The Dufour and Soret coefficients of isotopic mixtures from equilibrium molecular dynamics calculations

Abstract

The Soret and Dufour cross correlations functions (CCFs), as determined by equilibrium molecular dynamics calculations, are compared for soft sphere and Lennard-Jones (LJ) mixtures. The isotopic mixture was investigated to avoid separate determination of the partial enthalpy of the system. For the LJ system, potential truncation and particle number effects on the thermal diffusion coefficient were additionally studied. Main findings are: (i) Soret and Dufour CCFs are numerically equivalent, but the fluctuations in the latter are more pronounced, particularly for the LJ mixture. (ii) Using a symmetrized form of the tensor occurring in the heat current, differences between the two CCFs are noticeable, when the Stoermer–Verlet integration algorithm is applied. (iii) The particle number dependence of the CCF, and hence of the thermal diffusion coefficient, is very small.