BROMIDE ADSORPTION ON AG(001): A POTENTIAL INDUCED TWO-DIMENSIONAL ISING ORDER-DISORDER TRANSITION

The adsorption of bromide on an Ag(001) electrode has been investigated using {ital in situ} x-ray scattering methods. With increasing potential, the bromide undergoes a second order phase transition from a lattice gas to an ordered c(2{times}2) structure. The order parameter is consistent with the 2D Ising model prediction {beta}=1/8 . A comparison of x-ray and electrochemical measurements indicates significant lateral disorder at low coverages which decreases with increasing coverage. {copyright} {ital 1997} {ital The American Physical Society}