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 $c(\sqrt{2}\times 2\sqrt{2})R45\mathrm{}°$ monolayer over a range of applied potentials. At a critical potential the bromide monolayer undergoes a transition to a uniaxial-incommensurate $c(\sqrt{2}\times p)R45\mathrm{}°$ monolayer, where $p$ continuously decreases from $2\sqrt{2}$ 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."