Effects of lateral diffusion on morphology and dynamics of a microscopic lattice-gas model of pulsed electrodeposition

TL;DR

This study uses kinetic Monte Carlo simulations to examine how lateral diffusion affects the phase transformation dynamics in a lattice-gas model of electrochemical metal deposition, revealing diffusion-dependent acceleration and a crossover to instantaneous nucleation at high rates.

Contribution

It provides new insights into the role of lateral diffusion in phase transformation kinetics and introduces a refined approach to estimate cluster free energies beyond classical droplet theory.

Findings

Diffusion accelerates phase transformation up to moderate rates.

High diffusion rates cause a shift to instantaneous nucleation.

Large clusters tend to grow during initial desorption stages.

Abstract

The influence of nearest-neighbor diffusion on the decay of a metastable low-coverage phase (monolayer adsorption) in a square lattice-gas model of electrochemical metal deposition is investigated by kinetic Monte Carlo simulations. The phase-transformation dynamics are compared to the well-established Kolmogorov-Johnson-Mehl-Avrami theory. The phase transformation is accelerated by diffusion, but remains in accord with the theory for continuous nucleation up to moderate diffusion rates. At very high diffusion rates the phase-transformation kinetic shows a crossover to instantaneous nucleation. Then, the probability of medium-sized clusters is reduced in favor of large clusters. Upon reversal of the supersaturation, the adsorbate desorbs, but large clusters still tend to grow during the initial stages of desorption. Calculation of the free energy of subcritical clusters by enumeration of lattice animals yields a quasi-equilibrium distribution which is in reasonable agreement with the simulation results. This is an improvement relative to classical droplet theory, which fails to describe the distributions, since the macroscopic surface tension is a bad approximation for small clusters.