Descrição de processos de dessorção termica por Monte Carlo dinamico

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

Dynamic Monte Carlo description of thermal desorption processes The thermal desorption of simple diatomic molecules from solid {metallic) surfaces is described as a heterogeneous Poisson Process in a lattice-gas model with two basic {local) processes: pair desorption and surface diffusion, and treated within a Dynamic ( time-dependent ) Monte Carlo procedure. From the stochastic rules it can be shown that the desorption kinetics depends directly on the local order of the adsorbates. Therefore, with an appropriate description of the local order, in the limit of fast diffusion with respect to desorption, the Monte Carlo simulations can be substituted by a differential equation formalism. In the absence of energetic interactions between the adsorbates, the limit or fast diffusion means that the adsorbates are randomly disordered and an equivalence can be found to the Polanyi- Wigner second-order differential equation for desorption. On the other hand, when including nearest and next-nearest neighbour interactions between the adsorbates, the local order can be wel1 approximated by the C2 approximation of Kikuchi s Cluster-Variation Method, and from which a differential equation procedure with self-consistently found structure forms can be derived, reproducing well the Temperature-Programmed Desorption spectra obtained by the simulation

ASSUNTO(S)

cinetica quimica fisica estatistica dessorção termica

ACESSO AO ARTIGO

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