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Guillaume Galliero - One of the best experts on this subject based on the ideXlab platform.

  • Lennard-Jones Fluid-Fluid interfaces under shear
    Physical Review E : Statistical Nonlinear and Soft Matter Physics, 2010
    Co-Authors: Guillaume Galliero
    Abstract:

    Using nonequilibrium molecular dynamics simulations on simple Lennard-Jones binary mixtures, we have studied the behavior of planar Fluid-Fluid interfaces undergoing shear flow. When the miscibility is low enough, a slip together with a partial depletion have been noticed at the interface between the two Fluid phases. The slip length can reach a value equal to some molecular diameters and the corresponding interfacial viscosity can be two times smaller than the value in the bulk. It is shown how the omission of this slip may lead to flow-rate misevaluation when dealing with a multiphase flow in a nanoporous medium even for non polymer Fluids. In addition, using the simulation results, a simple relation between interfacial tension and interfacial viscosity is proposed for the monoatomic systems studied in this work. Finally, it is shown that the interfacial viscosity cannot be fully accounted for by estimating the local viscosity deduced from the local thermodynamic properties of the interface.

  • Thermal conductivity of the Lennard-Jones Fluid: an empirical correlation.
    Chemical Physics, 2008
    Co-Authors: Mathilde Bugel, Guillaume Galliero
    Abstract:

    In this work, is presented an empirical correlation on the thermal conductivity of the Lennard-Jones Fluid based on extensive non-equilibrium molecular dynamics simulations results (103 points). Finite size and cutoff radius effects are investigated and taken into account to develop the correlation. This last, composed of low density, residual and critical enhancement contributions, is built for a wide range of thermodynamics states, even at the vicinity of the critical point, and yields an average absolute deviation of 1.29 % compared to our simulations. In addition, a careful analysis of the different contributions to the microscopic flux is carried out which sheds light on the underlying mechanism of the results. Finally, are discussed the limitations of the proposed model when applied to real simple Fluids and mixtures using a standard corresponding states scheme and the van der Waals one-Fluid approximation.

  • Thermal conductivity of the Lennard-Jones Fluid: An empirical correlation
    Chemical Physics, 2008
    Co-Authors: Mathilde Bugel, Guillaume Galliero
    Abstract:

    International audienceIn this work, is presented an empirical correlation on the thermal conductivity of the Lennard-Jones Fluid based on extensive non-equilibrium molecular dynamics simulations results (103 points). Finite size and cutoff radius effects are investigated and taken into account to develop the correlation. This last, composed of low density, residual and critical enhancement contributions, is built for a wide range of thermodynamics states, even at the vicinity of the critical point, and yields an average absolute deviation of 1.29 % compared to our simulations. In addition, a careful analysis of the different contributions to the microscopic flux is carried out which sheds light on the underlying mechanism of the results. Finally, are discussed the limitations of the proposed model when applied to real simple Fluids and mixtures using a standard corresponding states scheme and the van der Waals one-Fluid approximation

  • Molecular dynamics study of the Lennard-Jones Fluid viscosity. Application to real Fluids
    Industrial and engineering chemistry research, 2005
    Co-Authors: Guillaume Galliero, Antoine Baylaucq, Christian Boned
    Abstract:

    A predictive scheme of viscosity for pure Fluids and mixtures of simple molecules is presented. First, using molecular dynamics data from the literature and also from our own study, a representative correlation of the viscosity of a Lennard-Jones Fluid is developed for a wide range of thermodynamic states. Second, a corresponding states scheme is proposed which allows the transposition of the previous results to real Fluids. For some simple molecules, this scheme induces deviations lower than 5% in conditions covering gas, liquid, and supercritical states. For larger molecules, the results are poorer but can be strongly improved by fitting the atomic diameter. Then, it is shown for simple binary and multicomponent mixtures that, by using merely a van der Waals one-Fluid approximation and the Lorentz-Berthelot rules, results are as good as for pure Fluids. Finally, the limitations of such a scheme are shown when applied on the methane + toluene asymmetric mixture.

Yiping Tang - One of the best experts on this subject based on the ideXlab platform.

  • OUTSIDE AND INSIDE THE CRITICAL REGION OF THE Lennard-Jones Fluid
    The Journal of Chemical Physics, 1998
    Co-Authors: Yiping Tang
    Abstract:

    The Lennard-Jones (LJ) Fluid is studied for states both inside and outside the critical region. Outside the critical region, the mean spherical approximation (MSA) theory is found best for calculating the phase diagram. Inside the critical region, the MSA yields the classical exponents as anticipated. The failure of the MSA and other mean field theories is resolved by a new renormalization group (RG) theory. The new theory is based on a combination of White’s RG transformation, the density functional theory, and the superposition approximation. The new RG theory reduces to White’s RG theory for the van der Waals equation of state and is applicable for other integral equation theories as well as the MSA. An implementation of the MSA+RG transformation for the LJ Fluid indicates that nonclassic behavior can be described satisfactorily. An accurate global theory is achieved in this work for the Lennard-Jones Fluid.

