负热膨胀
热膨胀
衍射
纳米孔
结晶学
粉末衍射
化学
同步加速器
晶体结构
拉曼光谱
大气温度范围
材料科学
分子物理学
纳米技术
光学
物理
热力学
冶金
作者
Nina Lock,Yue Wu,Mogens Christensen,Lisa J. Cameron,Vanessa K. Peterson,Adam J. Bridgeman,Cameron J. Kepert,Bo B. Iversen
摘要
Multi-temperature X-ray diffraction studies show that twisting, rotation, and libration cause negative thermal expansion (NTE) of the nanoporous metal−organic framework MOF-5, Zn4O(1,4-benzenedicarboxylate)3. The near-linear lattice contraction is quantified in the temperature range 80−500 K using synchrotron powder X-ray diffraction. Vibrational motions causing the abnormal expansion behavior are evidenced by shortening of certain interatomic distances with increasing temperature according to single-crystal X-ray diffraction on a guest-free crystal over a broad temperature range. Detailed analysis of the atomic positional and displacement parameters suggests two contributions to cause the effect: (1) local twisting and vibrational motion of the carboxylate groups and (2) concerted transverse vibration of the linear linkers. The vibrational mechanism is confirmed by calculations of the dynamics in a molecular fragment of the framework.
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