Influence of the repulsive force potential exponent on viscous and elastic properties of Lennard-Jones fluids

Adamenko, I. I.; Grigoriev, A.N.; Kuzovkov, Yu.I.

doi:10.1016/s0167-7322(03)00064-3

Cited by 9 publications

(5 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…53 To circumvent these relatively weak results in a very dense phase, keeping a spherical approximation, a different choice in the way to describe the repulsive part of the potential, with a different repulsive exponent or an exponential description, may be a valuable alternative. [54][55][56] But, more simply, a fit of the molecular parameters using the viscosity database will certainly improve results compared to a purely predictive scheme. Such work to construct a viscosity-optimized database of molecular parameters is in progress.…”

Section: Numerical Results For Real Fluidsmentioning

confidence: 99%

“…Concerning the large deviations at very high pressure on quasi-spherical molecules (see methane or argon, Figures and , respectively), it is probably due to the simple repulsive form of the LJ potential, which is not accurate enough in extreme pressure cases . To circumvent these relatively weak results in a very dense phase, keeping a spherical approximation, a different choice in the way to describe the repulsive part of the potential, with a different repulsive exponent or an exponential description, may be a valuable alternative. − But, more simply, a fit of the molecular parameters using the viscosity database will certainly improve results compared to a purely predictive scheme. Such work to construct a viscosity-optimized database of molecular parameters is in progress.…”

Section: Numerical Results For Real Fluidsmentioning

confidence: 99%

See 1 more Smart Citation

Molecular Dynamics Study of the Lennard−Jones Fluid Viscosity: Application to Real Fluids

Galliéro

Boned

Baylaucq

2005

Ind. Eng. Chem. Res.

142

126

View full text Add to dashboard Cite

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.

show abstract

Section: Numerical Results For Real Fluidsmentioning

confidence: 99%

Section: Numerical Results For Real Fluidsmentioning

confidence: 99%

Molecular Dynamics Study of the Lennard−Jones Fluid Viscosity: Application to Real Fluids

Galliéro

Boned

Baylaucq

2005

Ind. Eng. Chem. Res.

142

126

View full text Add to dashboard Cite

show abstract

“…In this context, the effective two parameter Lennard-Jones ͑LJ͒ 12-6 potential is the most widely used model for exploring the behavior of simple fluids ͑i.e., molecules for which the most important intermolecular forces are repulsion and van der Waals disper-sion͒ in statistical physics and related scientific domains. [5][6][7][8][9][10] Apart from their direct use in molecular simulations, simple effective potentials can be used as the elementary bricks of modern molecular-based equation of state ͑EOS͒. However, from a theoretical point of view, it is well known that the LJ potential is not a true representation of even two-body interactions between argon atoms.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic properties of the Mie n-6 fluid: A comparison between statistical associating fluid theory of variable range approach and molecular dynamics results

Galliéro

Lafitte

Bessières

et al. 2007

The Journal of Chemical Physics

View full text Add to dashboard Cite

Molecular dynamics (MD) simulations of direct and derivative thermodynamic properties of the Mie n-6 fluid (n=8, 10, and 12) have been performed for liquid to supercritical states. Using the results, an in depth test of the monomer-monomer interaction estimation of a recently derived statistical associating fluid theory of variable range (SAFT-VR) equation of state [Lafitte et al., J. Chem. Phys., 124, 024509 (2006)] has been carried out based on the Mie n-6 potential. For pure fluids, using an appropriate scaling, MD simulations show that density and isometric heat capacity are nearly independent of n, whereas sound velocity and thermal pressure coefficient tend to increase with n. In addition, the results show that predictions provided by the equation of state are consistent with those coming from MD and catch correctly the trends of each property with n except for the heat capacity. The comparison is next extended to binary mixtures with components differing only in the value of the n parameter and which demonstrate the reliability of the scheme (MX1b) used by Lafitte et al. to deal with this parameter in the SAFT-VR equation of state. In addition, a new empirical one-fluid approximation of the n parameter is proposed thanks to MD simulations, which very favorably compare with the one-fluid model on n previously proposed in the literature. The consistency of this approximation is addressed by making use of it in combination with the SAFT-VR Mie equation of state. It is shown that using such an approach, which is easier to handle than the MX1b one, yields slightly improved results compared to those of the MX1b.

