MONTE-CARLO SIMULATION OF XE ADSORBED ON AL(110)

A Monte Carlo simulation of the Xe/Al(110) system has been performed i n order to study the two-dimensional (2D) phase transition previously detected by spectroscopic and diffraction experiments at temperature o f 45 K and low submonolayer coverage, theta (Xe), of about 0.1 monolay er. The simulation results suggest that the microscopic origin of this structural transition is a change in the adsorption geometry of the a datoms from 2D commensurate islands to incommensurate ones as a functi on of Xe coverage. The shortening of the Xe-Xe distance in the incomme nsurate structure agrees with LEED experiments on this system. These r esults are in contradiction with the original suggestion, based on TDS and UPS low coverage data, of a 2D-ps 2D-solid transition due to the formation of Xe islands at T = 45 K and theta (Xe) = 0.1. We show that a lattice-ps model predicts formation of Xe islands at Xe coverages m uch lower than 0.1 monolayer at the studied temperature.