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Influence of repulsion on modified entropy scaling and density scaling of monatomic fluids



Denis Saric, Ian Bell, Gabriela Fernanda Guevara Carrion, Jadran Vrabec


Modified entropy scaling is applied to shear viscosity, self-diffusion coefficient and thermal conductivity of fluids consisting of spherical molecules. 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 modified entropy scaling is applied. Hence, the 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 with literature data of n,6 Mie and exponential-six fluids. Further, 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 (or thermodynamic) scaling is applied for the transport properties of these potential model classes as well, revealing a strong influence of the repulsive exponent on this scaling approach.
Journal of Chemical Physics


Saric, D. , Bell, I. , Guevara Carrion, G. and Vrabec, J. (2024), Influence of repulsion on modified entropy scaling and density scaling of monatomic fluids, Journal of Chemical Physics, [online],, (Accessed July 14, 2024)


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Created March 8, 2024, Updated March 25, 2024