Molecular simulation of the shear viscosity and the self-diffusion coefficient of mercury along the vapor-liquid coexistence curve

Abstract

Prediction of self-diffusion coefficient and shear viscosity of water and its binary mixtures with methanol and ethanol by molecular simulation J. Chem. Phys. 134, 074508 (2011); 10.1063/1.3515262Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water modelIn earlier work ͓G. Raabe and R. J. Sadus, J. Chem. Phys. 119, 6691 ͑2003͔͒ we reported that the combination of an accurate two-body ab initio potential with an empirically determined multibody contribution enables the prediction of the phase coexistence properties, the heats of vaporization, and the pair distribution functions of mercury with reasonable accuracy. In this work we present molecular dynamics simulation results for the shear viscosity and self-diffusion coefficient of mercury along the vapor-liquid coexistence curve using our empirical effective potential. The comparison with experiment and calculations based on a modified Enskog theory shows that our multibody contribution yields reliable predictions of the self-diffusion coefficient at all densities. Good results are also obtained for the shear viscosity of mercury at low to moderate densities. Increasing deviations between the simulation and experimental viscosity data at high densities suggest that not only a temperature-dependent but also a density-dependent multibody contribution is necessary to account for the effect of intermolecular interactions in liquid metals. An analysis of our simulation data near the critical point yields a critical exponent of ␤ = 0.39, which is identical to the value obtained from the analysis of the experimental saturation densities.

Molecular dynamics simulation of potassium along the liquid-vapor coexistence curve

“…Therefore, the best results in this work are produced by employing an LJ (5-4) potential, which well reproduces the experimental PVT data for liquid and vapor phases up to temperatures as high as 2000 K, for which the experimental data are available [1]. Taking into account the nature of many-body interactions, like the method of Raabe and Sadus [9] and Raabe et al [10], may increase the accuracy of the results. We are currently contemplating a hypothesis on the basis of this assumption which is important enough to warrant experimentation.…”

“…It is should be mentioned that the density-dependent potential energy function by Kozhevnikov et al [12] obviously shows the temperature/density dependencies, which can be interpreted as a potential energy function with temperature-dependent parameters. Moreover, Raabe and Sadus [9] and Raabe et al [10] also introduced temperature-dependency in their treebody interactions for the sake of simulation of liquid mercury.…”

“…Additionally, this potential leads to freezing of liquid potassium at around 700 K. While there is a substantial error in predicting the freezing point of liquid potassium, the freezing point calculated using this potential is in a better agreement with experiment [1] compared to the predictions using LJ (12-6) potential, which predicts a freezing temperature of 900 K, and LJ (8.5-4) potential, which predicts a freezing temperature of 800 K. At this stage, our results show that taking into account the temperature-dependencies of LJ parameters and adjusting the magnitudes of attractive and repulsive forces play important roles in the accuracy of predictions. More accurate results can be obtained by introducing many-body interactions, like the method of Raabe and Sadus [9] and Raabe et al [10]. This point needs more clarification.…”

“…Recently, Raabe and Sadus [9] and Raabe et al [10] have shown that three body interactions are important in calculating the vapor-liquid coexistence curve of mercury. In addition, the results reported by Koshevnikov et al [12] show that liquid cesium obeys a simple LJ (8.5-4) potential energy function with pair-wise additive interactions.…”

“…This is even more complicated in the case of alkali metal vapors, as there are some contradictory reports in the literature. On the one hand, it is known that liquid metals do not obey pair-wise additive potentials [9][10][11]. On the other hand, some new reports on the development of equation of state for liquid alkali metals show the validity of a simple LJtype potential with pair-wise additive interactions [12][13][14].…”