A systematic study of interfacial properties of binary mixtures of simple fluids was carried out by molecular dynamics (MD) simulation and density gradient theory (DGT). The fluids are described by the Lennard-Jones truncated and shifted (LJTS) potential with truncation radius of 2.5 diameters. The following interfacial properties were studied: surface tension, relative adsorption, enrichment, and interfacial thickness. A recently developed equation of state for the LJTS fluid, the Perturbed Lennard-Jones truncated and shifted equation of state (PeTS EOS) was used as the basis for DGT. Six binary mixtures (components 1 + 2) were studied at a constant temperature, which was chosen such that the high-boiling component 1 is subcritical, while the low-boiling component 2 is either subcritical or supercritical. Furthermore, a parameter ξ in the combination rule for the unlike dispersive interaction was varied such that the resulting mixtures showed three types of behavior: high-boiling azeotrope, ideal, and low-boiling azeotrope. The parameters of the LJTS potential, including ξ, were also used in the PeTS EOS without any adjustment. Despite this simple approach, excellent agreement between the results of the PeTS EOS and the MD results for the phase equilibrium and the interfacial properties is observed. Enrichment at the interface is only found for the low-boiling component 2. The enrichment increases with decreasing concentration of component 2 and is favored by high boiling point differences of the pure components 1 and 2 and positive deviations from Raoult’s law for the mixture 1 + 2.
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7 May 2019
Research Article|
May 03 2019
Interfacial properties of binary Lennard-Jones mixtures by molecular simulation and density gradient theory
Simon Stephan;
Simon Stephan
Laboratory of Engineering Thermodynamics (LTD), TU Kaiserslautern
, Kaiserslautern, Germany
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Kai Langenbach
;
Kai Langenbach
a)
Laboratory of Engineering Thermodynamics (LTD), TU Kaiserslautern
, Kaiserslautern, Germany
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Hans Hasse
Hans Hasse
Laboratory of Engineering Thermodynamics (LTD), TU Kaiserslautern
, Kaiserslautern, Germany
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a)
Electronic mail: Kai.Langenbach@mv.uni-kl.de
J. Chem. Phys. 150, 174704 (2019)
Article history
Received:
February 22 2019
Accepted:
April 04 2019
Citation
Simon Stephan, Kai Langenbach, Hans Hasse; Interfacial properties of binary Lennard-Jones mixtures by molecular simulation and density gradient theory. J. Chem. Phys. 7 May 2019; 150 (17): 174704. https://doi.org/10.1063/1.5093603
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