Microcanonical molecular simulations of methane hydrate nucleation and growth: evidence that direct nucleation to sI hydrate is among the multiple nucleation pathways.
The results of six high-precision constant energy molecular dynamics (MD) simulations initiated from methane-water systems equilibrated at 80 MPa and 250 K indicate that methane hydrates can nucleate via multiple pathways. Five trajectories nucleate to an amorphous solid. One trajectory nucleates to a structure-I hydrate template with long-range order which spans the simulation box across periodic boundaries despite the presence of several defects. While experimental and simulation data for hydrate nucleation with different time- and length-scales suggest that there may exist multiple pathways for nucleation, including metastable intermediates and the direct formation of the globally-stable phase, this work provides the most compelling evidence that direct formation to the globally stable crystalline phase is one of the multiple pathways available for hydrate nucleation.
Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China. guogj@mail.igcas.ac.cn.
Zhengcai
Z
Zhang
Matthew R
MR
Walsh
Guang-Jun
GJ
Guo