Leo Lue

Renormalization-group corrections to an approximate free-energy model for simple fluids near to and far from the critical region

We combine liquid-state theory with a renormalization-group method to develop an equation of state for simple fluids that is valid near and far from the critical point. The resulting equation of state has nonclassical critical exponents close to those experimentally observed. Far away from the critical point, the equation of state reduces to that obtained by liquid-state theory. This formalism is applied successfully to square-well fluids, and to three real fluids: methane, carbon dioxide, and n-butane.

The electric double layer at high surface potentials : the influence of excess ion polarizability

By including the excess ion polarizability into the Poisson-Boltzmann theory, we show that the decrease in differential capacitance with voltage, observed for metal electrodes above a threshold potential, can be understood in terms of thickening of the double layer due to ion-induced polarizability holes in water. We identify a new length which controls the role of excess ion polarizability in the double layer, and show that when this is comparable to the size of the effective Debye layer, ion polarizability can significantly influence the properties of the double layer.

DynamO : a free O(N) general event-driven molecular dynamics simulator

Molecular dynamics algorithms for systems of particles interacting through discrete or “hard” potentials are fundamentally different to the methods for continuous or “soft” potential systems. Although many software packages have been developed for continuous potential systems, software for discrete potential systems based on event‐driven algorithms are relatively scarce and specialized. We present DynamO, a general event‐driven simulation package, which displays the optimal

Application of integral equation theories to predict the structure, thermodynamics, and phase behavior of water

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Thermodynamic pressures for hard spheres and closed-virial equation-of-state.

(N) asymptotic scaling of the computational cost with the number of particles N, rather than the

Electrostatic interactions of charged bodies from the weak- to the strong-coupling regime

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Depletion effects and gelation in a binary hard-sphere fluid

(N log N) scaling found in most standard algorithms. DynamO provides reference implementations of the best available event‐driven algorithms. These techniques allow the rapid simulation of both complex and large (>106 particles) systems for long times. The performance of the program is benchmarked for elastic hard sphere systems, homogeneous cooling and sheared inelastic hard spheres, and equilibrium Lennard–Jones fluids. This software and its documentation are distributed under the GNU General Public license and can be freely downloaded from http://marcusbannerman.co.uk/dynamo.

Electrolytes at spherical dielectric interfaces

We analyze the predictive capabilities of the site–site Ornstein–Zernike equation and the Chandler–Silbey–Ladanyi equations for various potential models of water. Specifically, we solve (i) the site–site Ornstein–Zernike equation with the hypernetted‐chain closure, and (ii) the Chandler–Silbey–Ladanyi equations with the hypernetted‐chain closure as well as with the zeroth‐order bridge functions, and compare their predictions of the structure, thermodynamics, and phase behavior of water with those obtained from computer simulations and experimental measurements. The predictions of the various site–site pair correlation functions of water for both integral equations are comparable. However, the Chandler–Silbey–Ladanyi equations seem to better predict the structure of the fluid beyond the first coordination shell. In addition, the Chandler–Silbey–Ladanyi equations provide better estimates of the thermodynamic properties of water as compared to those of the site–site Ornstein–Zernike equation, when the result...

A field theory for ions near charged surfaces valid from weak to strong couplings

Hard-sphere molecular dynamics (MD) simulation results, with six-figure accuracy in the thermodynamic equilibrium pressure, are reported and used to test a closed-virial equation-of-state. This latest equation, with no adjustable parameters except known virial coefficients, is comparable in accuracy both to Padé approximants, and to numerical parameterizations of MD data. There is no evidence of nonconvergence at stable fluid densities. The virial pressure begins to deviate significantly from the thermodynamic fluid pressure at or near the freezing density, suggesting that the passage from stable fluid to metastable fluid is associated with a higher-order phase transition; an observation consistent with some previous experimental results. Revised parameters for the crystal equation-of-state [R. J. Speedy, J. Phys.: Condens. Matter 10, 4387 (1998)] are also reported.

Application of integral equation theories to predict the structure of diatomic fluids

A simple field theory approach is developed to model the properties of charged, dielectric bodies and their associated counterions. This predictive theory is able to accurately describe the properties of systems (as compared to computer simulation data) from the weak-coupling limit, where the Poisson-Boltzmann theory works well, through to the strong-coupling limit. In particular, it is able to quantitatively describe the attraction between like-charged plates. In addition, the theory remains accurate even in the presence of dielectric bodies, properly accounting for the influence of image charge interactions. The theory is compared to the strong-coupling expansion, which is found to be applicable only in certain limited situations when dielectric variations are present.