Studies on single crystal growth of methane-ethane hydrate and its elastic properties

本研究的目的是制备甲烷-乙烷和甲烷-乙烯水合物单晶，并测定这些合成水合物的弹性性质和结构稳定性。将高压拉曼光谱应用于上述单晶，发现乙烯水合物和甲烷-乙烯水合物的I结构分别高达1.6 GPA和1.7 GPA，均高于甲烷水合物。此外，对单晶乙烯和甲烷-乙烯水合物的高压布里渊实验和计算分析表明，乙烯和甲烷-乙烯水合物的I结构具有比甲烷水合物更强的弹性性质。这些结果表明，较大的乙烯分子占据了主体水笼，增加了甲烷-乙烯水合物的结构稳定性。这一研究结果也有助于对深海沉积物中天然气水合物等各种天然气水合物的弹性性质进行估计。

The purposes of this research are to make single crystals of methane-ethane and methane-ethylene hydrates, and to determine the elastic properties and structural stabilities of these synthesized hydrates.We succeeded in growing single crystals of ethylene and methane-ethylene hydrates using a high-pressure diamond anvil cell. By applying the high-pressure Raman spectroscopy to the above single crystals, we have found that the structure I of ethylene and methane-ethylene hydrates exist up to 1.6 GPa and 1.7 GPa, respectively, which are higher than methane hydrate. Furthermore, the high-pressure Brillouin experiments for the single crystalline ethylene and methane-ethylene hydrates and their computational analysis yielded the elastic properties of the structure I of ethylene and methane-ethylene hydrates which are stiffer than those of methane hydrate. These results suggest that the occupation of host water cages by larger ethylene molecule increases the structural stability of methane-ethylene hydrates. The results of this research are also contributed to the estimation of elastic properties of various gas hydrates such as natural methane hydrate in the deep sea deposit.