Adsorption of chlorine on Ru(0001)-A combined density functional theory and quantitative low energy electron diffraction study

► p(√3 × √3)R30°-Cl phase, ΘCl = 1/3 ML in fcc sites identified to be the most stable adsorbate structure on Ru(0001). ► Structural parameters of this phase determined by quantitative LEED (rP = 0.19) and DFT calculations. ► p(√3 × √3)R30°-Cl island formation indicated by LEED at low Cl coverage. ► Complex compressed overlayer structures form at Cl coverage > 1/3 ML. ► Structure can be used for Auger electron intensity calibration.