Showing papers by "Robert Evans published in 1984"

A simple density functional theory for inhomogeneous liquids

Abstract: A simple free energy functional, which incorporates both ‘local’ thermodynamics and short ranged correlations, is formulated and applied to the calculation of the density profile of fluids near hard walls. For hard sphere fluids the calculated profiles are in reasonable agreement with Monte Carlo results. For a Lennard-Jones liquid the profiles exhibit the phenomenon of wetting by gas; the oscillations in the density profiles become much less pronounced and a layer of gas develops near the wall as the bulk density approaches its value at coexistence. Such behaviour was found earlier in Monte Carlo simulations but is not accounted for by existing integral equation theories based on closures of the wall-particle Ornstein-Zernike equation.

Theory of condensation in narrow capillaries

Abstract: By means of a density functional approach, the phase equilibria of a fluid confined between two adsorbing walls, i.e., in a slitlike capillary, have been investigated. The theory provides a microscopic basis for the phenomenon of capillary condensation and, for fluids in narrow slits, predicts a line of critical points marking the end of the lines of coexistence between "liquid" and "gas" phases.

Rapid evolution of a Gulf Stream warm-core ring

Abstract: Satellite images are used to show that major alterations in the structure of Gulf Stream warm-core rings can occur during very short periods of two to five days when an interaction with the Gulf Stream is particularly intense. The role of these interactions in the evolution of a ring are discussed.

A comment on the order of the wetting transition at a solid–fluid interface

Abstract: We have repeated calculations of Teletzke et al. which describe the wetting transition at some models of a solid–gas interface. Our numerical results differ significantly from theirs in several cases. Contrary to Teletzke et al. we find that this transition is always first order for a Lennard‐Jones 9‐3 substrate potential when the van der Waals integral theory is employed.

The surface tension of non-critical interfaces near critical end points

Abstract: We have calculated the surface tension σ of the non-critical interfaces which occur near the critical end point for liquid-liquid phase separation. Our calculations are based on a non-local, two-density, mean field approximation to the free energy functional. For both liquid-gas and solid-liquid non-critical interfaces we find that σ and its temperature derivative dσ/dT are continuous at the critical end point. If, however, our results are plotted on an unexpanded temperature scale dσ/dT sometimes appears discontinuous. Our analysis suggests that experiments aimed at testing the prediction that dσ/dT is continuous will have to be performed at temperatures closer to the critical end point than those performed hitherto.

Critical Exponents for Complete Wetting

Abstract: En relation avec un travail de R. Lipowski (ibid., 1984, 52, 1429) sur les exposants critiques, relatifs a la divergence des quantites interfaciales dans les limites du mouillage total d'une interface gaz-solide par une phase liquide adsorbee

A model for the structure of liquid Li4Pb

Abstract: We present the results of calculations of the partial structure factors and radial distribution functions of liquid Li 4 Pb at different temperatures. Assuming that this alloy is partially ionic, we have modelled the interionic forces by pairwise potentials that are strongly repulsive at small separations r and electronically screened Coulombic at large r. This model was motivated by the fact that a r dependent ‘ordering potential’ which exhibits approximately screened Coulombic decay for a large r, can be extracted from the neutron diffraction data for S cc (q) in Li 4 Pb. Our calculations, which are based on the mean-spherical and the hyper-netted-chain approximations, show that the wave number dependence of the measured concentration structure factor S cc (q) can be reasonably well accounted for by our model with effective electron charges of about 0.5 and −2.0 at the Li and Pb sites, respectively, and an inverse screening length of 1·1 A −1 . These parameters are consistent with values obtained from the ordering potential extracted from experiment. In order to explain the observed temperature dependence of S cc (q) it is necessary to assume that the charge transfer between species decreases with increasing temperature.