The phase diagram of halogens on Pt(110): structure of the(4 × 1)-Br/Pt(110) phase

Abstract

When adsorbed on the strongly anisotropic Pt(110) surface Br forms a sequence of(n × 1) structures. In the present study we investigate the(4 × 1) structure by scanning tunneling microscopy, quantitative low-energy electrondiffraction and density-functional calculations. We show that the optimalstructural model contains essentially the same adsorption sites as the(3 × 1) structure, but with a different preference. The positions of the substrate atom areconsistent with a frozen surface phonon of fourfold periodicity, suggesting that the phasediagram can be understood on the basis of a tunable charge density wave (Swamy et al 2001Phys. Rev. B 86 1299). The structure could also be explained by assuming short-rangeinteractions only, but evidence is presented that adsorbate–adsorbate interactionsmediated by quasi-one-dimensional surface resonances play a major role in bothcases.