Heyes D M, Brańka A C
Division of Chemistry, School of Biomedical and Molecular Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom.
J Chem Phys. 2005 Jun 15;122(23):234504. doi: 10.1063/1.1931668.
This study explores the effects of interaction softness on the transport properties of simple fluids. The transport coefficients of soft-sphere fluids in which the particles interact via the potential, phi(r)=epsilon(rsigma)(-n), with n in the range from 6 to 1152, have been calculated by molecular-dynamics computer simulation. The self-diffusion coefficient D shear viscosity eta(s), bulk viscosity eta(b), and thermal conductivity lambda were computed over a wide packing fraction range. It was found that the Batschinski-Hildebrand expressions, in which D, eta(s) (-1), eta(b) (-1), and lambda(-1) are assumed to have a linear dependence on the molar volume, represent the data quite well for all n, although least well for the thermal conductivity. The density for which, on extrapolation, each of these quantities is zero, increases with the softness of the interaction (or approximately n(-1)), suggesting that the effective hard-sphere diameter decreases with increasing softness in the small n limit. This treatment leads to simple empirical formulas for the effect of density and n on the effective hard-sphere diameter and packing fraction (in an intermediate range) and the four transport coefficients of these fluids.
本研究探讨了相互作用软度对简单流体输运性质的影响。通过分子动力学计算机模拟，计算了粒子通过势函数(\phi(r)=\epsilon(rsigma)^{(-n)})相互作用的软球流体的输运系数，其中(n)的取值范围为(6)至(1152)。在较宽的填充分数范围内计算了自扩散系数(D)、剪切粘度(\eta(s))、体粘度(\eta(b))和热导率(\lambda)。结果发现，Batschinski-Hildebrand表达式（其中假设(D)、(\eta(s)^{(-1)})、(\eta(b)^{(-1)})和(\lambda^{(-1)})与摩尔体积呈线性关系）对所有(n)的数据拟合效果都相当好，不过对热导率的拟合效果最差。外推时这些量为零的密度随相互作用软度（或近似为(n^{(-1)})）增加，这表明在小(n)极限下，有效硬球直径随软度增加而减小。这种处理方法得出了关于密度和(n)对有效硬球直径、填充分数（在中间范围内）以及这些流体的四个输运系数影响的简单经验公式。
