The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform

Jadran Vrabec - One of the best experts on this subject based on the ideXlab platform.

  • Premelting, solid-fluid equilibria, and thermodynamic properties in the high density region based on the Lennard-Jones Potential
    The Journal of chemical physics, 2017
    Co-Authors: Andreas Köster, Peter Mausbach, Jadran Vrabec
    Abstract:

    The Lennard-Jones Potential is used to study the high density fluid and face centered cubic solid state region, including solid-fluid equilibria. Numerous thermodynamic properties are considered, elucidating the behavior of matter in this poorly studied region. The present molecular simulation results are extensively compared to the latest and most accurate equation of state models for fluid and solid phases. It is shown that current models do not cover the thermodynamics of the system adequately near the solid-fluid phase transition. Furthermore, thermodynamic stability is analyzed, indicating that published solid-fluid coexistence data may not be correct at high temperatures. Particular attention is paid to the premelting zone, a range of states close to the melting line, which is characterized by strong variations of several thermodynamic properties. Because the underlying microscopic mechanisms are not yet fully understood, it is hoped that these data may contribute to the development of a theoretical framework for describing premelting effects.

  • How well does the Lennard-Jones Potential represent the thermodynamic properties of noble gases?
    Molecular Physics, 2016
    Co-Authors: Gábor Rutkai, Monika Thol, Roland Span, Jadran Vrabec
    Abstract:

    ABSTRACTThe Lennard-Jones Potential as well as its truncated and shifted (rc = 2.5σ) variant are applied to the noble gases neon, argon, krypton, and xenon. These models are comprehensively compared with the currently available experimental knowledge in terms of vapour pressure, saturated liquid density, as well as thermodynamic properties from the single phase fluid regions including density, speed of sound, and isobaric heat capacity data. The expectation that these Potentials exhibit a more modest performance for neon as compared to argon, krypton, and xenon due to increasing quantum effects does not seem to hold for the investigated properties. On the other hand, the assumption that the truncated and shifted (rc = 2.5σ) variant of the Lennard-Jones Potential may have shortcomings because the long range interactions are entirely neglected beyond the cut-off radius rc, are supported by the present findings for the properties from the single phase fluid regions. For vapour pressure and saturated liquid d...

Moustafa Sayem El-daher - One of the best experts on this subject based on the ideXlab platform.

  • Temperature dependence of the specific volume of Lennard-Jones Potential and applying in case of polymers and other materials
    Polymer Bulletin, 2020
    Co-Authors: Marwan Al-raeei, Moustafa Sayem El-daher
    Abstract:

    Based on solutions of the Ornstein–Zernike equation, we derive analytical formula for the specific volume of polymers interacting through Lennard-Jones Potential. We use mean spherical approximation assuming that the system is of low density, homogeneous, isotropic and composed of one component. The specific volumes of some polymers in addition to the minimum volumes of Lennard-Jones Potential and the specific volumes of proteinogenic amino acids: A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y and V, are calculated according to that formula. We show that the simple formula we derive is reliable and agrees well with results obtained from experimental and fitting reported in other studies. We believe that it can be used for many systems described by Lennard-Jones Potential such as biological systems, soft matter systems, large molecules such as polymers and inert gases fluids like liquid argon.

  • Analytical formula of heat capacity in soft matter materials using Lennard-Jones Potential
    Chemical Physics Letters, 2019
    Co-Authors: Marwan Al-raeei, Moustafa Sayem El-daher
    Abstract:

    Abstract We derive an analytical formula of heat capacity based on the solutions of Ornstein–Zernike equation of Lennard-Jones Potential within the Mean Spherical Approximation (MSA) assuming that the system is of low density, homogeneous, isotropic and composed of one component. We apply the derived formula to find the heat capacity at constant volume and the heat capacity at constant pressure for a number of polymers namely: Polycarbonate, Polymethylmethacrylate, Polystyrene, Polyacrylonitrile, Polyvinyl acetate, Polyvinyl propionate, Polybutylacrylate and Polyisobutylmethacrylate polymers. We also calculate the heat capacity at constant volume and the heat capacity at constant pressure for some hydrocarbons.

Richard J. Sadus - One of the best experts on this subject based on the ideXlab platform.

  • The Widom Line and the Lennard-Jones Potential.
    The journal of physical chemistry. B, 2019
    Co-Authors: James Losey, Richard J. Sadus
    Abstract:

    The phenomenological behavior of the Widom line above the vapor-liquid critical point for the Lennard-Jones (LJ) Potential is investigated using four accurate equations of state (EoS) and a comparison with molecular dynamics (MD) simulation data. This involved calculating the supercritical maximum values of the isochoric heat capacity (CV), isobaric heat capacity (Cp), isothermal compressibility (βT), and thermal expansion coefficient (αp). All LJ EoS predict the pressure (p)-temperature (T) Widom line behavior. In contrast, the T-density (ρ) Widom line behavior, observed in MD simulations, is not predicted by any LJ EoS. The calculations highlight the important role of βT in determining the range of p and T for which Widom line behavior is observed. Analysis of MD data for the supercritical maximum/minimum of CV and Cp suggests the extension of a Clausius-Clapeyron-type relationship from the triple point to the supercritical region. This provides a new description of the Widom line as the near critical part of this larger curve for which other thermodynamic functions also have maximum values.

