Combined density functional theory (DFT) and Monte Carlo (MC) approach is applied to study the potential energy landscape of four iodine atoms adsorbed on the Pt(111) surface in a ($3\times 3$) unit cell. Three critical points were identified: ($3\times 3$)-sym and ($3\times 3$)-asym, corresponding to structures well known from experimental studies, while the third one ($3\times 3$)-zigzag is a new structure not reported before. An interaction model fitted to DFT calculations allows us to explain the difference between arrangements of iodine monolayer in vacuum, air, and solution environments as a result of different repulsion regimes.

• Received 21 March 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.036102