RIGOROUS ANALYSIS OF LOW-TEMPERATURE PHASES IN A MODEL FOR UNDERPOTENTIAL DEPOSITION OF COPPER ON THE (111) SURFACE OF GOLD IN THE PRESENCEOF BISULFATE

A model for two-component coadsorption is introduced and used to study the structure of the phases which occur at low temperature during the underpotential deposition of copper on the (111) surface of gold in t he presence of bisulfate ions. The structure,of the voltage dependent ground state configurations is rigorously obtained, and the Pirogov-Si nai theory is used to prove the existence of low-temperature phases in the model which are similar in structure to the ground state configur ations. The sequence and structure of the low-temperature phases which occur in the model as the voltage is changed are essentially the same as those obtained experimentally at ambient temperatures during the u nderpotential deposition process.