Successive phase transitions were observed for CsSnBr3 and CH3NH3SnBr3 by means of 81Br NQR and DTA. These compounds are isomorphous with each other and have typical cubic perovskite structures at room temperature. However, with decreasing temperature both compounds showed successive phase transitions and complex 81Br NQR spectra at 77 K. In the case of CH3NH3SnBr3, both 81Br NQR and 119Sn Mössbauer spectra changed markedly with decreasing temperature from those at room temperature. These findings suggested a large distortion of the SnBr6 octahedron from the regular one and were interpreted on the basis of the three-center-four-electron bond model. In relation to these structural changes, a broad-line 1H NMR experiment on CH3NH3SnBr3 was also observed in order to determine the effect of the dynamic properties of the cation.
通过81Br NQR和DTA观察到CsSnBr3和CH3NH3SnBr3的连续相变。这些化合物彼此同型,且在室温下具有典型的立方
钙钛矿结构。然而,随着温度降低,这两种化合物在77 K时表现出连续的相变和复杂的81Br NQR谱。在CH3NH3SnBr3的情况下,81Br NQR和119Sn Mössbauer谱随着温度降低,从室温的情况发生了显著改变。这些发现表明SnBr6八面体与常规状态相比有较大的畸变,并基于三中心四电子键模型进行了解释。关于这些结构变化,还对CH3NH3SnBr3进行了宽谱1H NMR实验,以确定阳离子动态性质的影响。