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Article - Self-diffusion.pdf (578.17 kB)
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Self-Diffusion Coefficients of Methane/n-Hexane Mixtures at High Pressures: An Evaluation of the Finite-Size Effect and a Comparison of Force Fields

preprint
submitted on 13.08.2019 and posted on 14.08.2019 by Thiago José Pinheiro dos Santos, Charlles Abreu, Bruno Horta, Frederico W. Tavares
Mass transport coefficients play an important role in process design and in compositional grading of oil reservoirs. As experimental measurements of these properties can be costly and hazardous, Molecular Dynamics simulations emerge as an alternative approach. In this work, we used Molecular Dynamics to calculate the self-diffusion coefficients of methane/n-hexane mixtures at different conditions, in both liquid and supercritical phases. We evaluated how the finite box size and the choice of the force field affect the calculated properties at high pressures. Results show a strong dependency between self-diffusion and the simulation box size. The Yeh-Hummer analytical correction [J. Phys. Chem. B, 108, 15873 (2004)] can attenuate this effect, but sometimes makes the results depart from experimental data due to issues concerning the force fields. We have also found that different all-atom and united-atom models can produce biased results due to caging effects and to different dihedral configurations of the n-alkane.

Funding

CNPq, Brazil

CAPES, Brazil

Petrobras, Brazil

Lobo-Carneiro Supercomputer Faculty, UFRJ, Brazil

History

Email Address of Submitting Author

abreu@eq.ufrj.br

Institution

Federal University of Rio de Janeiro

Country

Brazil

ORCID For Submitting Author

0000-0002-6956-4045

Declaration of Conflict of Interest

No conflict of interest.

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