The thermal properties of binary structure sI clathrate hydrate from molecular dynamics simulation

ABSTRACT

In this work, we present temperature dependence of lattice parameter and normalised lattice parameter in the atmospheric pressure and 120 bar and also pressure dependence of unit cell volume and normalised unit cell volume at 150 and 250 K for variety guests with different size, polarity and guest–host hydrogen bonding capability such as trimethylene oxide (TMO), ethylene oxide (EO), formaldehyde (FA), cyclobutane (CB), cyclopropane (CP) and ethane (Et) in the large cages with CH₄ in small cages of sI clathrate hydrates by molecular dynamics simulations. The obtained values of lattice parameters for the guest species are compatible with the experimental values. These clathrate hydrates are simulated with TIP4P/ice four-site water potential. Herein, isobaric thermal expansivity and isothermal compressibility are calculated at a temperature range of 50–250 K and a wide pressure range. These structural properties have been compared for guests which they are isoelectronic and have similar masses but with different size and polarity. We use molecular dynamics simulations to relate microscopic guest properties, like guest–host hydrogen bonding to macroscopic sI clathrate hydrate properties. The temperature dependence of thermodynamic properties such as constant-volume and constant-pressure heat capacity is presented in the atmospheric pressure for these guest species.

KEYWORDS:

• Clathrate hydrate
• lattice parameter
• thermal expansivity
• isothermal compressibility
• specific heat capacity

Acknowledgements

The authors would like to thank Saman Alavi for discussions on clathrate hydrate compounds. H. M. and H. G. thank the University of Yazd for computational support.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Hossein Mohammadi-Manesh http://orcid.org/0000-0003-2825-4099