Investigation and improvement of equations of state for Lennard-Jones fluid
TL;DR: In this article, the performance of three perturbation-theory-based equations of state (EOSs) for the Lennard-Jones (L-J) fluid were compared with two modified 33-parameter BWR EOSs.
About: This article is published in Fluid Phase Equilibria.The article was published on 1997-01-15. It has received 21 citations till now.
Citations
More filters
TL;DR: In this article, the mathematical model of calculation of thermophysical properties for nanofluids on the basis of statistical nanomechanics is presented, and the analytical results obtained by statistical mechanics are compared with the experimental data and show relatively good agreement.
120 citations
TL;DR: In this article, the sensitivity of thermodynamics to the Barker-Henderson (BH) diameter for the Lennard-Jones (LJ) potential is discussed, which covers both its approximation in calculation and improvement in rationality.
Abstract: Sensitivity of thermodynamics to the Barker–Henderson (BH) diameter for the Lennard-Jones (LJ) potential is discussed, which covers both its approximation in calculation and improvement in rationality. With regarding to the approximation, pressure and internal energy for the LJ fluid, LJ chains and LJ chain mixtures are investigated. It is found that internal energy is much more sensitive to an approximation to the diameter than pressure for pure fluids, and both pressure and internal energy are very sensitive to the diameter for mixtures. It is also found that the approximating expression given by Cotterman et al. (1986) covers the widest range of temperatures. The rationality of the BH diameter itself at very high temperatures and densities is also analyzed. Through a functional expansion of Helmholtz free energy, we conclude that a density-dependent BH diameter is fundamentally more appropriate. The proposed diameter yields almost the same results as the original BH diameter at normal conditions and remedies its deficiencies at extreme ones. The density-dependent diameter provides a convenient way to study the LJ systems undergoing gas-solid phase transition or freezing.
42 citations
TL;DR: In this article, the statistical associating fluid theory (SAFT) equation of state is employed for the correlation and prediction of vapor−liquid equilibrium (VLE) of binary mixtures of alcohols with water, carbon and carbon dioxide.
Abstract: The statistical associating fluid theory (SAFT) equation of state is employed for the correlation and prediction of vapor−liquid equilibrium (VLE) of binary mixtures of alcohols with water, carbon ...
34 citations
TL;DR: A statistical associating fluid theory (SAFT) equation of state, incorporated with mean spherical approximation (MSA), has been established to calculate the activity coefficients of surfactants in aqueous solutions as discussed by the authors.
21 citations
TL;DR: In this paper, the SAFT-VR EOS for LJ fluids and its simplified form by mean-field approximation are compared with the Cotterman EOS, and the accuracy of predictions for liquid-liquid equilibria (LLE) of binary LJ mixtures is also examined.
16 citations
References
More filters
TL;DR: In this article, the perturbation theory for the 6:12 potential is applied to more realistic potentials with soft repulsion, and the configuration integral is expanded in a double-power series in the inverse-steepness and depth parameters.
Abstract: The perturbation theory previously shown to give good results for the equation of state of a square‐well fluid at liquid densities and temperatures is applied to more realistic potentials with soft repulsion, in particular the 6:12 potential. For an arbitrary potential function a modified potential is defined involving three parameters, namely a hard‐sphere diameter, an inverse‐steepness parameter for the repulsive region, and a depth parameter for the attractive region. When the latter parameters are zero, the modified potential becomes the hard‐sphere potential; when they are one, it becomes the original potential. The configuration integral is expanded in a double‐power series in the inverse‐steepness and depth parameters, the hard‐sphere diameter being chosen so that the first‐order term in the inverse‐steepness parameter is zero. The first‐order term in the depth parameter is evaluated essentially exactly and the second‐order term approximately: other second‐order terms and all higher‐order terms are neglected. The resulting equation of state is in good agreement with molecular dynamics, Monte Carlo results, and experimental data for argon at all temperatures and densities relevant for fluids.
1,469 citations
TL;DR: In this paper, a modified Benedict-Webb-Rubin (MBWR) equation of state for the Lennard-Jones (LJ) fluid is presented and compared with the simulation data of this work, and previously published Gibbs ensemble data.
Abstract: We review the existing simulation data and equations of state for the Lennard-Jones (LJ) fluid, and present new simulation results for both the cut and shifted and the full LJ potential. New parameters for the modified Benedict-Webb-Rubin (MBWR) equation of state used by Nicolas, Gubbins, Streett and Tildesley are presented. In contrast to previous equations, the new equation is accurate for calculations of vapour-liquid equilibria. The equation also accurately correlates pressures and internal energies from the triple point to about 4·5 times the critical temperature over the entire fluid range. An equation of state for the cut and shifted LJ fluid is presented and compared with the simulation data of this work, and previously published Gibbs ensemble data. The MBWR equation of state can be extended to mixtures via the van der Waals one-fluid theory mixing rules. Calculations for binary fluid mixtures are found to be accurate when compared with Gibbs ensemble simulations.
1,247 citations
TL;DR: The perturbation theory of liquids developed recently by Weeks, Chandler, and Andersen (WCA) is examined in detail: each assumption introduced by these authors is tested by comparison with "exact" computer results as discussed by the authors.
Abstract: The perturbation theory of liquids developed recently by Weeks, Chandler, and Andersen (WCA) is examined in detail: Each assumption introduced by these authors is tested by comparison with "exact" computer results. It is shown that the basic assumptions of WCA are justified. An improved expression for the radial distribution function of the hard-sphere gas enables us to correct for some further inconsistent assumptions of the WCA theory. We then succeed in giving simple analytical expressions for the thermodynamic functions of the Lennard-Jones fluid shown to be quite good at high density. We show that the remainder of the perturbation series, which converges slowly at lower density, can be evaluated with the help of the Percus-Yevick equation. We therefore possess a unified theory of liquids which is especially simple at high density. Finally we reexpress the original WCA theory in an analytical form.
1,111 citations
TL;DR: In this article, a modified Benedict-Webb-Rubin equation has been used to derive an equation of state for the Lennard-Jones fluid that is valid over a wide range of temperatures and densities.
Abstract: Molecular dynamics calculations of the pressure and configurational energy of a Lennard-Jones fluid are reported for 108 state conditions in the density range 0·35 ≦ ρ* ≦ 1·20 and temperature range 0·5 ≦ T* ≦ 6 (where ρ* = ρσ3, T* = kT/e). Particular attention is paid to the dense fluid region (ρ* ≧ 0·9), including state conditions in the subcooled liquid region. These new simulation results for P and U are combined with those of previous workers, together with low density values calculated from the virial series and values of the second virial coefficients themselves, to derive an equation of state for the Lennard-Jones fluid that is valid over a wide range of temperatures and densities. The equation of state used is a modified Benedict-Webb-Rubin equation having 33 constants. It fits the data well over the density range 0 ≦ ρ* ≦ 1·2 and for T* values ranging from 0·5 to 6·0 (the exact temperature range depending to some extent on the density considered). We also calculate for the same range of state con...
720 citations
TL;DR: In this paper, a perturbed virial expansion with a theoretically defined temperature-dependent reference hard sphere term is proposed to guarantee the thermodynamic consistency of the pressure and internal energy of the Lennard-Jones fluid.
276 citations