A modified diffusion-limited aggregation simulation of electrodeposition

A modified diffusion limited aggregation simulation of electrodeposition was investigated in two and three dimensions. The simulation parameters included a global sticking coefficient (elastic barrier) which mimics the ratio of the current density to the magnitude of the overpotential and a variable uniform drift distance (biased random walk) which mimics the magnitude of the overpotential. The aggregates which were grown in the simulation exhibited both open dendritc and compact mossy forms. Some well known geometric quantities which characterize aggregate morphologies were calculated along with the probability density of open sites and its moments. The number of open or unoccupied nearest neighbor sites surrounding an occupied site in the aggregate provides a statistical description of aggregate morphology. The aggregate surface radius of curvature was determined by the simulation parameters by an equation of state inherent in the simulations in an asymptotic growth regime. A macroscopic equation of state for electrodeposition, the modified Barton-Bockris equation, which includes corrections for both electrocapillarity and the curvature dependence of the surface free energy, was found to adequately describe both the small radius dendrite and the large radius mossy phases found in the simulation results. A statistical mechanical description of aggregate surface curvature is included.