Effect of pressure on the carbon dioxide hydrate-water interfacial free energy along its dissociation line

TL;DR

This study uses advanced computer simulations to analyze how pressure influences the interfacial free energy of CO₂ hydrate-water systems along the dissociation line, revealing a decreasing trend with increasing pressure.

Contribution

It extends previous simulation work to quantify pressure effects on interfacial free energy, providing insights not accessible through experiments alone.

Findings

Interfacial free energy decreases with pressure between 100 and 1000 bar.

Simulation results agree well with existing experimental data.

Pressure influences the thermodynamic parameters of hydrate-water interfaces.

Abstract

We investigate the effect of pressure on the carbon dioxide (CO$_{2}$) hydrate-water interfacial free energy along its dissociation line using advanced computer simulation techniques. In previous works, we have determined the interfacial energy of the hydrate at $400 \,\text{bar}$ using the TIP4P/ice and TraPPE molecular models for water and CO$_{2}$, respectively, in combination with two different extensions of the Mold Integration technique [J. Chem. Phys. 141, 134709 (2014)]. Results obtained from computer simulation, $29(2)$ and $30(2)\,\text{mJ/m}^{2}$, are found to be in excellent agreement with the only two measurements that exist in the literature, $28(6)\,\text{mJ/m}^{2}$ determined by Uchida et al. [J. Phys. Chem. B 106, 8202 (2002)] and $30(3)\,\text{mJ/m}^{2}$ by Anderson et al. [J. Phys. Chem. B 107, 3507 (2002)]. Since the experiments do not allow to obtain the variation of the interfacial energy along the dissociation line of the hydrate, we extend our previous studies to quantify the effect of pressure on the interfacial energy at different pressures. Our results suggest that there exists a correlation between the interfacial free energy values and the pressure, i.e., it decreases with the pressure between $100$ and $1000\,\text{bar}$. We expect that the combination of reliable molecular models and advanced simulation techniques could help to improve our knowledge of the thermodynamic parameters that control the interfacial free energy of hydrates from a molecular perspective.