Thermally Induced Phase Transition of Cubic Structure II Hydrate: Crystal Structures of Tetrahydropyran-CO2 Binary Hydrate
Thermally Induced Phase Transition of Cubic Structure II Hydrate: Crystal Structures of Tetrahydropyran-CO2 Binary Hydrate
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立方结构 II 水合物的热诱导相变：四氢吡喃-CO2 二元水合物的晶体结构
DOI：
10.1021/acs.jpclett.2c03392
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Ohmura Ryo
中科院分区：
文献类型：
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作者：
Takeya Satoshi;Fujihisa Hiroshi;Alavi Saman;Ohmura Ryo
我们报道了四氢吡喃（THP）和二氧化碳的立方结构II水合物在约140 K以下的热诱导相变。在不同温度下，通过粉末x射线衍射测量来表征相变。小型五边形十二面体512主水笼中co2客体的动态排序，在简单的co2水合物中未被观察到，与从立方结构II（空间群fd -3m，在153 K时细胞尺寸= 17.3202(7)Å）到四边形(空间群fd -3m，在138 K时细胞尺寸= 17.484（4)Å和c= 12.145(1) Å）的对称降低转变同时发生。讨论了客体分子对低温相变的影响，表明可以通过调节大小客体分子的大小和化学结构来改变笼形物水合物的结构和热力学性质。
We report a thermally induced phase transition of cubic structure II hydrates of tetrahydropyran (THP) and CO2below about 140 K. The phase transition was characterized by powder X-ray diffraction measurements at variable temperatures. A dynamical ordering of the CO2guests in small pentagonal dodecahedral 512host water cages, not previously observed in the simple CO2hydrate, occurs simultaneously with the symmetry lowering transition from a cubic structure II (space groupFd-3mwith cell dimensionsa= 17.3202(7) Å at 153 K) to a tetragonal (space groupI41/amdwith cell dimensionsa= 17.484(4) Å andc= 12.145(1) Å at 138 K) unit cell. The effect of guest molecules on the phase transition at low temperatures is discussed, which demonstrates that the clathrate hydrate structures and thermodynamic properties can be modified by adjusting the size and chemical structure of larger and smaller guest molecules.