Pair correlation function of short-ranged square-well fluids

Abstract

We have performed extensive Monte Carlo simulations in the canonical (NVT) ensemble of the pair correlation function for square-well fluids with well widths lambda-1 ranging from 0.1 to 1.0, in units of the diameter sigma of the particles. For each one of these widths, several densities rho and temperatures T in the ranges 0.1< or =rhosigma(3)< or =0.8 and T(c)(lambda) less or approximately T less or approximately 3T(c)(lambda), where T(c)(lambda) is the critical temperature, have been considered. The simulation data are used to examine the performance of two analytical theories in predicting the structure of these fluids: the perturbation theory proposed by Tang and Lu [Y. Tang and B. C.-Y. Lu, J. Chem. Phys. 100, 3079 (1994); 100, 6665 (1994)] and the nonperturbative model proposed by two of us [S. B. Yuste and A. Santos, J. Chem. Phys. 101 2355 (1994)]. It is observed that both theories complement each other, as the latter theory works well for short ranges and/or moderate densities, while the former theory works for long ranges and high densities.

Alternative Approaches to the Equilibrium Properties of Hard-Sphere Liquids

“…As an illustration, Fig. 13 compares the RDF provided by the RFA with Monte Carlo data [111] for three representative cases.…”

“…It can be proven that the RFA proposal (198) reduces to the exact solutions of the PY equation [29,94] in the HS limit, i.e., ǫ → 0 or R → 1, and in the SHS limit, i.e., ǫ → ∞ and R → 1 with (R − 1)e 1/T * = finite [107,108]. Comparison with computer simulations [107,108,110,111] shows that the RFA for SW fluids is rather accurate at any fluid density if the potential well is sufficiently narrow (say R ≤ 1.2), as well as for any width if the density is small enough (say ρσ 3 ≤ 0.4). However, as the width and/or the density increase, the RFA predictions worsen, especially at low temperatures.…”

Theoretical approaches to the structural properties of the square-shoulder fluid

“…The presentation follows very closely the one given for the square-well (SW) fluid in Ref. [38] with the simple replacement of T * by −T * .…”

Structural and thermodynamic properties of argon liquid as a square-well fluid based on a modification of the ORPA theory

“…Figure 2 shows the comparison of the calculated g(σ + ) for argon fluid with λ = 1.7 along the isotherm T = 186.6 K as a function of density, with the simulation data. [42] The variation of the peak of g(r) to the density is due to the clustering of particles near contact distance in which it remains nearly constant at low density region and increases corresponding to increasing density. It is interesting that our calculations carried out at a wide range of densities can present qualitatively the behaviour of g(σ + ).…”