Understanding decomposition and encapsulation energies of structure I and II clathrate hydrates.
Understanding decomposition and encapsulation energies of structure I and II clathrate hydrates.
复制标题
了解结构 I 和 II 笼形水合物的分解和封装能。
DOI：
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发表时间：
2016
影响因子：
4.4
通讯作者：
R. Ohmura
中科院分区：
文献类型：
--
作者：
S. Alavi;R. Ohmura
当在高压和低温条件下用水或冰压缩时，一些气体形成固体气体水合物包合物，其在那些压力下具有比冰更高的熔点。在这项工作中，我们研究了平衡的客人水和水-水的相互作用能，导致形成的笼形水合物相。特别是，分子动力学模拟与准确的水的潜力被用来研究能量的形成结构I（SI）和II（SII）的笼形水合物的甲烷，乙烷和丙烷。的笼形水合物相的解离焓，在相应的阶段的甲烷，乙烷，和丙烷客人的封装焓，和水分子的平均键合焓计算和比较准确的量热测量和以前的经典和量子力学计算，当可用的。甲烷、乙烷和丙烷的包封能稳定了小的和大的sI和sII水合物笼，较大的分子具有较大的包封能。与冰相比，在sI和sII阶段，平均水-水相互作用减弱。冰相和水合物相的货车范德华势能的相对大小相似，但在冰相中，静电相互作用更强。稳定客体-水“疏水”相互作用补偿较弱的水-水相互作用并稳定水合物相。在货车-Platteeuw统计力学理论中使用了一些关于客笼水相互作用的常见假设来预测不同压力-温度条件下的笼形水合物相稳定性。目前的计算表明，这些假设中的一些可能不能准确地反映客体分子和晶格沃茨之间相互作用的物理性质。
When compressed with water or ice under high pressure and low temperature conditions, some gases form solid gas hydrate inclusion compounds which have higher melting points than ice under those pressures. In this work, we study the balance of the guest-water and water-water interaction energies that lead to the formation of the clathrate hydrate phases. In particular, molecular dynamics simulations with accurate water potentials are used to study the energetics of the formation of structure I (sI) and II (sII) clathrate hydrates of methane, ethane, and propane. The dissociation enthalpy of the clathrate hydrate phases, the encapsulation enthalpy of methane, ethane, and propane guests in the corresponding phases, and the average bonding enthalpy of water molecules are calculated and compared with accurate calorimetric measurements and previous classical and quantum mechanical calculations, when available. The encapsulation energies of methane, ethane, and propane guests stabilize the small and large sI and sII hydrate cages, with the larger molecules giving larger encapsulation energies. The average water-water interactions are weakened in the sI and sII phases compared to ice. The relative magnitudes of the van der Waals potential energy in ice and the hydrate phases are similar, but in the ice phase, the electrostatic interactions are stronger. The stabilizing guest-water "hydrophobic" interactions compensate for the weaker water-water interactions and stabilize the hydrate phases. A number of common assumptions regarding the guest-cage water interactions are used in the van der Waals-Platteeuw statistical mechanical theory to predict the clathrate hydrate phase stability under different pressure-temperature conditions. The present calculations show that some of these assumptions may not accurately reflect the physical nature of the interactions between guest molecules and the lattice waters.
影响因子：
4.4
作者：
Cox, Stephen J.;Towler, Michael D.;Michaelides, Angelos
通讯作者：
Michaelides, Angelos