  • Analytical equation of state based on the Ornstein-Zernike equation
    Fluid Phase Equilibria, 1997
    Co-Authors: Yiping Tang, Zhangfa Tong
    Abstract:

    A new two-Yukawa function is found to mimic very closely the Lennard-Jones potential. Simple analytical expressions are developed for the structure and thermodynamic properties of the Lennard-Jones Fluid, utilizing the new function. The results from the expressions developed are satisfactorily compared with the Monte Carlo simulation data, the theory of Weeks et al. and the latest 33-parameter equation of state (EOS). The phase diagram of the Lennard-Jones Fluid is also well predicted by the new EOS. The properties of four real Fluids (argon, methane, oxygen and nitrogen) are calculated using the present EOS. Some noticeable improvements over the Peng-Robinson EOS are found for the calculation of saturated liquid densities and second virial coefficients.

  • First‐order radial distribution functions based on the mean spherical approximation for square‐well, Lennard‐Jones, and Kihara Fluids
    Journal of Chemical Physics, 1994
    Co-Authors: Yiping Tang, Benjamin C.‐y. Lu
    Abstract:

    Following the assumption of the mean spherical approximation, analytical expressions of the first‐order radial distribution function are obtained for the square‐well, Lennard‐Jones, and Kihara potentials with a hard core through a complex‐plane analysis. The developed expression yields good agreement with the available computer simulation data for the radial distribution function of the Lennard‐Jones Fluid.

Martin Lísal - One of the best experts on this subject based on the ideXlab platform.

  • Vapor-liquid equilibria of alternative refrigerants and their binaries by molecular simulations employing the reaction Gibbs ensemble Monte Carlo method
    Fluid Phase Equilibria, 2004
    Co-Authors: Robert Budinsky, Václav Vacek, Martin Lísal
    Abstract:

    Abstract Alternative refrigerants HFC125 (CHF2CF3) and HFC 134a (CF3CH2F) are modeled as a dipolar two-center Lennard–Jones Fluid and alternative refrigerant HFC32 (CH2F2) is modeled as a dipolar Lennard–Jones Fluid. We calculate vapor–liquid equilibria of these refrigerants by Gibbs–Duhem integration and vapor–liquid equilibria of two binaries (HFC 125 + HFC 134a and HFC 134a + HFC 32) by the reaction Gibbs ensemble Monte Carlo method. Potential parameters of the model are fitted to the critical temperature and vapor–liquid equilibrium data. The predictions are very good, and of comparable accuracy to those obtained using the Wilson and the UNIFAC thermodynamic-based approaches, even though such approaches use experimental mixture information.

  • Thermal properties of supercritical carbon dioxide by Monte Carlo simulations
    Molecular Simulation, 2003
    Co-Authors: Coray M. Colina, Claudio Olivera-fuentes, Martin Lísal, Flor R. Siperstein And, Keith E Gubbins
    Abstract:

    We present simulation results for the volume expansivity, isothermal compressibility, isobaric heat capacity, Joule-Thomson coefficient and speed of sound for carbon dioxide (CO 2 ) in the supercritical region, using the fluctuation method based on Monte Carlo simulations in the isothermal-isobaric ensemble. We model CO 2 as a quadrupolar two-center Lennard-Jones Fluid with potential parameters reported in the literature, derived from vapor-liquid equilibria (VLE) of CO 2 . We compare simulation results with an equation of state (EOS) for the two-center Lennard-Jones plus point quadrupole (2CLJQ) Fluid and with a multiparametric EOS adjusted to represent CO 2 experimental data. It is concluded that the VLE-based parameters used to model CO 2 as a quadrupolar two-center Lennard-Jones Fluid (both simulations and EOS) can be used with confidence for the prediction of thermodynamic properties, including those of industrial interest such as the speed of sound or Joule-Thomson coefficient, for CO 2 in the super...

  • Vapor–Liquid Equilibria of Alternative Refrigerants by Molecular Dynamics Simulations
    International Journal of Thermophysics, 1999
    Co-Authors: Martin Lísal, Robert Budinsky, Václav Vacek
    Abstract:

    Alternative refrigerants HFC-152a (CHF2CH3), HFC-143a (CF3CH3), HFC-134a (CF3CH2F), and HCFC-142b (CF2ClCH3) are modeled as a dipolar two-center Lennard–Jones Fluid. Potential parameters of the model are fitted to the critical temperature and vapor–liquid equilibrium data. The required vapor–liquid equilibrium data of the model Fluid are computed by the Gibbs–Duhem integration for molecular elongations L=0.505 and 0.67, and dipole moments μ*2=0, 2, 4, 5, 6, 7, and 8. Critical properties of the model Fluid are estimated from the law of rectilinear diameter and critical scaling relation. The vapor–liquid equilibrium data are represented by Wagner equations. Comparison of the vapor–liquid equilibrium data based on the dipolar two-center Lennard–Jones Fluid with data from the REFPROP database shows good-to-excellent agreement for coexisting densities and vapor pressure.

