Potential energy landscape of monolayer-surface systems governed by repulsive lateral interactions: the case of $(3 \times 3)$-I-Pt(111)

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 $(3 \times 3)$ 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.