Orientation of small rafts of xenon atoms physisorbed on Pt(111): A molecular-dynamics study

A recent experiment using high-resolution He diffraction revealed the existence of incommensurate xenon overlayers of Pt(111). The overlayers were rotated by 30° with respect to the platinum substrate. We present here the results of a molecular-dynamics study of small rafts of xenon atoms on a Pt(111) surface. They reveal a mechanism for the 30° orientation of the incommensurate xenon. The experiments also showed the existence of a $\sqrt{3}\times \sqrt{3}R30°$ commensurate phase of xenon. In our studies of small rafts at various temperatures, and with a variety of substrate-adatom potentials, we see no existence of this phase.