arXiv subjects

Gregory Brown

Publications and source records attributed to Gregory Brown.

20 records · Page 2Linked to original sources

arXiv1997

Equilibrium and nonequilibrium applications of lattice-gas models in electrochemistry

We discuss applications of statistical-mechanical lattice-gas models to study static and dynamic aspects of electrochemical adsorption. The strategy developed to describe specific systems includes microscopic model formulation, calculation of zero-temperature phase diagrams, numerical simulation of thermodynamic and structural quantities at nonzero temperatures, and estimation of effective, lateral interactions. We briefly review earlier work, including studies by Monte Carlo simulation of the adsorption of urea on Pt(100). As an illustrative example, we discuss in some detail recent applications to the underpotential deposition of Cu with sulfate on Au(111). Experimental and numerical results are included for equilibrium coverages and voltammetric currents at slow potential sweep rates, and new results from dynamic Monte Carlo simulations are presented. In particular, we present simulated results for current transients far from equilibrium, following sudden changes in the electrode potential.

cond-mat↗

arXiv1996

Numerical simulations of scattering speckle from phase ordering systems

The scattering of coherent X-rays from dynamically evolving systems is currently becoming experimentally feasible. The scattered beam produces a pattern of bright and dark speckles, which fluctuate almost independently in time and can be used to study the dynamics of the system. Here we report large-scale computer simulations of the speckle dynamics for a phase ordering system, using a two-dimensional model quenched through an order--disorder transition into the two-phase regime. The intensity at each wave vector ${\bf k}$ is found to be an exponentially distributed random variable. The scaling hypothesis is extended to the two-time correlation function of the scattering intensity at a given wave vector, $Corr({\bf k};t_1,t_2)$. The characteristic decay time difference for the correlation function, $|t_1 - t_2|_c$, is found to scale as $k|t_1 + t_2|^{1/2}$.

cond-mat↗