Phase diagram of O/Ru(0 0 0 1) from first principles

The lattice gas model with hcp and fcc sites is used to study the O/Ru(0 0 0 1) adsorbate system. With interactions obtained from density functional theory its phase diagram is calculated using Monte Carlo simulations. Good qualitative agreement is obtained between experiment and theory; better quantitative agreement occurs if the interactions are scaled by a factor of 3/4. A (3×3)∗R30° structure at a coverage of 2/3 ML is predicted.