Fick diffusion coefficients via molecular dynamics: An alternative approach in the Fourier domain

TJP dos Santos and FW Tavares and CRA Abreu, JOURNAL OF MOLECULAR LIQUIDS, 329, 115460 (2021).

DOI: 10.1016/j.molliq.2021.115460

Mutual diffusion coefficient data are required for several systems of scientific and engineering interest to properly describe mass transport phenomena over a wide range of pressures, temperatures, and compositions. In this work, we calculated Fick diffusion coefficients for some CO2 and n-alkane mixtures at high pressures using a new method, which we derived by introducing modifications to the Fourier Correlation Method (FCM) originally proposed by Nichols and Wheeler I&EC Research, 54, 12,156-12,164 (2015). The modified FCM (mFCM) results were validated through comparisons with experimental data and with Fick coefficients calculated by employing well-established Molecular Dynamics methodologies. The new approach has some interesting advantages, such as providing Fick coefficients for molecular systems directly through a single equilibrium calculation, in contrast to traditional methods in which an extra calculation is needed to obtain the so-called thermodynamic factor. It is shown that the new approach considerably reduces the finite-size effect of the simulation box on the calculated diffusion coefficients, which are thus obtained in the thermodynamic limit. (C) 2021 Elsevier B.V. All rights reserved.

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