A novel nanocrystalline metal–organic framework (MOF), ZnPurBr, was recently discovered to undergo an unusual thermal solid–solid phase transition, resulting in a stable high-temperature phase structure, ZnPurBr-HT. In order to fully elucidate this fascinating phase transition, the structural, electronic, optical, and mechanical properties of the ZnPurBr high and low temperature phases are thoroughly investigated through first-principles calculations. This study confirms the retention of the metal tetrahedral bonding and the integrity of the framework during phase transition. Calculations on the electronic and optical properties show that ZnPurBr is a semiconductor and has low refractive indexes at both phases; however, increases in the dielectric constants and the plasmon frequency upon going through the phase transition can be clearly captured. Tensorial analysis of the elastic constants for both phases shows that the high temperature phase is stiffer than its low temperature counterpart, but less anisotropic. Importantly, the techniques used for the modeling and physical properties calculations can be easily be applied to other MOFs, which can certainly reveal many of the interesting features hitherto undiscovered.

中文翻译：

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揭示 ZnPurBr-MOF 的电子结构、机械和介电特性：从头算计算

最近发现一种新型纳米晶金属-有机骨架 (MOF) ZnPurBr 经历了不寻常的热固-固相变，从而产生了稳定的高温相结构 ZnPurBr-HT。为了充分阐明这种迷人的相变，通过第一性原理计算彻底研究了 ZnPurBr 高温和低温相的结构、电子、光学和机械性能。该研究证实了相变过程中金属四面体键的保留和框架的完整性。对电子和光学性质的计算表明，ZnPurBr 是一种半导体，两相都具有低折射率；然而，可以清楚地捕捉到介电常数和等离子体频率在经历相变时的增加。两相弹性常数的张量分析表明，高温相比低温相更硬，但各向异性较小。重要的是，用于建模和物理性质计算的技术可以很容易地应用于其他 MOF，这当然可以揭示许多迄今为止尚未发现的有趣特征。