Pressure-Induced Miscibility Increase of CH₄ in H₂O: A Computational Study Using Classical Potentials.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Geochemistry

Background:

• Methane and water normally demix due to differing polarities.
• Experimental data indicate increased methane solubility in water at high pressures (1-2 GPa) and sub-critical temperatures.
• This phenomenon is relevant to understanding geological processes and chemical engineering applications.

Purpose of the Study:

• To investigate methane solubility in water under high pressure using molecular dynamics simulations.
• To validate classical force fields for methane-water mixtures at elevated pressures.
• To understand the discrepancy between simulated and experimental results for methane solubility.

Main Methods:

• Molecular dynamics simulations were performed using classical force fields.
• Simulations covered various pressure and temperature conditions, including sub-critical and supercritical water.
• The study focused on methane-water mixtures.

Main Results:

• Simulations correctly predicted increased miscibility for methane and supercritical water.
• The models failed to reproduce the experimentally observed increase in methane solubility at high pressures and sub-critical temperatures.
• Current classical force fields may be inadequate for accurately modeling methane-water interactions under these specific conditions.

Conclusions:

• Accurate force fields are needed for methane and methane-water mixtures under high pressure.
• Further development of computational models is required to match experimental observations.
• The study highlights limitations in current simulation methods for predicting solubility under extreme conditions.