Showing papers by "Johann Fischer published in 1989"
TL;DR: Etude, par des simulations de dynamique moleculaire, de l'ecoulement de Hayen-Poiseuille d'un liquide de Lennard Jones a travers un pore cylindrique forme par un arrangement regulier d'atomes fixes.
Abstract: The Hagen-Poiseuille flow of a Lennard-Jones liquid through a cylindrical pore formed by regularly arranged fixed atoms is studied by molecular-dynamics (MD) simulations. Different flow patterns develop depending on the strength of the wall-fluid interaction, the strength of the gravitational-type driving force, the thermodynamic state, and also on the mechanism of heat dissipation. In spite of the high driving forces necessary in MD it is found that up to two molecular layers may stick at the wall which confirms recent experimental findings.
153 citations
TL;DR: In this article, the new refrigerant R152a (CH3-CHF2) is modelled as a fluid of homonuclear two-centre Lennard-Jones molecules with a point dipole along the axis.
Abstract: The new refrigerant R152a (CH3-CHF2) is modelled as a fluid of homonuclear two-centre Lennard-Jones molecules with a point dipole along the axis. This 2CLJD potential has four parameters which were determined by using results of previous and new molecular dynamics simulations for 2CLJD molecules of elongation L* = 0·505 and different reduced dipole moments μ*. For each of these dipole moments zero pressure liquid densities at two temperatures were taken to determine the Lennard-Jones parameters ϵ and σ from a fit to experimental saturated liquid densities. A subsequent comparison of calculated second virial coefficients with experimental values led to the conclusion that μ*2 = 8 in combination with ϵ/k = 119·0K and σ = 3.845 A is a reasonable choice. Further simulations with those parameters, all performed with vectorized codes on a CYBER 205, gave reasonable predictions of the thermodynamic properties. As the reduced dipole moment μ*2 = 8 corresponds to 2·73 D compared to the experimental value of 2·27 D...
55 citations
TL;DR: In this paper, Widom's test particle method is applied in combination with molecular dynamics simulations using vectorized codes on a CYBER 205 to check the results at infinite dilution of component A, and two consistency tests are given.
Abstract: The calculation of chemical potentials from a WCA-type perturbation theory (PT) is described and two consistency tests are given. To check the results at infinite dilution of component A, Widom's test particle method is applied in combination with molecular dynamics (MD) simulations using vectorized codes on a CYBER 205. Technically, with increasing size of the test particles firstly the test particle cut-off radius and secondly the number of time steps has to be increased. Comparison of PT with MD results shows good agreement especially for σ AB /σ BB < 1 and e AB /e BB < 1 which is the parameter region for the solubility of gases (A) in liquids (B). The agreement is least satisfactory for decreasing σ AB /σ BB while simultaneously increasing e AB /e BB which is a typical ‘local composition’ effect for which PT does not account. Comparison with the results of Shing and Gubbins 1982, [Molec. Phys., 46, 1109] shows, however, discrepancies in some cases. Finally, predictions of Henry's constants for the mix...
41 citations
TL;DR: In this paper, an extension of the density functional theory for singlet distribution function of a fluid in contact with a solid by taking into account triple coupling function is proposed. But the results obtained are compared with the previous theoretical predictions and with results of Monte Carlo simulations, performed on Cyber 205 supercomputer.
Abstract: Using the method developed by Meister and Kroll (1985, Phys. Rev. A, 31, 4055), we have proposed an extension of the density functional theory for singlet distribution function of a fluid in contact with a solid by taking into account triple coupling function. The proposed equation is then solved numerically for hard spheres in contact with a hard wall and with a soft wall interacting through a Lennard-Jones (9, 3) potential and the results obtained are compared with the previous theoretical predictions and with results of Monte Carlo simulations, performed on Cyber 205 supercomputer. The numerical calculations indicate that the inclusion of the third-order term improves the accuracy of the density functional calculations.
29 citations
TL;DR: The Born-Green-Yvon approach using a coarse grained density was applied to study the adsorption of a subcritical Lennard-Jones fluid as discussed by the authors, and the results showed that at low temperature the gas forms only one layer in approaching the vapour pressure.
Abstract: The Born-Green-Yvon approach using a coarse grained density is applied to study the adsorption of a subcritical Lennard-Jones fluid. In case of a strongly adsorbing wall the adsorbed gas forms several layers with increasing pressure. Close to the vapour pressure the layers are followed by a film of nearly saturated liquid density the thickness of which increases rapidly. At low temperature the layer formation occurs rather suddenly causing type VI (multistepped) adsorption isotherms whilst at high temperature type II (concave one-step BET) adsorption isotherms are obtained. The adsorbed liquid shows the same layered structure as the gas. In case of a weakly adsorbing wall the adsorption mechanism close to saturation at high temperature is similar to that at a strongly adsorbing wall; comparison with the results from the density functional theory of Meister and Kroll is made. At low temperature, however, the gas forms only one layer in approaching the vapour pressure. For all temperatures the adsorption is...
24 citations
TL;DR: In this paper, the dependence of the liquid mixture excess properties g E, h E, and v E on an unlike molecule interaction parameter is considered and the derivatives of the excess properties with respect to that parameter are expressed as averages in the isobaric-isothermal (NpT) ensemble which can be evaluated in computer simulations.
21 citations
TL;DR: In this article, the Born-Green-Yvon approach of Fischer and Methfessel is extended to binary mixtures of equally sized molecules, and two model mixtures are considered in contact with a plane, strongly adsorbing 9 3 wall.
17 citations
TL;DR: In this article, the differences between the excess Gibbs free energy for mixing at constant pressure and the excess Helmholtz free energies for mixing subject to other constraints are considered, and the difference may be an order of magnitude larger than the excess GFE.
6 citations
TL;DR: In this article, it is shown that starting from FLB theory but neglecting the unlike blip term produces a version of perturbation theory that is unsatisfactory for large deviations from the Lorentz-Berthelot rules.
4 citations
TL;DR: In this article, the consolute curve for the mixture CH 4 CF 4 at zero pressure is predicted using two mixture models, one modelling both components as spheres, the other modelling CH 4 as a sphere and CF 4 as tetrahedron.
3 citations
TL;DR: In this article, it is argued that these shape effects can roughly be incorporated into the kAB-parameter, which then for molecules not too different in size will be negative.