Accelerated Methane Hydrate Nucleation near Ice: Free Energy Landscape and Kinetic Enhancement
Journal
The Journal of Physical Chemistry C
Journal Volume
129
Journal Issue
31
Start Page
14289
End Page
14298
ISSN
19327447
Date Issued
2025-07-28
Author(s)
Abstract
Methane hydrates commonly form beneath the seafloor and in polar regions, where nucleation kinetics can be significantly influenced by nearby ice interfaces. In this work, we perform 200 unbiased molecular dynamics (MD) simulations to investigate the kinetics and thermodynamics of methane hydrate nucleation near ice using a rigorous mean first-passage time (MFPT) analysis. At 250 K, 50 MPa, and 5.8 mol % methane, the nucleation rate of methane hydrate near the ice interface is found to be more than two times higher than in bulk solution. This enhancement is attributed to changes in the free energy landscape induced by the ice interface, which lowers both the critical nucleus size and nucleation barrier (n* = 7.0 and ΔG* = 7.3 kBT near ice, compared to n* = 8.0 and ΔG* = 9.1 kBT in bulk). Spatially resolved analysis reveals that the nucleation rate is maximized at a distance of about 30 Å from the ice surface. The MFPT and spatial distribution results together suggest the existence of a saddle point in the nucleation free energy surface at this intermediate distance and cluster size. These findings offer new insights into the mechanisms of methane hydrate nucleation near ice and establish a methodological framework for studying heterogeneous nucleation in complex interfacial environments.
SDGs
Publisher
American Chemical Society
Type
journal article