Generalized Form for Finite-Size Corrections in Mutual Diffusion Coefficients of Multicomponent Mixtures Obtained from Equilibrium Molecular Dynamics Simulation

The system-size dependence
of computed mutual diffusion coefficients
of multicomponent mixtures is investigated, and a generalized correction
term is derived. The generalized finite-size correction term was validated
for the ternary molecular mixture chloroform/acetone/methanol as well
as 28 ternary LJ systems. It is shown that only the diagonal elements of the Fick matrix
show system-size dependency. The finite-size effects of these elements
can be corrected by adding the term derived by Yeh and Hummer (J. Phys. Chem. B 2004, 108, 15873–15879). By performing an eigenvalue analysis of the
finite-size effects of the matrix of Fick diffusivities we show that
the eigenvector matrix of Fick diffusivities does not depend on the
size of the simulation box. Only eigenvalues, which describe the speed
of diffusion, depend on the size of the system. An analytic relation
for finite-size effects of the matrix of Maxwell–Stefan diffusivities
was developed. All Maxwell–Stefan diffusivities depend on the
system size, and the required correction depends on the matrix of
thermodynamic factors.