  Numerical studies of lattice-gas models are well suited to describe
multi-adsorbate systems. One example is the underpotential deposition of Cu on
Au(111) in the presence of sulfuric acid. Preliminary results from dynamic
Monte Carlo simulations of the evolution of the adsorbed layer during
potential-step experiments across phase transitions are presented for this
particular system. The simulated current profiles reproduce a strong asymmetry
seen in recent experiments. Examination of the microscopic structures that
occur during the simulated evolution processes raises questions that need to be
investigated by further experimental and theoretical study.
