The behavior of methane-water mixtures under elevated pressures from simulations using many-body potentials

Area of Science:

• Computational chemistry
• Physical chemistry
• Materials science

Background:

• Non-polarizable potentials fail to model methane-water mixtures at high pressures.
• Ab initio simulations are limited by time and length scales for mixing phenomena.

Purpose of the Study:

• To develop and validate a many-body potential for accurate methane-water mixture simulations.
• To investigate methane-water mixing phenomena at elevated pressures and temperatures.

Main Methods:

• Utilized the many-body MB-nrg potential and MBX software for two-phase simulations.
• Performed simulations up to 3 GPa and 500 K with varying methane concentrations.
• Constructed the methane-water equation of state across the phase diagram.

Main Results:

• The MB-nrg potential successfully captures methane-water mixing at relevant scales.
• Stable mixtures were found to be denser than the sum of their components.
• Many-body polarization enhances methane's induced dipole moments by 0.20 D under pressure.

Conclusions:

• Many-body polarization is crucial for understanding methane-water mixture behavior under pressure.
• The simulated system adopts a denser state driven by enthalpic factors.
• The MB-nrg potential provides an accurate and efficient tool for studying such systems.