National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, 305-8565, Ibaraki, Japan.
Kitami Institute of Technology, 165 Koen-cho, Kitami, 090-8507, Hokkaido, Japan.
Chemphyschem. 2019 Oct 2;20(19):2518-2524. doi: 10.1002/cphc.201900591. Epub 2019 Aug 28.
Understanding the effect of guest species on the host framework is important for the development of structure-based properties of inclusion compounds. Herein, the crystal structures of the noble gas hydrates encapsulating Xe, Kr, and Ar were studied by powder X-ray diffraction measurements. The crystal structures and hydration numbers of these noble gas hydrates were solved by Rietveld refinements using optimized models with the direct-space technique. It was revealed that host cage size of these hydrates changed depending on the type of guest species even though their unit-cell parameters were the same. Based on the structure models obtained, the densities of Xe, Kr, and Ar gas hydrates were also determined to be 1.837, 1.445 and 1.097 g/cm at 93 K, respectively. Our findings, from a crystallographic point of view, may give insight into further understanding the thermodynamic stability and physical properties of gas hydrates encapsulating small guests.
了解客体物种对主体骨架的影响对于研究包合物的结构性质非常重要。在此，通过粉末 X 射线衍射测量研究了包裹 Xe、Kr 和 Ar 的稀有气体水合物的晶体结构。使用直接空间技术优化模型的 Rietveld 精修确定了这些稀有气体水合物的晶体结构和水合数。结果表明，尽管这些水合物的晶胞参数相同，但客体物种的类型决定了主体笼的大小。基于获得的结构模型，还确定了 Xe、Kr 和 Ar 气体水合物在 93 K 时的密度分别为 1.837、1.445 和 1.097 g/cm3。从晶体学的角度来看，我们的发现可能有助于进一步理解包合小分子客体的气体水合物的热力学稳定性和物理性质。
