines octahedral tilting with weaker, predominantly antipolar off-centering. Ge-like behavior persists upon alloying and gives way to Sn-like behavior only beyond roughly 65 % Sn. In the high-temperature phases, the B-site cations remain locally off-centered but directionally disordered. On the Ge-rich side, the distorted inorganic framework biases the soft MA orientational landscape toward a restricted set of preferred directions. This coupling shows how the composition of the inorganic sublattice can tune molecular ordering in lead-free hybrid perovskites.
发表机构
- Chalmers University of Technology（查尔姆斯理工大学）
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