Hydrogen hydrates: Equation of state and self-preservation effect

• Published in: Fluid phase equilibria Vol. 413; pp. 220 - 228
• Main Authors: Belosudov, Rodion V., Bozhko, Yulia Yu, Zhdanov, Ravil K., Subbotin, Oleg S., Kawazoe, Yoshiyuki, Belosludov, Vladimir R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2016
• Subjects: Clathrate hydrate; Clathrate hydrates; Equation of state; Hydrates; Hydrogen; Hydrogen storage; Lattices; Mathematical models; Molecular dynamics; Molecular structure; Self-preservation effect; Statistical thermodynamic theory; Thermal expansion; Self-preservation effect; Clathrate hydrate; Hydrogen; Statistical thermodynamic theory; Equation of state
• ISSN: 0378-3812; 1879-0224
• DOI: 10.1016/j.fluid.2015.11.031

The thermodynamic properties of the hydrogen clathrate hydrate with cubic structure II and hexagonal ice Ih have been investigated using both lattice dynamics and molecular dynamics methods with the aim of predicting the existence of the self-preservation phenomenon in the hydrogen hydrate. The statistical thermodynamics model with modifications describing host lattice relaxation, guest–guest interactions and the quantum nature of guest behavior in clathrate hydrates has been applied to calculate the thermal expansion of the volume for both systems. The calculations show that the hydrate remains in a stable region within the phase diagram because the thermal expansion of the hydrate phase is limited by the thermal expansion of ice. The differences in thermal expansion should lead to the self-preservation effect with the application of additional pressure on the hydrate phase. Molecular dynamics simulations also show that the hydrate phase immersed in the ice phase is stable at ambient pressure, which is below the three-phase ice–hydrate–gas equilibrium conditions due to the formation of a hydrogen bonding network between the ice and hydrate structures. From a practical point of view this effect can be used for the storage and transport of hydrogen in the hydrate form. [Display omitted] •A macroscopic model for the description of the self-preservation effect has been proposed.•The thermal expansion of clathrate hydrates and hexagonal ice Ih has been calculated using a lattice dynamics approach.•The stability of the hydrogen hydrate sphere immersed into the ice matrix has been studied using molecular dynamics methods.•The analysis of hydrogen hydrate-ice interface has been performed.