show abstract

“…The IPL approximation emphasizes the dominant role of the short-range repulsive interactions for local properties such as structural relaxation. Various groups have explored through numerical simulations the relationship of the steepness of the repulsive potential to properties such as the equation of state, − longitudinal wave transmission, vibrational spectrum, liquid and gaseous transport, the correlation between fluctuations of energy and pressure, and the fragility. , Recently, two simulations have appeared in which eq 1 was used to superpose dynamical data for polymer chains described using an LJ m −6 potential with m = 12 and an added term for the intrachain interactions. The results appear contradictory: Tsolou et al obtained a scaling exponent of γ = 2.8 for the segmental relaxation times of simulated 1,4-polybutadiene, while Budzien et al superposed diffusion coefficients for prototypical polymer chains using γ = 6 when attractions were included in the simulation and γ = 12 when they were omitted.…”

mentioning

confidence: 99%

Thermodynamic Scaling of Diffusion in Supercooled Lennard-Jones Liquids

2008

View full text Add to dashboard Cite

The manner in which the intermolecular potential u(r) governs structural relaxation in liquids is a long standing problem in condensed matter physics. Herein, we show, in agreement with recent experimental results, that diffusion coefficients for simulated Lennard-Jones m-6 liquids (8 e m e 36) in normal and moderately supercooled states are a unique function of the variable F γ /T, where F is density and T is temperature. The scaling exponent γ is a material specific constant whose magnitude is related to the steepness of the repulsive part of u(r), evaluated around the distance of closest approach between particles probed in the supercooled regime. Approximations of u(r) in terms of inverse power laws are also discussed.Establishing a quantitative connection between the relaxation properties of a liquid and the interactions among its constituent molecules is the sine qua non for fundamental understanding and prediction of the dynamical properties. The supercooled regime is of particular interest, since both intermolecular forces and steric constraints (excluded volume) exert significant effects on the dynamics. This makes temperature, pressure, and volume essential experimental variables to characterize the relaxation properties. One successful approach to at least categorize dynamic properties of supercooled liquids and polymers is by expressing them as a function of the ratio of mass density F to temperature T, with the former raised to a material specific constant γ, namely, where x is the dynamic quantity under consideration, such as the structural relaxation time τ, the viscosity η, or the diffusion coefficient D, and F is a function. This scaling was first applied to a Lennard-Jones (LJ) fluid, with γ ) 4 yielding approximate master curves of the reduced "excess" viscosity for different thermodynamic conditions. 1 More recently, eq 1 has been shown to superpose relaxation times measured by neutron scattering, 2 light scattering, 3 viscosity, 4 and dielectric spectroscopy 5-9 for a broad range of materials, including polymer blends and ionic liquids. The scaling exponent γ, which varies in the range from 0.13 to 8.5, 10 is a measure of the contribution of density (or volume) to the dynamics, relative to that due to temperature. The only breakdown of the scaling is observed for hydrogenbonded liquids, in which the concentration of H-bonds changes with T and P, causing τ to deviate from eq 1. 4

show abstract

Influence of the repulsive force potential exponent on viscous and elastic properties of Lennard-Jones fluids

Cited by 9 publications

References 2 publications

Molecular Dynamics Study of the Lennard−Jones Fluid Viscosity: Application to Real Fluids

Molecular Dynamics Study of the Lennard−Jones Fluid Viscosity: Application to Real Fluids

Thermodynamic properties of the Mie n-6 fluid: A comparison between statistical associating fluid theory of variable range approach and molecular dynamics results

Thermodynamic Scaling of Diffusion in Supercooled Lennard-Jones Liquids

Contact Info

Product

Resources

About