scholarly journals Vapor-liquid interfacial properties of the system cyclohexane + CO2: Experiments, molecular simulation and density gradient theory

2021 ◽  
Author(s):  
Simon Stephan ◽  
Stefan Becker ◽  
Kai Langenbach ◽  
Hans Hasse
Keyword(s):  
Density Gradient ◽  
Md Simulation ◽  
Interfacial Properties ◽  
Gradient Theory ◽  
Pendant Drop ◽  
Pure Substances ◽  
Density Gradient Theory ◽  
Relative Adsorption ◽  
Good Agreement ◽  
Vapor Liquid

Properties of the vapor-liquid interface of the binary mixture cyclohexane + CO2 as well as for the two pure substances are reported. The data were obtained from pendant drop experiments (Exp), molecular dynamics (MD) simulation, and density gradient theory (DGT) in combination with the PCP-SAFT equation of state. The following interfacial properties were studied: surface tension (Exp, MD, DGT), relative adsorption (Exp, MD, DGT), enrichment (MD, DGT), and interfacial thickness (MD, DGT). The measurements were carried out at temperatures between 303.15 K and 373.15 K and pressures up to 6 MPa. Furthermore, bulk VLE properties were computed by MD and PCP-SAFT and compared to experimental data from the literature. Data from experiment, MD, and DGT were found to be in good agreement throughout.

scholarly journals Interfacial Properties of Binary Lennard-Jones Mixtures by Molecular Simulation and Density Gradient Theory

2021 ◽  
Author(s):  
Simon Stephan ◽  
Kai Langenbach ◽  
Hans Hasse
Keyword(s):  
Density Gradient ◽  
Binary Mixtures ◽  
Md Simulation ◽  
Interfacial Properties ◽  
Gradient Theory ◽  
Combination Rule ◽  
Lennard Jones ◽  
High Boiling Point ◽  
Density Gradient Theory ◽  
Relative Adsorption

A systematic study of interfacial properties of binary mixtures of simpleuids wascarried out by molecular dynamics (MD) simulation and density gradient theory(DGT). Theuids are described by the Lennard-Jones truncated and shifted potentialwith truncation radius of 2.5 diameters (LJTSuid). The following interfacialproperties were studied: surface tension, relative adsorption, enrichment, and interfacialthickness. A recently developed equation of state for the LJTSuid (PeTS EOS)was used as basis for the DGT. Six binary mixtures (components 1 + 2) were studiedat a constant temperature, which was chosen such that the high-boiling component1 is subcritical while the low-boiling component 2 is either subcritical or supercritical.Furthermore, a parameter ? in the combination rule for the unlike dispersiveinteraction was varied such that the resulting mixtures showed three types of behavior:high-boiling azeotrope, ideal, and low-boiling azeotrope. The parametersof the LJTS potential, including ?, were also used in the PeTS EOS without anyadjustment. Despite this simple approach, excellent agreement between the resultsof the PeTS EOS and the MD results for the phase equilibrium and the interfacialproperties is observed. Enrichment at the interface is only found for the low-boilingcomponent 2. The enrichment increases with decreasing concentration of component2 and is favored by high boiling point di?erences of the pure components 1 and 2 andpositive deviations from Raoult's law for the mixture 1 + 2.

Modelling interfacial properties of ionic liquids with ePC-SAFT combined with density gradient theory

2016 ◽  
Vol 114 (16-17) ◽  
pp. 2492-2499 ◽  
Author(s):  
Gulou Shen ◽  
Christoph Held ◽  
Xiaohua Lu ◽  
Xiaoyan Ji
Keyword(s):  
Ionic Liquids ◽  
Density Gradient ◽  
Interfacial Properties ◽  
Gradient Theory ◽  
Density Gradient Theory

scholarly journals Vapor−Liquid Interface of the Lennard-Jones Truncated and Shifted Fluid: Comparison of Molecular Simulation, Density Gradient Theory, and Density Functional Theory

2021 ◽  
Author(s):  
Simon Stephan ◽  
Jinlu Liu ◽  
Kai Langenbach ◽  
Walter G. Chapman ◽  
Hans Hasse
Keyword(s):  
Density Functional Theory ◽  
Density Gradient ◽  
Density Functional ◽  
Computer Experiments ◽  
Liquid Interface ◽  
Gradient Theory ◽  
Functional Theory ◽  
Lennard Jones ◽  
Density Gradient Theory ◽  
Vapor Liquid

The vapor-liquid interface of the Lennard-Jones truncated and shifted (LTJS) fluid with a cut-off radius of 2.5 σ is investigated for temperatures covering the range between the triple point and the critical point. Three different approaches to model the vapor-liquid interface are used: molecular dynamics (MD) simulations, density gradient theory (DGT) and density functional theory (DFT). The surface tension, pressure and density profiles, including the oscillatory layering structure of the fluid at the interface, are investigated. The PeTS (Perturbed truncated and shifted) equation of state and PeTS-i functional, based on perturbation theory, are used to calculate the Helmholtz free energy in the DGT and DFT approach. They are consistent with the LJTS force field model. Overall, both DGT and DFT describe the results from computer experiments well. An oscillatory layering structure is found in MD and DFT.

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