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Deciphering the Nature of Temperature-Induced Phases of MAPbBr3 by Ab Initio Molecular Dynamics
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-11-28 , DOI: 10.1021/acs.chemmater.2c02453 Sayan Maity 1 , Suraj Verma 1 , Lavanya M. Ramaniah 2 , Varadharajan Srinivasan 1
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-11-28 , DOI: 10.1021/acs.chemmater.2c02453 Sayan Maity 1 , Suraj Verma 1 , Lavanya M. Ramaniah 2 , Varadharajan Srinivasan 1
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We present an ab initio molecular dynamics study of the temperature-induced phases of methylammonium lead bromide (MAPbBr3). We confirm that the low-temperature phase is not ferroelectric and rule out the presence of any overall polarization arising from the motion of the individual sublattices. Our simulations at room temperature resulted in a cubic Pm3̅m phase with no discernible local orthorhombic distortions. At low temperatures, such distortions are shown to originate from octahedral scissoring modes, but they vanish at room temperature. The predicted timescales of MA motion agree very well with experimental estimates, establishing dynamic disordering of the molecular dipoles over several orientational minima at room temperature. We also identify the key modes of the inorganic and organic sublattices that are coupled at all temperatures, mainly through the N–H···Br hydrogen bonds. Estimated lifetimes of the H bonds correlate well with MA dynamics, indicating a strong connection between these two aspects of organic–inorganic hybrid perovskites. We also confirm that, in addition to the disordering of MA orientations, the transition to the cubic phase is also associated with displacive characteristics arising from both MA and Br ions in the lattice.
中文翻译：
通过 Ab Initio 分子动力学破译 MAPbBr3 温度诱导相的性质
我们提出了甲基铵溴化铅 (MAPbBr 3 )温度诱导相的从头算分子动力学研究。我们确认低温相不是铁电的，并排除了由单个子晶格的运动引起的任何整体极化的存在。我们在室温下的模拟结果是立方Pm 3̅ m相位没有可辨别的局部正交畸变。在低温下，这种扭曲显示出源自八面体剪刀模式，但它们在室温下消失。MA 运动的预测时间尺度与实验估计非常吻合，在室温下建立了分子偶极子在几个方向最小值上的动态无序。我们还确定了在所有温度下主要通过 N–H···Br 氢键耦合的无机和有机子晶格的关键模式。H 键的估计寿命与 MA 动力学密切相关，表明有机-无机杂化钙钛矿的这两个方面之间存在很强的联系。我们还确认，除了 MA 方向的混乱之外，
更新日期：2022-11-28
中文翻译：
通过 Ab Initio 分子动力学破译 MAPbBr3 温度诱导相的性质
我们提出了甲基铵溴化铅 (MAPbBr 3 )温度诱导相的从头算分子动力学研究。我们确认低温相不是铁电的，并排除了由单个子晶格的运动引起的任何整体极化的存在。我们在室温下的模拟结果是立方Pm 3̅ m相位没有可辨别的局部正交畸变。在低温下，这种扭曲显示出源自八面体剪刀模式，但它们在室温下消失。MA 运动的预测时间尺度与实验估计非常吻合，在室温下建立了分子偶极子在几个方向最小值上的动态无序。我们还确定了在所有温度下主要通过 N–H···Br 氢键耦合的无机和有机子晶格的关键模式。H 键的估计寿命与 MA 动力学密切相关，表明有机-无机杂化钙钛矿的这两个方面之间存在很强的联系。我们还确认，除了 MA 方向的混乱之外，
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