Molecular Dynamics Characterization of Temperature and Pressure Effects on the Water-Methane Interface

Molecular dynamics characterization of the water-methane, ethane, and propane gas mixture interfaces

Water–methane hydrate interfaces are ubiquitous in oil and gas technologies and in Nature. The structure and properties of this liquid/crystal interface plays a significant role in transport phenomena between the bulk phases. In this paper, we use molecular dynamics techniques to characterize the liquid water–crystalline methane hydrate in the bulk and, particularly, the interface. We show that the interfacial mechanical approach based on the novel constant normal pressure-cross-sectional area (NPNAT) ensemble with a computational slab length equal to the lattice parameter of the methane clathrates can accurately predict the interfacial free energy of a curved interface. Notably, the computational platform for the interfacial tension characterization includes contributions from elastic strains. In the studied temperature and pressure ranges, we find that the interfacial tension slightly increases with temperature upturn or pressure drop due to less disordered orientation and dispersed distribution of the ...

Multiscale Modeling and Simulation of Water and Methane Hydrate Crystal Interface

Characterization of nucleation of methane hydrate crystals: Interfacial theory and molecular simulation

(1) Background: Gas hydrates are historically notable due to their prevalence and influence on operational difficulties in the oil and gas industry. Recently, new technologies involving the formation of gas hydrates to accomplish various applications have been proposed. This has created new motivation for the characterization of rheological and mechanical properties and the study of molecular phenomena in gas hydrates systems, particularly in the absence of oil and under pre-nucleation conditions. (2) Methodology: This work reviews advances in research on the promotion, inhibition, rheology, and mechanical properties of gas hydrates obtained through an integrated material synthesis-property characterization-multi-scale theoretical and computational platform at McGill University. (3) Discussion: This work highlights the findings from previous experimental work by our group and identifies some of their inherent physical limitations. The role of computational research methods in extending experimental results and observations in the context of mechanical properties of gas hydrates is presented. (4) Summary and Future perspective: Experimental limitations due to the length and time scales of physical phenomena associated with gas hydrates were identified, and future steps implementing the integrated experimental-computational platform to address the limitations presented here were outlined.

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An Integrated Experimental and Computational Platform to Explore Gas Hydrate Promotion, Inhibition, Rheology, and Mechanical Properties at McGill University: A Review

We have enhanced our parallel molecular dynamics (MD) simulation software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator, lammps.sandia.gov) to include many new features for accelerated simulation including articulated rigid body dynamics via coupling to the Rensselaer Polytechnic Institute code POEMS (Parallelizable Open-source Efficient Multibody Software). We use new features of the LAMMPS software package to investigate rhodopsin photoisomerization, and water model surface tension and capillary waves at the vapor-liquid interface. Finally, we motivate the recipes of MD for practitioners and researchers in numerical analysis and computational mechanics.

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Andrei I. Draganescu

Papers

Substructured multibody molecular dynamics.