Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms

doi:10.1063/1.2919558

	Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms
	Guo, Guang-Jun; Zhang, Yi-Gang; Li, Meng; Wu, Chang-Hua
刊名	JOURNAL OF CHEMICAL PHYSICS
	2008-05-12
卷号	128 期号:19
ISSN号	0021-9606
DOI	10.1063/1.2919558
文献子类	Article
英文摘要	By performing a large scale of molecular dynamics simulations, we analyze 60x10(6) hydration shells of methane to examine whether the dodecahedral water cluster (DWC) can naturally form in methane aqueous solutions-a fundamental question relevant to the nucleation mechanisms of methane hydrate. The analyzing method is based on identifying the incomplete cages (ICs) from the hydration shells and quantifying their cagelike degrees (zeta(C)=0-1). Here, the zeta(C) is calculated according to the H-bond topological network of IC and reflects how the IC resembles the complete polyhedral cage. In this study, we obtain the zeta(C) distributions of ICs in methane solutions and find the occurrence probabilities of ICs reduce with zeta(C) very rapidly. The ICs with zeta(C)>= 0.65 are studied, which can be regarded as the acceptable cagelike structures in appearance. Both increasing the methane concentration and lowering the temperature can increase their occurrence probabilities through slowing down the water molecules. Their shapes, cage-maker numbers, and average radii are also discussed. About 1/3-1/4 of these ICs are face saturated, meaning that every edges are shared by two faces. The face-saturated ICs have the potential to act as precursors of hydrate nucleus because they can prevent the encaged methane from directly contacting other dissolved methane when an event of methane aggregation occurs. The complete cages, i.e., the ICs with zeta(C)=1, form only in the solutions with high methane concentration, and their occurrence probabilities are about 10(-6). Most of their shapes are different from the known hydrate cages, but we indeed observe a standard 5(12)6(2) hydrate cage. We do not find the expected DWC, and its occurrence probability is estimated to be far less than 10(-7). Additionally, the IC analysis proposed in this work is also very useful in other studies not only on the formation, dissociation, and structural transition of hydrates but also on the hydrophobic hydration of apolar solutes. (c) 2008 American Institute of Physics.
WOS关键词	HETEROGENEOUS CRYSTAL-GROWTH ; GAS HYDRATE ; LIQUID WATER ; HYDROPHOBIC HYDRATION ; STRUCTURAL-PROPERTIES ; COMPUTER-SIMULATION ; HYDROGEN GAS ; BULK WATER ; CLATHRATE ; ICE
WOS研究方向	Physics
语种	英语
出版者	AMER INST PHYSICS
WOS记录号	WOS:000256205200032
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/69074]
专题	中国科学院地质与地球物理研究所
通讯作者	Guo, Guang-Jun
作者单位	Chinese Acad Sci, Key Lab Study Earths Deep Interior, Inst Geol & Geophys, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Guo, Guang-Jun,Zhang, Yi-Gang,Li, Meng,et al. Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms[J]. JOURNAL OF CHEMICAL PHYSICS,2008,128(19).
APA	Guo, Guang-Jun,Zhang, Yi-Gang,Li, Meng,&Wu, Chang-Hua.(2008).Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms.JOURNAL OF CHEMICAL PHYSICS,128(19).
MLA	Guo, Guang-Jun,et al."Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms".JOURNAL OF CHEMICAL PHYSICS 128.19(2008).