Soret and mass diffusion measurements and molecular dynamics simulations of n-pentane–n-decane mixtures

Soret coefficients and mass diffusion coefficients of three states of the n-pentane–n-decane mixture have been measured by thermal diffusion forced Rayleigh scattering (TDFRS) and are compared with molecular dynamics simulations values. Both equilibrium (EMD), synthetic (S-NEMD), and boundary driven (BD-NEMD) nonequilibrium techniques have been applied to compute the phenomenological and the transport coefficients relevant to the Soret effect. It is found that statistical error on cross-coefficients using equilibrium and dynamical S-NEMD is too high to enable any comparison with experiments, whereas stationary S-NEMD and BD-NEMD methods have statistical error less than ≈35%. S-NEMD simulations have been carried out in the center-of-mass reference frame and the resulting transport coefficients transformed to the center-of-volume frame of reference. The mass diffusion coefficients are sensibly affected by this transformation and show the same weight fraction dependence as the experimental value, although a difference of roughly a factor of 1.4 is found. The Soret coefficients are, as expected, unaffected by the frame of reference transformation and a good agreement between experiment and simulations is found.