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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.

We present the results of a first principles study on the ordered Ge[sub 0.50]C[sub 0.50] and Sn[sub 0.50]C[sub 0.50] cubic alloys. A linear combination of atomic orbitals approach in the framework of density functional theory is employed for total energy calculations in the zincblende phase. A fitting of the energy surface to the equation of state yields the lattice constant of 4.61 and 5.17 Å and the bulk modulus of 181 and 119 GPa for GeC and SnC, respectively. Analysis of band structure suggests a crossover of the nature of the band gap from indirect to direct in going from SiC to GeC to SnC. Although both alloys predicted to be unstable with respect to their elemental components at zero pressure and temperature, GeC appears to become stable at higher pressure. It appears that both the lattice constant and bulk modulus of the ordered alloys do not follow Végard's linear rule, though the calculated dielectric constant of the cubic alloys is approximately the average of the dielectric constant of their elemental components. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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.

Studies the structural, electronic, and optical properties of the ordered Ge[sub 0.50]Sn[sub 0.50] alloy in the zinc-blende phase along with its stability with respect to the elemental components. Electron density functional theory calculations; Linear combination of atomic orbitals approach; Bloch functions.