Zhu Jinlong, Du Shiyu, Yu Xiaohui, Zhang Jianzhong, Xu Hongwu, Vogel Sven C, Germann Timothy C, Francisco Joseph S, Izumi Fujio, Momma Koichi, Kawamura Yukihiko, Jin Changqing, Zhao Yusheng
1] LANSCE, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA [2] National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China [3] HiPSEC, Department of Physics and Astronomy, University of Nevada, Las Vegas, Nevada 89154, USA.
1] T-Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA [2] Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
Nat Commun. 2014 Jun 17;5:4128. doi: 10.1038/ncomms5128.
Carbon monoxide clathrate hydrate is a potentially important constituent in the solar system. In contrast to the well-established relation between the size of gaseous molecule and hydrate structure, previous work showed that carbon monoxide molecules preferentially form structure-I rather than structure-II gas hydrate. Resolving this discrepancy is fundamentally important to understanding clathrate formation, structure stabilization and the role the dipole moment/molecular polarizability plays in these processes. Here we report the synthesis of structure-II carbon monoxide hydrate under moderate high-pressure/low-temperature conditions. We demonstrate that the relative stability between structure-I and structure-II hydrates is primarily determined by kinetically controlled cage filling and associated binding energies. Within hexakaidecahedral cage, molecular dynamic simulations of density distributions reveal eight low-energy wells forming a cubic geometry in favour of the occupancy of carbon monoxide molecules, suggesting that the carbon monoxide-water and carbon monoxide-carbon monoxide interactions with adjacent cages provide a significant source of stability for the structure-II clathrate framework.
一氧化碳笼形水合物可能是太阳系中的一种重要成分。与气态分子大小与水合物结构之间已确立的关系不同，先前的研究表明一氧化碳分子优先形成I型而非II型气体水合物。解决这一差异对于理解笼形物的形成、结构稳定性以及偶极矩/分子极化率在这些过程中所起的作用至关重要。在此，我们报告了在中等高压/低温条件下合成II型一氧化碳水合物的过程。我们证明，I型和II型水合物之间的相对稳定性主要由动力学控制的笼填充和相关的结合能决定。在十六面体笼内，密度分布的分子动力学模拟揭示了八个形成立方几何形状的低能阱，有利于一氧化碳分子占据，这表明一氧化碳-水和一氧化碳-一氧化碳与相邻笼的相互作用为II型笼形物框架提供了重要的稳定性来源。
