Saric Denis, Bell Ian H, Guevara-Carrion Gabriela, Vrabec Jadran
Thermodynamics, Technical University of Berlin, Ernst-Reuter-Platz 1, 10587 Berlin, Germany.
Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
J Chem Phys. 2024 Mar 14;160(10). doi: 10.1063/5.0196592.
Entropy scaling is applied to the shear viscosity, self-diffusion coefficient, and thermal conductivity of simple monatomic fluids. An extensive molecular dynamics simulation series is performed to obtain these transport properties and the residual entropy of three potential model classes with variable repulsive exponents: n, 6 Mie (n = 9, 12, 15, and 18), Buckingham's exponential-six (α = 12, 14, 18, and 30), and Tang-Toennies (αT = 4.051, 4.275, and 4.600). A wide range of liquid and supercritical gas- and liquid-like states is covered with a total of 1120 state points. Comparisons to equations of state, literature data, and transport property correlations are made. Although the absolute transport property values within a given potential model class may strongly depend on the repulsive exponent, it is found that the repulsive steepness plays a negligible role when entropy scaling is applied. Hence, the plus-scaled transport properties of n, 6 Mie, exponential-six, and Tang-Toennies fluids lie basically on one master curve, which closely corresponds with entropy scaling correlations for the Lennard-Jones fluid. This trend is confirmed by literature data of n, 6 Mie, and exponential-six fluids. Furthermore, entropy scaling holds for state points where the Pearson correlation coefficient R is well below 0.9. The condition R > 0.9 for strongly correlating liquids is thus not necessary for the successful application of entropy scaling, pointing out that isomorph theory may be a part of a more general framework that is behind the success of entropy scaling. Density scaling reveals a strong influence of the repulsive exponent on this particular approach.
熵标度被应用于简单单原子流体的剪切粘度、自扩散系数和热导率。进行了一系列广泛的分子动力学模拟，以获得这些输运性质以及具有可变排斥指数的三类势模型的残余熵：n, 6米氏势（n = 9、12、15和18）、白金汉指数六势（α = 12、14、18和30）以及唐-托尼斯势（αT = 4.051、4.275和4.600）。总共1120个状态点覆盖了广泛的液体以及超临界气态和类液态状态。与状态方程、文献数据以及输运性质关联进行了比较。尽管在给定的势模型类别中，绝对输运性质值可能强烈依赖于排斥指数，但发现当应用熵标度时，排斥陡度起的作用可忽略不计。因此，n, 6米氏势、指数六势和唐-托尼斯势流体的加标度输运性质基本位于一条主曲线上，这与 Lennard-Jones 流体的熵标度关联密切对应。n, 6米氏势和指数六势流体的文献数据证实了这一趋势。此外，对于皮尔逊相关系数R远低于0.9的状态点，熵标度仍然成立。因此，对于强相关液体R > 0.9这一条件对于熵标度的成功应用并非必要，这表明同构理论可能是熵标度成功背后更一般框架的一部分。密度标度揭示了排斥指数对这种特定方法有很大影响。
