Three-phase equilibria of hydrates from computer simulation. III. Effect of dispersive interactions in the methane and carbon dioxide hydrates

Abstract

In this work, the effect of the range of the dispersive interactions in the determination of the three-phase coexistence line of the CO${}_2$ and CH${}_4$ hydrates has been studied. In particular, the temperature ($T_3$) at which solid hydrate, water, and liquid CO${}_2$/gas CH${}_4$ coexist has been determined through molecular dynamics simulations using different cut-off values (from 0.9 to 1.6 nm) for the dispersive interactions. The $T_3$ of both hydrates has been determined using the direct coexistence simulation technique. Following this method, the three phases in equilibrium are put together in the same simulation box, the pressure is fixed, and simulations are performed at different temperatures $T$. If the hydrate melts, then $T>T_3$. Contrary, if the hydrate grows, then $T<T_3$. The effect of the cut-off distance on the dissociation temperature has been analyzed at three different pressures for CO${}_2$ hydrate, namely, $100$, $400$, and $1000\text{bar}$. Then, we have changed the guest and studied the effect of the cut-off distance on the dissociation temperature of the CH${}_4$ hydrate at $400\text{bar}$. Also, the effect of long-range corrections for dispersive interactions has been analyzed by running simulations with homo- and inhomogeneous corrections and a cut-off value of 0.9 nm. The results obtained in this work highlight that the cut-off distance for the dispersive interactions affects the stability conditions of these hydrates. This effect is enhanced when the pressure is decreased, displacing the $T_3$ about $2-4\text{K}$ depending on the system and the pressure.

12 pages, 6 figures

References in corpus (4)

• Solubility of carbon dioxide in water: some useful results for hydrate nucleation
• Three-phase equilibria of hydrates from computer simulation. I. Finite-size effects in the methane hydrate
• Three-phase equilibria of hydrates from computer simulation. II. Finite-size effects in the carbon dioxide hydrate
• Dissociation line and driving force for nucleation of the nitrogen hydrate from computer simulation

Cited by in corpus (4)

• Three-phase equilibria of hydrates from computer simulation. II. Finite-size effects in the carbon dioxide hydrate
• Simulation of the THF hydrate-water interfacial free energy from computer simulation
• Prediction of the univariant two-phase coexistence line of the tetrahydrofuran hydrate from computer simulation
• Dissociation line and driving force for nucleation of the nitrogen hydrate from computer simulation. II. Effect of multiple occupancy