One-dimensional commensurate-incommensurate transition: Bromide on the Au(100) electrode

In an electrochemical environment, bromide adsorbed on the Au(100) surface forms a commensurate c(root 2X2 root 2)R45 degrees monolayer over a range of applied potentials. At a critical potential the bromide monolayer undergoes a transition to a uniaxial-incommensurate c(root 2Xp)R45 degrees monolayer, where p continuously decreases from 2 root 2 with increasing potential. In the incommensurate phase, the data support an atomic model with uniform compression rather than sharp, well-ordered domain walls. The quadratic scaling of the peak widths with the incommensurate component of the wave vector suggests that the incommensurate phase exhibits ''cumulative disorder.''