Atomistic molecular dynamics simulation of diffusion in binary liquid n-alkane mixtures

Well relaxed atomistic configurations of binary liquid mixtures of n-alkanes, obtained via a new Monte Carlo simulation algorithm [Zervopoulou et al., J. Chem. Phys. 115, 2860 (2001)], have been subjected to detailed molecular dynamics simulations in the canonical ensemble. Four different binary systems have been simulated (C5–C78 at T=474 K, C10–C78 at T=458 K, and C12–C60 at T=403.5 and 473.5 K). Results are presented for the diffusion properties of these mixtures over a range of concentrations of the solvent (lighter component). The self-diffusion coefficients of the n-alkanes, calculated directly from the simulations, are reported and compared with the predictions of two theories: the detailed free volume theory proposed by Vrentas and Duda based on the availability of free volume in the blends, and a combined Rouse diffusant and chain-end free volume theory proposed by Bueche and von Meerwall et al. A direct comparison with recently obtained experimental data [von Meerwall et al., J. Chem. Phys. 111, 750 (1999)] is also presented.