Laghaei Rozita, Nasrabad Afshin Eskandari, Eu Byung Chan
Department of Chemistry and le Regroupement Quebecois sur les Materiaux de Pointe (RQMP), McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 2K6, Canada.
J Phys Chem B. 2005 Mar 31;109(12):5873-83. doi: 10.1021/jp0448245.
The shear viscosity formula derived by the density fluctuation theory in previous papers is computed for argon, krypton, and methane by using the self-diffusion coefficients derived in the modified free volume theory with the help of the generic van der Waals equation of state. In the temperature regime near or above the critical temperature, the density dependence of the shear viscosity can be accounted for by ab initio calculations with the self-diffusion coefficients provided by the modified free volume theory if the minimum (critical) free volume is set equal to the molecular volume and the volume overlap parameter (alpha) is taken about unity in the expression for the self-diffusion coefficient. In the subcritical temperature regime, if the density fluctuation range parameter is chosen appropriately at a temperature, then the resulting expression for the shear viscosity can well account for its density and temperature dependence over the ranges of density and temperature experimentally studied. In the sense that once the density fluctuation range is fixed at a temperature, the theory can account for the experimental data at other subcritical temperatures on the basis of the intermolecular force only; the theory is predictive even in the subcritical regime of temperature. Theory is successfully tested in comparison with experimental data for self-diffusion coefficients and shear viscosity for argon, krypton, and methane.
利用由通用范德瓦尔斯状态方程借助修正自由体积理论推导得到的自扩散系数，对先前论文中由密度涨落理论推导得出的剪切粘度公式，计算了氩气、氪气和甲烷的相关结果。在接近或高于临界温度的温度区间，如果将最小（临界）自由体积设定为分子体积，且在自扩散系数表达式中体积重叠参数（α）取值约为1，那么借助修正自由体积理论提供的自扩散系数，通过从头计算可以解释剪切粘度的密度依赖性。在亚临界温度区间，如果在某一温度下适当选取密度涨落范围参数，那么由此得到的剪切粘度表达式能够很好地解释在实验研究的密度和温度范围内其对密度和温度的依赖性。从某种意义上说，一旦在某一温度下确定了密度涨落范围，该理论仅基于分子间作用力就能解释其他亚临界温度下的实验数据；即便在亚临界温度区间，该理论也具有预测性。该理论与氩气、氪气和甲烷的自扩散系数及剪切粘度的实验数据对比，得到了成功验证。
