Melting and superheating of sI methane hydrate: molecular dynamics study

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Physics

Background:

• Methane clathrates (or hydrates) are crystalline solids crucial in geology and energy.
• Understanding their stability, especially in superheated states, is vital for various applications.
• Previous studies often relied on classical nucleation theory for predictions.

Purpose of the Study:

• To investigate the melting and decay dynamics of the superheated structure I (sI) methane clathrate.
• To determine the melting curve across a broad pressure range.
• To identify the kinetic stability boundary of the metastable superheated sI methane clathrate.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• Direct coexistence simulations were used to calculate the melting curve.
• Multiple water models (SPC/E, TIP4P/2005, TIP4P/Ice) and a united-atom methane model were utilized.
• Simulations covered pressures up to 5000 bar.

Main Results:

• The melting curve of the sI methane clathrate was successfully calculated.
• The kinetic stability boundary of the superheated metastable sI structure was determined.
• This boundary was found to be significantly higher than predicted by classical nucleation theory.

Conclusions:

• The study provides crucial insights into the behavior of superheated methane clathrates.
• The findings highlight the limitations of classical nucleation theory for these systems.
• Accurate modeling of clathrate stability is essential for geological and energy-related contexts.