A new semi-empirical model for the oxidation of polycyclic aromatic hydrocarbon (PAHs) molecules physisorbed on soot. II. Application to the reaction PAHÂ +Â OH for a series of large PAH molecules

In the present paper, we apply our new semi-empirical method to characterize the oxidation by OH of a series of large polycyclic aromatic hydrocarbons (PAHs) adsorbed on a soot surface modeled by a large graphene-like cluster. This method is based on an electrostatic and induction contribution calculated at the SCF AM1 level to which a sum of two-body terms of the C(6)/R6 form has been added to represent the dispersion interactions. This so-called AM1-D method is used to compare the oxidation reaction kinetics at carbonaceous surfaces and in the gas phase. First, the satisfying comparison between the calculated adsorbed energies of a series of eight PAH molecules and the recent determinations of experimental values demonstrates the validity of this method. Moreover, our calculations evidence a small inhibition of the oxidation process by the carbonaceous surface, at least for a majority of the PAH molecules considered in our study. This result is in qualitative agreement with recent experimental conclusions.