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

  • Thermal Diffusion in lennard jones fluids in the frame of the law of the corresponding states
    Fluid Phase Equilibria, 2004
    Co-Authors: Guillaume Galliero
    Abstract:

    Abstract This work is related to the definition of a reduced Thermal Diffusion coefficient thanks to numerical microscale molecular dynamics simulations. This cross transport process, also called Soret effect, couples mass flux and Thermal gradient and is still largely misunderstood. For this study, we have applied a boundary driven non-equilibrium molecular dynamics algorithm on Lennard–Jones spheres mixtures. Simulations have been performed at a constant reduced supercritical state, using a van der Waals’ one fluid approximation in order to fulfil the law of the corresponding states. In binary mixtures, we have studied the molecular parameters and the molar fraction influences on Thermal Diffusion separately and then combined. It is shown that, on pressure and on Thermal conductivity, the corresponding states law is fulfilled for a wide range of molecular parameters ratios. In this frame, we have then constructed simple correlations which relate Thermal Diffusion Factor to the mixture parameters. Combining the relations obtained, a reduced Thermal Diffusion Factor taking into account all the various contributions has been defined. Finally, it is shown that this relation enables us to estimate Thermal Diffusion in various binary and ternary mixtures of Lennard–Jones spheres representing alkanes with a maximum deviation of 15%.

Saeed Yeganegi - One of the best experts on this subject based on the ideXlab platform.

  • Thermal Diffusion Factor of binary mixtures of square well fluids
    Journal of the Physical Society of Japan, 2008
    Co-Authors: Saeed Yeganegi, Azita Amoozad Khalili, Mahshid Hamzehlooian
    Abstract:

    In this work we have performed HEX-NEMD simulations to calculate Thermal Diffusion Factor (TDF) for binary mixtures of square well particles for a wide range of diameter ratios, well depth ratios and well width ratios for a fixed reduced density and temperature. The results show that dependence of TDF to the potential parameters is resembled to the Lennard-Jonnes mixtures. The TDF decreases with diameter ratio. However, TDF increases as the ratios of well depth, well width and mass of two particles become larger than one.

  • comparison of efficiency equilibrium and non equilibrium molecular dynamics calculations of Thermal Diffusion Factor
    Journal of the Physical Society of Japan, 2007
    Co-Authors: Saeed Yeganegi, Mojdeh Anbarfam
    Abstract:

    The performance of the equilibrium and direct nonequilibrium simulation methods for the calculation of Thermal Diffusion are examined. Both methods show size dependency for particle number less than 500. The equilibrium simulation should perform for at least 48 ns to obtain statistical errors less than 5%. For a same particle number and simulation length the direct nonequilibrium simulation is one order of magnitude more accurate than the equilibrium one.

  • non equilibrium molecular dynamics calculation of Thermal Diffusion Factor in binary mixtures of hard spheres
    Fluid Phase Equilibria, 2006
    Co-Authors: Saeed Yeganegi, Mahdieh Zolfaghari
    Abstract:

    The Thermal Diffusion Factor for binary mixtures of hard spheres was calculated by a direct non-equilibrium molecular dynamics simulation method. The results obtained showed that for equimolar isotopic binary mixtures of hard spheres, the Thermal Diffusion Factor (TDF) increases with density at fixed mass ratios and increases with mass ratio at fixed packing fractions. The dependence of TDF on diameter ratio was also investigated and it was found that if the mass ratio is equal to 1 then larger species are accumulated in the warm region. The reciprocal of the Thermal Diffusion Factor as a function of the mole fraction of the heavier component in two packing fractions was studied as well. The results obtained showed that inverse of Thermal Diffusion Factor 1/TDF tends to be more linear when the mass ratio significantly differ from 1 and the diameter ratio is close to 1. These results are in good agreement with revised Enskog theory (RET). It was also found that those low density results continue to apply at higher densities too.