Swapan K. Ghosh - One of the best experts on this subject based on the ideXlab platform.

  • density functional theory of size dependent surface tension of lennard jones Fluid droplets using a double well type helmholtz free energy functional
    Journal of Chemical Physics, 2011
    Co-Authors: Satinath Ghosh, Swapan K. Ghosh
    Abstract:

    A double well type Helmholtz free energy density functional and a model density profile for a two phase vapor-liquid system are used to obtain the size-dependent interfacial properties of the vapor-liquid interface at coexistence condition along the lines of van der Waals and Cahn and Hilliard density functional formalism of the interface. The surface tension, temperature-density curve, density profile, and thickness of the interface of Lennard-Jones Fluid droplet-vapor equilibrium, as predicted in this work are reported. The planar interfacial properties, obtained from consideration of large radius of the liquid drop, are in good agreement with the results of other earlier theories and experiments. The same free energy model has been tested by solving the equations numerically, and the results compare well with those from the use of model density profile.

  • Integral equation theory of Lennard-Jones Fluids: A modified verlet bridge function approach
    The Journal of Chemical Physics, 2002
    Co-Authors: Niharendu Choudhury, Swapan K. Ghosh
    Abstract:

    An integral equation theory for the Lennard-Jones Fluid is investigated using a proposed new closure based on a modification of the Verlet-modified bridge function, which has been known to be very successful for hard body Fluids. The structural and thermodynamic properties of the Lennard-Jones Fluid calculated from this integral equation theory over a wide range of temperature and density show very good agreement with those obtained from simulation or from equation of state derived from simulation data. The gas–liquid phase diagram predicted by the present integral equation theory is shown to agree quite well with the corresponding simulation results.

Stanley I. Sandler - One of the best experts on this subject based on the ideXlab platform.

  • Equation of state for the Lennard–Jones Fluid based on the perturbation theory
    Fluid Phase Equilibria, 2007
    Co-Authors: Felix F. Betancourt-cárdenas, Luis A. Galicia-luna, Stanley I. Sandler
    Abstract:

    Abstract An easy-to-use equation of state for the Lennard–Jones Fluid based on the Barker and Henderson perturbation theory is presented. The model uses the hard sphere as the reference Fluid, with its properties described using the Carnahan–Starling equation of state and a shell approach to describe the radial distribution function. The contributions of first and second order terms in the perturbation series were calculated using molecular simulation and are compared with the proposed EoS. The equation presented is in good agreement with the molecular simulation data for the pressure and internal energy of the Lennard–Jones Fluid. As the equation is based on the perturbation theory it over predicts the critical temperature found from molecular simulation.

  • Phase diagram of the four-dimensional Lennard-Jones Fluid
    The Journal of Chemical Physics, 1999
    Co-Authors: M. Hloucha, Stanley I. Sandler
    Abstract:

    We have used the Gibbs ensemble Monte Carlo method to investigate Fluids in the N dimensional space. We consider the practical way to perform these simulations and give expressions for the long-range corrections. Results for the four-dimensional Lennard-Jones Fluid are presented. The calculated phase diagram and several thermodynamic properties for this Fluid are given. Estimates of the critical point and the critical exponent are obtained from the phase diagram. The simulations were performed with two different simulation techniques: random choice and a fixed sequence of Monte Carlo steps.

  • Equations of state from generalized perturbation theory: Part II. The Lennard-Jones Fluid
    Fluid Phase Equilibria, 1991
    Co-Authors: Gary M. Sowers, Stanley I. Sandler
    Abstract:

    Abstract Sowers, G.M. and Sandier, S.I., 1991. Equations of state from generalized perturbation theory. Part II. The Lennard-Jones Fluid. Fluid Phase Equilibria, 67: 127-150. We use perturbation theory to derive extensions of our equations of state used previously for the hard-core Lennard-Jones Fluid to the more realistic soft-core Lennard-Jones Fluid. We find that the use of a “hybrid” Barker-Henderson diameter (see Aim and Nezbeda, 1987) for the hard sphere reference Fluid leads to perturbation free energies for the soft-core Lennard- Jones Fluid that are similar to the perturbation free energies for a hard-core Lennard-Jones Fluid. For the range of temperatures and densities considered here, one of our equations of state is more accurate than a 33-parameter equation (see Adachi et al., 1988) even though it has only four adjustable parameters. The other equation of state is a straightforward, theoretically based extension of a square-well equation of state (see Lee et al., 1985) to the Lennard-Jones Fluid. Both equations of state can be used to correlate the phase diagrams and supercritical PVT data of noble gases and methane, and perform especially well in the correlation of saturated liquid volumes.