Investigation of the mass dependence of self-diffusion coefficients by molecular dynamics calculations: comparison with the Enskog theory

The dependence of the Enskog self-diffusion coefficients D_i,E on mass ratios m_i* = m_i/m₁ in hard sphere mixtures is described by exponential expressions of the form D_i,E = D⁰ _i,E(m*₂)eX_i,E in the case of binary mixtures and D_i,E = D⁰ _iE (m*₂)eX_i,E(m*₃)eXt_i,E in the case of ternary mixtures. D⁰ _i,E are the self-diffusion coefficients in reference mixtures with m*₂ = m*₃ = 1. ex_i,E (i = 1,2) and ext_i,E (i = 1,2,3) are the so called Enskog exponents of binary and ternary mixtures, respectively. Their dependence on particle mass and diameter, mole fraction, density and temperature is discussed and compared with corresponding results of molecular dynamics calculations.