Anharmonic Origin of Giant Thermal Displacements in the Metal–Organic Framework UiO-67
Anharmonic Origin of Giant Thermal Displacements in the Metal–Organic Framework UiO-67
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DOI：
10.1021/acs.jpcc.7b04757
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发表时间：
2017-09
影响因子：
3.7
通讯作者：
K. Svane;Jessica K. Bristow;A. Walsh
中科院分区：
文献类型：
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作者：
K. Svane;Jessica K. Bristow;A. Walsh
机械软材料如混合有机-无机化合物的晶体学通常揭示大的热位移因子和部分占据的晶格位置，这可能是由静态或动态无序引起的。结合从头算晶格动力学和分子动力学模拟揭示了金属有机骨架UiO-67中联苯-4，4 ′-二羧酸（BPDC）连接基团的巨大热位移的起源.两个苯环之间的二面角在±31°处有两个等效的极小值，这不能用谐振子来描述。相反，在实验中观察到的大的热椭球的最小值之间的非谐切换的结果。开关频率被发现是相似的拓扑结构不同的框架IRMOF-10，这表明动态无序是一个普遍的特点，基于BPDC和结构相似的连接器的MOFs。
The crystallography of mechanically soft materials such as hybrid organic–inorganic compounds often reveals large thermal displacement factors and partially occupied lattice sites, which can arise from static or dynamic disorder. A combination of ab initio lattice dynamics and molecular dynamics simulations reveals the origin of the giant thermal displacements in the biphenyl-4,4′-dicarboxylate (BPDC) linker in the metal–organic framework UiO-67. The dihedral angle between the two phenyl rings has two equivalent minima at ±31°, which cannot be described by harmonic phonons. Instead, anharmonic switching between the minima results in the experimentally observed large thermal ellipsoids. The switching frequency is found to be similar in the topologically distinct framework IRMOF-10, suggesting that dynamic disorder is a general feature of MOFs based on BPDC and structurally similar linkers.