  • Molecular simulation of orthobaric isochoric heat capacities near the critical point.
    Physical Review E, 2019
    Co-Authors: Richard J. Sadus
    Abstract:

    A molecular simulation strategy is investigated for detecting the divergence of the isochoric heat capacity (C_{V}) on the vapor and liquid coexistence branches of a fluid near the critical point. The procedure is applied to the empirical Lennard-Jones Potential and accurate state-of-the-art ab initio two-body and two-body + three-body Potentials for argon. Simulations with the Lennard-Jones Potential predict the divergence of C_{V}, and the phenomenon is also observed for both two-body and two-body + three body Potentials. The Potentials also correctly predict the crossover between vapor and liquid C_{V} values and the subcritical liquid C_{V} minimum, which marks the commencement C_{V} divergence. The effect of three-body interactions is to delay the onset of divergence to higher subcritical temperatures.

Dariusz Chocyk - One of the best experts on this subject based on the ideXlab platform.

  • Molecular dynamics study of roughness and stress evolution using a Lennard--Jones Potential
    Molecular Physics, 2007
    Co-Authors: T. Zientarski, Dariusz Chocyk
    Abstract:

    A three-dimensional molecular dynamics simulation (MD) is proposed to study the film growth, roughness and stress evolution during atoms deposition on the (100) plane of a fcc regular crystal. We use cubic system with x-y periodic boundary condition. At the bottom we have an atomic surface and at the top a reflecting wall. The model uses the Lennard-Jones Potential to describe the interatomic forces. The simulation results show that the film grows with the Volmer-Weber mode and exhibits specific curve shape of the stress evolution. The mean biaxial stress obtained during the simulation attains a local tension maximum at a coverage of two monolayers. The stress in normal direction is smaller than the biaxial stress. The main contribution to the stress in the film arises from the first monolayer. The curves describing roughness possess maximum values at the same substrate coverage. The dependence of the roughness on the temperature is examined.

  • Molecular dynamics study of roughness and stress evolution using a Lennard–Jones Potential
    Molecular Physics, 2007
    Co-Authors: Tomasz Zientarski, Dariusz Chocyk
    Abstract:

    A three-dimensional molecular dynamics (MD) simulation is proposed to study the film growth, roughness and stress evolution during atom deposition on the (100) plane of a fcc regular crystal. We use the cubic system with an x–y periodic boundary condition. At the bottom we have an atomic surface and at the top a reflecting wall. The model uses the Lennard-Jones Potential to describe the interatomic forces. The simulation results show that the film grows with the Volmer–Weber mode and exhibits specific curve shape of the stress evolution. The mean biaxial stress obtained during the simulation attains a local tension maximum at a coverage of two monolayers. The stress in the normal direction is smaller than the biaxial stress. The main contribution to the stress in the film arises from the first monolayer. The curves describing roughness possess maximum values at the same substrate coverage. The dependence of the roughness on the temperature is examined.

  • Molecular dynamics study of roughness and stress evolution using a Lennard–Jones Potential
    Molecular Physics, 2007
    Co-Authors: T. Zientarski, Dariusz Chocyk
    Abstract:

    International audienceA three-dimensional molecular dynamics simulation (MD) is proposed to study the film growth, roughness and stress evolution during atoms deposition on the (100) plane of a fcc regular crystal. We use cubic system with x-y periodic boundary condition. At the bottom we have an atomic surface and at the top a reflecting wall. The model uses the Lennard-Jones Potential to describe the interatomic forces. The simulation results show that the film grows with the Volmer-Weber mode and exhibits specific curve shape of the stress evolution. The mean biaxial stress obtained during the simulation attains a local tension maximum at a coverage of two monolayers. The stress in normal direction is smaller than the biaxial stress. The main contribution to the stress in the film arises from the first monolayer. The curves describing roughness possess maximum values at the same substrate coverage. The dependence of the roughness on the temperature is examined

Andreas A. Polycarpou - One of the best experts on this subject based on the ideXlab platform.

  • Adhesive contact based on the Lennard-Jones Potential: a correction to the value of the equilibrium distance as used in the Potential
    Journal of colloid and interface science, 2004
    Co-Authors: Andreas A. Polycarpou
    Abstract:

    Abstract A Lennard–Jones type surface law is commonly used in adhesive contact modeling; however, one of its parameters, namely the equilibrium distance z0, is not well defined. In this paper, a self-consistent method is used to derive the Lennard–Jones surface law from the interatomic Lennard–Jones Potential. The parameters of the surface law are directly related to the material lattice parameter and surface energy, and the equilibrium distance z0 values are obtained for various materials. The effect of using the z0 proposed in the present work is demonstrated via the study of adhesive contact behavior for a single sphere and a flat surface, as well as the contact between planar rough surfaces. For pull-off force prediction of the contact between a single sphere and a flat surface, the error of using the z0 suggested in previous studies could be as large as 10% at intermediate ranges of a dimensionless adhesion parameter. For the contact between planar rough surfaces, the error of using the previously proposed z0 is larger for smoother cases, and the prediction of pull-off force could be different by as much as a factor of 5.