MOLECULAR-DYNAMICS STUDY OF THE COVERAGE DEPENDENCE OF XE DESORPTION FROM PT(111)

Molecular dynamics simulations with periodic boundary conditions are used to calculate temperature-programmed desorption spectra of Xe/Pt(111). The activation barrier is overcome using the compensating Hamiltonian method. Monte Carlo simulations am used to correct for the finite size of the simulated system. A comparison between calculated and experimental temperature-programmed desorption spectra shows that there is a strong reduction in the Xe-Xe attraction due to substrate-mediated effects. Still, strong island formation occurs. In spite of the fact that Xe atoms in islands desorb less easily than isolated Xe atoms, the desorption from islands dominates at low temperature, and the desorption of isolated Xe atoms at high temperature. This is caused by the variation m the number of isolated Xe atoms and Xe atoms in islands as a function of temperature and coverage.