Voltage-Dependent Cluster Expansions for Modeling Catalytic Electrochemical Interfaces in Solution Environments*

The cluster expansion method provides the framework to represent functions of lattice configurations. We use this method to model energetics of solid-solution interfaces in electrochemical systems. Semi-local density functional theory calculations with implicit solvation are used to obtain effective cluster interactions that include local relaxations and the effects of the solvent. These calculations, in conjunction with electrochemical double layer models, provide the framework for voltage-dependent cluster expansions in a model electrochemical environment. We use these voltage-dependent cluster expansion to model faradaic charging at electrode-electrolyte interfaces, equilibrium configurations of surface alloys, and surface promotion in near-surface alloys. Preliminary voltage-dependent cluster expansion models of skin alloys suggest that amount of catalytically active sites highly sensitive to the applied potential.