  • dependence of Thermal Diffusion Factor of binary mixtures to the thermodynamic state by nemd simulation
    Principles and Practice of Constraint Programming, 2005
    Co-Authors: Saeed Yeganegi, Masoud Darvish Ganji
    Abstract:

    Abstract In this paper, we investigate the dependence of Thermal Diffusion Factor and Thermal conductivity to the temperature, density and mole fraction in Lennard–Jones binary mixtures of isotopes, noble gases and SF 6 –noble gases by non-equilibrium molecular dynamics simulations. The results for the isotopic mixtures indicated that the density has a crucial effect on the dependence of Thermal Diffusion Factor on the temperature. For isotope system at low density, Thermal Diffusion Factor increased with temperature then remains constant at higher temperatures and the slope of Thermal Diffusion Factor vs. temperature is positive while at higher density, Thermal Diffusion Factor decreased with temperature and then fluctuate. For noble gas mixtures, Thermal Diffusion Factor reduces with increasing of temperature and remain constant at high temperatures. For SF 6 –Ar system, Thermal Diffusion Factor has a negative slope and reduced with increasing of temperature, but remain nearly constant at high temperatures. For Xe–SF 6 Thermal Diffusion Factor changed sign and the slope of Thermal Diffusion Factor vs. temperature was negative. The results also show that Thermal conductivity increases with temperature for all systems. The dependence of Thermal Diffusion Factor to mole fraction of heavier component also investigated. The inverse of Thermal Diffusion Factor versus mole fraction of heavier component is linear for isotope mixtures at thermodynamic conditions: (a) Low temperature, large mass ratio and all densities. (b) High temperature, large mass ratio and low densities. For Ne–Kr mixture, the inverse of Thermal Diffusion Factor shows a linear dependence to the mole fraction of heavier component in moderate temperatures and all densities. For SF 6 –Ar and Xe–SF 6 mixtures, the inverse of Thermal Diffusion Factor has linear behaviour at moderate temperatures and low density and high temperature and low density, respectively.

  • temperature dependence of Thermal Diffusion Factor for isotopic binary mixtures by non equilibrium molecular dynamics simulation
    Journal of the Physical Society of Japan, 2003
    Co-Authors: Saeed Yeganegi
    Abstract:

    We have studied the dependence of Thermal Diffusion Factor to the temperature for supercritical dense equimolar isotopic binary mixtures of atoms by direct Nonequilibrium molecular dynamics simulation method. The results showed that for these systems the sign of Thermal Diffusion Factor and slope of it with respect to the temperature is positive. For low mass ratio the variation of Thermal Diffusion Factor with temperature is very slow, and for higher mass ratio Thermal Diffusion Factor increases with temperature. Based on the ratios of components of energy flux, microscopic mechanisms of energy transfer across the system are also analyzed.

Muhammad Shadman - One of the best experts on this subject based on the ideXlab platform.

Bjørn Hafskjold - One of the best experts on this subject based on the ideXlab platform.

  • Nonequilibrium molecular dynamics calculation of the Thermal Diffusion Factor
    Fluid Phase Equilibria, 1992
    Co-Authors: Jordan M Kincaid, Bjørn Hafskjold
    Abstract:

    A nonequilibrium molecular dynamics method that allows direct calculation of the Thermal Diffusion Factor, α, is presented. Using boundary conditions to establish a temperature gradient between two opposing faces of a cubic volume, a steady state is achieved in which the temperature and composition fields are spatially nonuniform. The Thermal Diffusion Factor is obtained from observations of the temperature, composition and their gradients. We report calculations of α for a binary (isotopic) mixture of particles that interact with a (12-6) Lennard-Jones potential that is modified so that the interparticle force tends smoothly to zero at a finite range; supercritical systems of 108,256,500, and 1372 particles at a moderate fluid density are examined in which the particle mass ratios are 2, 5, and 10. We find that the dependence of α on the mass ratio (at fixed density, composition, and temperature) is similar to that observed in the Enskog theory for hard spheres. © 1992.

Xiaopo Wang - One of the best experts on this subject based on the ideXlab platform.

  • accurate ab initio potential for the krypton dimer and transport properties of the low density krypton gas
    Journal of Chemical Physics, 2015
    Co-Authors: Jonathan M Waldrop, Bo Song, Konrad Patkowski, Xiaopo Wang
    Abstract:

    A new highly accurate potential energy curve for the krypton dimer was constructed using coupled-cluster calculations up to the singles, doubles, triples, and perturbative quadruples level, including corrections for core-core and core-valence correlation and for relativistic effects. The ab initio data points were fitted to an analytic potential which was used to compute the most important transport properties of the krypton gas. The viscosity, Thermal conductivity, self-Diffusion coefficient, and Thermal Diffusion Factor were calculated by the kinetic theory at low density and temperatures from 116 to 5000 K. The comparisons with literature experimental data as well as with values from other pair potentials indicate that our new potential is superior to all previous ones. The transport property values computed in this work are recommended as standard values over the complete temperature range.