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The ozonization mechanism for polycyclic aromatic hydrocarbons and soot is investigated by quantum mechanical calculations carried out on molecular and periodic systems. The results suggest that both molecular and periodic simulations of the oxidation processes of these substrates involve only their internal positions, that is, they exclude the carbon atoms located along the perimeter of the platelet.

The spin density distributions and the oxidative functionalization that odd primary aromatic hydrocarbons (PAH) undergo as a result of ozone electrophilic attack are examined. The spin density patterns were found to be dependent on the size and shape of PAH.

The viability of some nitration pathways is investigated for benzene (B), naphthalene (N) and part pyrene (P). Findings rule out the possibility of direct nitration at room temperature and instead, NO3 and, even more easily, HO can form (pi)-demoralized nitroxy- or hydroxycyclohexadienyl radicals.

The properties of the interaction of hydrogens and nitrogens with the model systems are examined. An appropriate description of the atmospheric or combustion gas - solid interactions by which functionalization reactions can occur is provided.

A periodic slab model which varied the number of layers from two to four, was used to investigate the p(1x1) adsorption of atomic oxygen on the fcc and hcp three-fold hollow site of a Pt(111) surface. The CRYSTAL95 ab initio program was used along with the density functional method with local spin density approximation. The three-layer slab model was a good compromise between accuracy and the computational time. A delocalized interaction of the oxygen adatoms to the surface was indicated by the three-dimensional difference electron density plots.