Molecular dynamics simulations of liquid ethane up to 298.15 K

Abstract

Equilibrium molecular dynamics (EMD) simulations are used to model density ρ L, dynamic viscosity η L, and self-diffusivity D self of liquid ethane at pressures close to saturation conditions and temperatures T between (184–298) K, close to the critical temperature T c. To correct for a T-dependent drift of the simulated results from experimental data, a T-dependent force field modification from our previous studies is extended to a wider T-range. The modification is validated within this work by comparing predicted ρ L, η L, and D self to experimental reference data. With the modification applied, EMD simulations are able to predict ρ L, η L, and D self of liquid ethane at T = 298 K with relative deviations of 6.3%, 13%, and 28% from literature references, respectively. Simulations of binary mixtures of liquid ethane with different dissolved gases were performed to predict the Fick diffusivity D 11. At a mole fraction of dissolved nitrogen x N2 = 0.03, a deviation of more than a factor of three is found between simulation results and experimental results determined using the dynamic light scattering method. This shows that EMD simulations are not able to predict the critical slowing down of D 11 approaching T c, despite excellent agreement between simulations and reference data for neat ethane.