Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms
By performing a large scale of molecular dynamics simulations, we analyze 60×106 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 an...
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craippubl:10.1063/1.2919558 2024-06-23T07:54:38+00:00 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 2008 http://dx.doi.org/10.1063/1.2919558 https://pubs.aip.org/aip/jcp/article-pdf/doi/10.1063/1.2919558/15413365/194504_1_online.pdf en eng AIP Publishing The Journal of Chemical Physics volume 128, issue 19 ISSN 0021-9606 1089-7690 journal-article 2008 craippubl https://doi.org/10.1063/1.2919558 2024-06-13T04:04:42Z By performing a large scale of molecular dynamics simulations, we analyze 60×106 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 (ζC=0−1). Here, the ζC 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 ζC distributions of ICs in methane solutions and find the occurrence probabilities of ICs reduce with ζC very rapidly. The ICs with ζC⩾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 ζC=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 51262 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. Article in Journal/Newspaper Methane hydrate AIP Publishing The Journal of Chemical Physics 128 19 |
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English |
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By performing a large scale of molecular dynamics simulations, we analyze 60×106 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 (ζC=0−1). Here, the ζC 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 ζC distributions of ICs in methane solutions and find the occurrence probabilities of ICs reduce with ζC very rapidly. The ICs with ζC⩾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 ζC=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 51262 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. |
format |
Article in Journal/Newspaper |
author |
Guo, Guang-Jun Zhang, Yi-Gang Li, Meng Wu, Chang-Hua |
spellingShingle |
Guo, Guang-Jun Zhang, Yi-Gang Li, Meng Wu, Chang-Hua Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms |
author_facet |
Guo, Guang-Jun Zhang, Yi-Gang Li, Meng Wu, Chang-Hua |
author_sort |
Guo, Guang-Jun |
title |
Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms |
title_short |
Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms |
title_full |
Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms |
title_fullStr |
Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms |
title_full_unstemmed |
Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms |
title_sort |
can the dodecahedral water cluster naturally form in methane aqueous solutions? a molecular dynamics study on the hydrate nucleation mechanisms |
publisher |
AIP Publishing |
publishDate |
2008 |
url |
http://dx.doi.org/10.1063/1.2919558 https://pubs.aip.org/aip/jcp/article-pdf/doi/10.1063/1.2919558/15413365/194504_1_online.pdf |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_source |
The Journal of Chemical Physics volume 128, issue 19 ISSN 0021-9606 1089-7690 |
op_doi |
https://doi.org/10.1063/1.2919558 |
container_title |
The Journal of Chemical Physics |
container_volume |
128 |
container_issue |
19 |
_version_ |
1802646836578615296 |