Angular motion of molecular adsorbates influenced by surface coverage

Using classical dynamics, we show that the angular motion of an adsorbate is strongly modified by the surface coverage. Increasing this coverage from submonolayer to monolayer changes the mean angles and rigidifies the structures about the azimuthal angle. Consequently, lateral interaction, including an angular term, should be taken into account in dynamical studies of adsorbates. These conclusions were reached in the particular case of CO/Ar(100) but we believe that they are valid for other systems.