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 D₁₁. 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 D₁₁ approaching T_c, despite excellent agreement between simulations and reference data for neat ethane.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ethane
• molecular dynamics simulations
• critical phenomena
• diffusion

Acknowledgment

This work was financially supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) via the project Grants FR 1709/11-1 and FR 1709/11-2. The authors gratefully acknowledge funding of the Erlangen Graduate School in Advanced Optical Technologies (SAOT) by the Bavarian State Ministry for Science and Art and further gratefully acknowledge the computing resources and support provided by the Erlangen Regional Computing Center (RRZE).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Deutsche Forschungsgemeinschaft: [Grant Numbers FR 1709/11-1 and FR 1709/11-2].