Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation.
The structure H (sH) of methane hydrate, which has a distinctive structure with large (LL) cages capable of encapsulating multiple methane molecules, has been suggested as a methane reservoir in large icy bodies such as Titan, making it important in planetary science. This high-pressure phase, which...
Published in: | The Journal of Physical Chemistry B |
---|---|
Main Authors: | , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
American Chemical Society
2024
|
Subjects: | |
Online Access: | https://doi.org/10.1021/acs.jpcb.4c01790 https://pubmed.ncbi.nlm.nih.gov/38832921 |
id |
ftpubmed:38832921 |
---|---|
record_format |
openpolar |
spelling |
ftpubmed:38832921 2024-06-23T07:54:38+00:00 Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation. Yoshida, Ken Suhara, Shinnosuke Noguchi, Naoki 2024 Jun 13 https://doi.org/10.1021/acs.jpcb.4c01790 https://pubmed.ncbi.nlm.nih.gov/38832921 eng eng American Chemical Society https://doi.org/10.1021/acs.jpcb.4c01790 https://pubmed.ncbi.nlm.nih.gov/38832921 J Phys Chem B ISSN:1520-5207 Volume:128 Issue:23 Journal Article 2024 ftpubmed https://doi.org/10.1021/acs.jpcb.4c01790 2024-06-13T16:02:00Z The structure H (sH) of methane hydrate, which has a distinctive structure with large (LL) cages capable of encapsulating multiple methane molecules, has been suggested as a methane reservoir in large icy bodies such as Titan, making it important in planetary science. This high-pressure phase, which exists in the GPa range, lends itself to the study of methane states and dynamics using powerful experimental techniques such as IR and Raman spectroscopy. However, the interpretation of the vibrational spectra of methane in the sH structure has been challenging because of the spectral complexities. The signals attributed to the methane molecules in the LL cage, as well as those of the other two cage types, overlap in the spectra. In this study, we investigated the microscopic origins of the shape of the C-H stretching vibration spectrum of methane in the LL cage using ab initio molecular dynamics (AIMD) simulations. For a single methane molecule in the LL cage, the ν3 band of the C-H stretching mode was observed at a higher frequency typical of isolated molecules in vacuum due to the large size of the LL cage. As the number of methane molecules in the LL cage increased beyond one, a tendency to blue-shift with increasing methane occupancy was observed, consistent with a loose-cage-tight-cage model. By characterizing the time correlation function of methane stretching vibrations based on the solvation number of methane and water molecules proximal to methane within the LL cage, we showed that the complicated spectral line shape observed in cases of higher methane occupancy in the LL cage resulted from the wider variation of the solvation shell states. Analysis of the solvation structures of the AIMD trajectories provided interpretations of the experimental spectral line shape, demonstrating the complementary nature of AIMD to the experiment and its effectiveness in analysis. Article in Journal/Newspaper Methane hydrate PubMed Central (PMC) The Journal of Physical Chemistry B 128 23 5727 5734 |
institution |
Open Polar |
collection |
PubMed Central (PMC) |
op_collection_id |
ftpubmed |
language |
English |
description |
The structure H (sH) of methane hydrate, which has a distinctive structure with large (LL) cages capable of encapsulating multiple methane molecules, has been suggested as a methane reservoir in large icy bodies such as Titan, making it important in planetary science. This high-pressure phase, which exists in the GPa range, lends itself to the study of methane states and dynamics using powerful experimental techniques such as IR and Raman spectroscopy. However, the interpretation of the vibrational spectra of methane in the sH structure has been challenging because of the spectral complexities. The signals attributed to the methane molecules in the LL cage, as well as those of the other two cage types, overlap in the spectra. In this study, we investigated the microscopic origins of the shape of the C-H stretching vibration spectrum of methane in the LL cage using ab initio molecular dynamics (AIMD) simulations. For a single methane molecule in the LL cage, the ν3 band of the C-H stretching mode was observed at a higher frequency typical of isolated molecules in vacuum due to the large size of the LL cage. As the number of methane molecules in the LL cage increased beyond one, a tendency to blue-shift with increasing methane occupancy was observed, consistent with a loose-cage-tight-cage model. By characterizing the time correlation function of methane stretching vibrations based on the solvation number of methane and water molecules proximal to methane within the LL cage, we showed that the complicated spectral line shape observed in cases of higher methane occupancy in the LL cage resulted from the wider variation of the solvation shell states. Analysis of the solvation structures of the AIMD trajectories provided interpretations of the experimental spectral line shape, demonstrating the complementary nature of AIMD to the experiment and its effectiveness in analysis. |
format |
Article in Journal/Newspaper |
author |
Yoshida, Ken Suhara, Shinnosuke Noguchi, Naoki |
spellingShingle |
Yoshida, Ken Suhara, Shinnosuke Noguchi, Naoki Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation. |
author_facet |
Yoshida, Ken Suhara, Shinnosuke Noguchi, Naoki |
author_sort |
Yoshida, Ken |
title |
Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation. |
title_short |
Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation. |
title_full |
Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation. |
title_fullStr |
Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation. |
title_full_unstemmed |
Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation. |
title_sort |
effect of cage occupancies on molecular vibrations of methane in structure h clathrate hydrate: ab initio molecular dynamics simulation. |
publisher |
American Chemical Society |
publishDate |
2024 |
url |
https://doi.org/10.1021/acs.jpcb.4c01790 https://pubmed.ncbi.nlm.nih.gov/38832921 |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_source |
J Phys Chem B ISSN:1520-5207 Volume:128 Issue:23 |
op_relation |
https://doi.org/10.1021/acs.jpcb.4c01790 https://pubmed.ncbi.nlm.nih.gov/38832921 |
op_doi |
https://doi.org/10.1021/acs.jpcb.4c01790 |
container_title |
The Journal of Physical Chemistry B |
container_volume |
128 |
container_issue |
23 |
container_start_page |
5727 |
op_container_end_page |
5734 |
_version_ |
1802646837972172800 |