Homogeneous nucleation rate of methane hydrate formation under experimental conditions from seeding simulations

• Published in: The Journal of Chemical Physics
• Main Authors: Grabowska, J., Blazquez, S., Sanz, E., Noya, Eva G., Zeron, I. M., Algaba, J., Miguez, J. M., Blas, F. J., Vega, C.
• Other Authors: Ministerio de Ciencia e Innovación (España), Gdańsk University of Technology, Junta de Andalucía, Universidad de Huelva, Centro de Supercomputación de Galicia
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Institute of Physics 2023
• Subjects: Methane hydrate
• Online Access: http://hdl.handle.net/10261/335449; https://doi.org/10.1063/5.0132681; https://doi.org/10.13039/501100005604; https://doi.org/10.13039/501100004837; https://doi.org/10.13039/501100011011; https://doi.org/10.13039/501100006190; https://api.elsevier.com/content/abstract/scopus_id/85150421270

18 pags., 15 figs., 5 tabs. --This paper is part of the JCP Special Topic on Nucleation: Current Understanding Approaching 150 Years After Gibbs. In this work, we shall estimate via computer simulations the homogeneous nucleation rate for the methane hydrate at 400 bars for a supercooling of about 35 K. The TIP4P/ICE model and a Lennard-Jones center were used for water and methane, respectively. To estimate the nucleation rate, the seeding technique was employed. Clusters of the methane hydrate of different sizes were inserted into the aqueous phase of a two-phase gas-liquid equilibrium system at 260 K and 400 bars. Using these systems, we determined the size at which the cluster of the hydrate is critical (i.e., it has 50% probability of either growing or melting). Since nucleation rates estimated from the seeding technique are sensitive to the choice of the order parameter used to determine the size of the cluster of the solid, we considered several possibilities. We performed brute force simulations of an aqueous solution of methane in water in which the concentration of methane was several times higher than the equilibrium concentration (i.e., the solution was supersaturated). From brute force runs, we infer the value of the nucleation rate for this system rigorously. Subsequently, seeding runs were carried out for this system, and it was found that only two of the considered order parameters were able to reproduce the value of the nucleation rate obtained from brute force simulations. By using these two order parameters, we estimated the nucleation rate under experimental conditions (400 bars and 260 K) to be of the order of log10 (J/(m3 s)) = -7(5). The authors acknowledge Project No. PID2019-105898GBC21 from the Ministerio de Educacion y Cultura. They also acknowledge access to supercomputer time from RES under Project No. FI-2022-1-0019. J.G. acknowledges the financial support from the Gdansk University of Technology under Project No. DEC-09/2021/IDUB/II.1/AMERICIUM/ZD grant under the ...