Guest-host interactions in mixed CH4-CO2 hydrates: Insights from molecular dynamics simulations

Bernadette R. Cladek; S. Michelle Everett; Marshall T. Mcdonnell; Matthew G. Tucker; David J. Keffer; Claudia J. Rawn

doi:10.1021/acs.jpcc.8b05228

Guest-host interactions in mixed CH₄-CO₂ hydrates: Insights from molecular dynamics simulations

Bernadette R. Cladek, S. Michelle Everett, Marshall T. Mcdonnell, Matthew G. Tucker, David J. Keffer, Claudia J. Rawn

Research output: Contribution to journal › Article › peer-review

23 Scopus citations

Abstract

Classical molecular dynamics simulations of mixed CH₄-CO₂ gas hydrates provide a thorough analysis of the energetics of both pure CH₄ and CO₂ hydrates and three intermediate compositions along the (CH₄)_1-x(CO₂)_x·5.75(H₂O) solid solution. The energy is broken into guest-guest, guest-host, and host-host contributions. Radial distribution functions and three-dimensional density distributions provide insight into the changes in guest orientation and interactions with the host framework as a function of guest composition. Both energetic and structural analyses provide complementary information to previous experimental studies of the system. The experimentally observed isotropic orientation of CH₄ molecules in both small and large cages is confirmed and the description of the anisotropic orientation of CO₂ molecules in the large cage is confirmed and further enhanced. In mixed hydrates, the presence of CH₄ alters the orientation of CO₂, an indication that the interactions between guests, either direct (guest-guest) or mediated through interactions with the host (host-guest), are an important phenomenon in these systems.

Original language	English
Pages (from-to)	19575-19583
Number of pages	9
Journal	Journal of Physical Chemistry C
Volume	122
Issue number	34
DOIs	https://doi.org/10.1021/acs.jpcc.8b05228
State	Published - Aug 30 2018

Funding

*E-mail: [email protected]. ORCID Bernadette R. Cladek: 0000-0001-8538-6827 David J. Keffer: 0000-0002-6246-0286 Funding This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by Oak Ridge National Laboratory (ORNL). The ICE-MAN software suite was utilized for this work, funded by the Laboratory Directed Research and Development at ORNL. This work is supported by the Center for Materials Processing, a Tennessee Higher Education Commission (THEC) Center of Excellence located at the University of Tennessee, Knoxville, and the University of Tennessee Chancellor’s Fellowship. Notes The authors declare no competing financial interest.

Funders	Funder number
THEC
Tennessee Higher Education Commission
Oak Ridge National Laboratory
Laboratory Directed Research and Development
University of Tennessee

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title = "Guest-host interactions in mixed CH4-CO2 hydrates: Insights from molecular dynamics simulations",

abstract = "Classical molecular dynamics simulations of mixed CH4-CO2 gas hydrates provide a thorough analysis of the energetics of both pure CH4 and CO2 hydrates and three intermediate compositions along the (CH4)1-x(CO2)x·5.75(H2O) solid solution. The energy is broken into guest-guest, guest-host, and host-host contributions. Radial distribution functions and three-dimensional density distributions provide insight into the changes in guest orientation and interactions with the host framework as a function of guest composition. Both energetic and structural analyses provide complementary information to previous experimental studies of the system. The experimentally observed isotropic orientation of CH4 molecules in both small and large cages is confirmed and the description of the anisotropic orientation of CO2 molecules in the large cage is confirmed and further enhanced. In mixed hydrates, the presence of CH4 alters the orientation of CO2, an indication that the interactions between guests, either direct (guest-guest) or mediated through interactions with the host (host-guest), are an important phenomenon in these systems.",

author = "Cladek, {Bernadette R.} and Everett, {S. Michelle} and Mcdonnell, {Marshall T.} and Tucker, {Matthew G.} and Keffer, {David J.} and Rawn, {Claudia J.}",

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doi = "10.1021/acs.jpcc.8b05228",

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T2 - Insights from molecular dynamics simulations

AU - Cladek, Bernadette R.

AU - Everett, S. Michelle

AU - Mcdonnell, Marshall T.

AU - Tucker, Matthew G.

AU - Keffer, David J.

AU - Rawn, Claudia J.

PY - 2018/8/30

Y1 - 2018/8/30

N2 - Classical molecular dynamics simulations of mixed CH4-CO2 gas hydrates provide a thorough analysis of the energetics of both pure CH4 and CO2 hydrates and three intermediate compositions along the (CH4)1-x(CO2)x·5.75(H2O) solid solution. The energy is broken into guest-guest, guest-host, and host-host contributions. Radial distribution functions and three-dimensional density distributions provide insight into the changes in guest orientation and interactions with the host framework as a function of guest composition. Both energetic and structural analyses provide complementary information to previous experimental studies of the system. The experimentally observed isotropic orientation of CH4 molecules in both small and large cages is confirmed and the description of the anisotropic orientation of CO2 molecules in the large cage is confirmed and further enhanced. In mixed hydrates, the presence of CH4 alters the orientation of CO2, an indication that the interactions between guests, either direct (guest-guest) or mediated through interactions with the host (host-guest), are an important phenomenon in these systems.

AB - Classical molecular dynamics simulations of mixed CH4-CO2 gas hydrates provide a thorough analysis of the energetics of both pure CH4 and CO2 hydrates and three intermediate compositions along the (CH4)1-x(CO2)x·5.75(H2O) solid solution. The energy is broken into guest-guest, guest-host, and host-host contributions. Radial distribution functions and three-dimensional density distributions provide insight into the changes in guest orientation and interactions with the host framework as a function of guest composition. Both energetic and structural analyses provide complementary information to previous experimental studies of the system. The experimentally observed isotropic orientation of CH4 molecules in both small and large cages is confirmed and the description of the anisotropic orientation of CO2 molecules in the large cage is confirmed and further enhanced. In mixed hydrates, the presence of CH4 alters the orientation of CO2, an indication that the interactions between guests, either direct (guest-guest) or mediated through interactions with the host (host-guest), are an important phenomenon in these systems.

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Guest-host interactions in mixed CH₄-CO₂ hydrates: Insights from molecular dynamics simulations

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