Monte Carlo simulations of controlled rate thermal analysis spectraThe influence of surface energetic heterogeneity and lateral interactions between adsorbed molecules

Abstract

Monte Carlo simulations of controlled rate thermal analysis (CRTA) spectra are presented. Calculations are performed for a few kinds of energetically heterogeneous surface, characterized by symmetrical and unsymmetrical desorption energy distributions. It is shown that the shape of the CRTA spectra corresponds with the shape of integral form of desorption energy distribution on the surface. A simple way of estimation of the upper limit of desorption energy is proposed. The influence of lateral interactions on the shape of the CRTA spectra is also discussed. It is stated that strong attractive interactions cause the desorption temperature to be constant. As a result of repulsive interactions two steps on the desorption temperature curve are observed. For the case of repulsive interactions between the nearest-neighbors and next-nearest-neighbors the CRTA spectra do not reveal the existence of multiple steps, contrary to the classical thermodesorption spectra (TPD) where, in such a case, multiple peaks are observed.