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The analysis presents a theoretical study on the assembly and stabilization of the magic cluster, [Al.sub.4][N.sup.-] into molecular systems in sandwich-like forms. The results show that this cluster can also be used as a new superatom due to its high structural and electronic integrity.

A systematic density functional theory (DFT) calculations is performed on the stabilities and electronic properties of two different structures [Csub.58][X.sub.18] and [C.sub.58][X.sub.1], where X = H, F, and Cl. It is seen that the large energy gaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbital and the aromatic character possess high stabilities.

A series of multiply N-confused porphyrins and their Zn and Cu complexes are investigated by using density functional theory (DFT) and ZINDO/SOS methods. The findings demonstrate that the multiply N-confused results have shown that the one-photon absorption (OPA) spectra of multiply N-confused porphyrins, along with their metal complexes and derivatives are promising molecules, which can be assembled series of materials with large two-photon absorption (TPA) cross sections.

A series of ferrocenyl derivatives with TCF-type acceptors are designed, and their electronic structures and one- and two-photon absorption properties are investigated. Results reveal that ferrocenyl derivatives with TCF-type acceptors are promising candidates for two-photon absorptions (TPA) materials.

The characteristics of antiaromatic ring [pi] multi-hydrogen bonds {[H.sub.2]O}[.sub.n] - [C.sub.4][H.sub.4] (n = 1, 2) complexes are studied. One [H.sub.2]O forms a [pi] H-bond with [C.sub.4][H.sub.4] in two ways, one strong pi H-bond part is always accompanied by another H-bond part which is either a weak [pi] H-bond or [pi]-type H-bond.

The stable structures, energies, and electronic properties of neutral, cationic, and anionic clusters of Al(sub n) (n=2-10) are studied and show that the optimized structure of the clusters are more stable than corresponding ones previously reported and the stability has an odd/even alternation phenomenon. Studies on the structures of the Al(sub n)O (n=2-10) clusters show that oxygen is absorbed at the surface or inserted between Al atoms.

The complex singlet potential energy surface for the reaction of CH2OH with NO2 is explored theoretically and the initial association between CH2OH and NO2 is found to be the carbon-to-nitrogen approach forming an adduct with no barrier, followed by C-N bond rupture. A mechanistic comparison is made with the reactions CH3+NO2and CH3O+NO2, to understand the mechanism of the reaction and NO2 combustion chemistry.

The radical-radical reaction between the ketenyl radical (HCCO) and nitrogen dioxide (NO2) played a very important role in atmospheric and combustion chemistry. The result can lead to a deep understanding of the mechanism of the title reaction and can be helpful for understanding NO(sub x) combustion chemistry.

A detailed theoretical study is carried out for the unknown HCO/HOC + C(sub 2)H(sub 2) reactions at the CCSD(T)/6-311G(2d,p)//B3LYP/6-311G(d,p)+ZPVE, Gaussian-3//B3LYP/6-31G(d), and Gaussian-3//MP2(full)/6-31G(d) levels. For the HCO/HOC + C(sub 2)H(sub 2) reaction, both the most feasible C-addition channel and the slightly less competitive H-donation channel lead to P(sub 1) C(sub 2)H(sub 3) +CO.

The computational study of the complex singlet potential energy surface for the reactions of CN with NO(sub 2) including 9 minimum isomers and 10 transition states is illustrated. The study indicates that the title reaction proceeds mostly through singlet pathways and also gives an understanding on the mechanism of the title reaction and is helpful for understanding NO(sub 2)-combustion chemistry.

The multichannel reactions, HOCl + F -> products and HOBr + F -> products are investigated using the dual-level direct dynamics method. Results reveal that for the F + HOCl reaction, the reaction occurs exclusively through the hydrogen abstraction, while both hydrogen and bromine abstractions are involved in the F + HOBr reaction.

A detailed computational study is conducted on the radical-molecule reaction between the vinyl radical (C2H3) and formaldehyde (h2CO). At the Gaussian-3//B2LYP/6-31G(d) and CBS-QB3 levels, the direct H-abstraction forming C2H4+HCO has barriers of 3.9 and 4.7 kcal/mol, respectively.

The structures, energetic, spectroscopies, and isomerization of various doublet Si2CP species are explored theoretically. Implications in interstellar space and P-doped SiC vaporization processes are discussed.

A brief description on a preliminary theoretical study on the SiCN(super +)/SiNC(super +) + H2O reactions is presented. The results provide useful mechanistic information for the analogous ion-molecule reactions of the monovalent silicon-bearing ions.

A detailed potential-energy surface of C4P is established. This involves 12 minimum isomers and 27 interconversion transition states at the Becke exchange functional and nonlocal LYP correlation functional (B3LYP), quadratic configuration interaction method with single and double substitutions (QCISD), and couple cluster method with single, double and noniterative triple substitutions (CCSD(T)) (single-point) levels.

The proton transfer in NH3--HCl by only one molecule of catalyst was studied by using the MP2 method with the large 6-311++G(2d,2p) basis set. The results showed that the proton transfer occurred from HCl to NH3 when catalyst molecule A not only as a proton donor strongly donated the proton to the Cl atom, but as an acceptor strongly accepted the proton from the NH3 molecule in the cyclic H-bond structure.

The study obtained a complete description of the first hyperpolarizabilities of (HCN)n...Li and Li...(HCN)n (n=1,2,3). It indicates that these new alkali metal-molecular clusters have large nonlinear optical responses.

An investigation on the intermolecular interaction effects on the static electric properties by ab initio calculations for four dimers between two pi-systems is presented. It concluded that electron correlation effects are quite important for the calculation of the static electric properties, particularly the first and second hyperpolarizabilities.

A theoretical investigation is conducted on the dynamical properties for the two hydrogen-abstraction reactions of 1,1,1-trichlorethane (CH3CCl3) and 1,1,1-trifluoroethane (CH3CF3) with chlorine atoms over the temperature range 200-1200 K. The theoretical results indicate that for title reactions the vibrational effect is small over the whole considered temperature range and the small-curvative tunneling effect is important in the lower temperature range.

The investigation of the potential energy surface of C2H2FO at CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) level. The results show that isomers of 1, 3, 4, 5, 5', 8, 9, and 9' are stable, and the energy barriers are more than 30 kcal/mol.

The hydrogen abstraction reaction OH +HBr right arrow H2O with a small barrier is studied. Results indicate that a variational effect should be considered for the rate constants at high temperatures.

An exploration of the potential energy surfaces of the interstellar molecule SiC2N at the B3LYP/6-311G(d), QCISD/6-311G(D) and CCSD(T)/6-311G(2d) (single point) levels is presented. The calculated bond lengths, harmonic vibrational frequencies, dipole moments, rotational constants and the first excitation energies derived here can assist in future laboratory and interstellar identification of the three SiC2N isomers SiCCN, SiCNC, and SiNCC.

A detailed investigation of the complex potential energy surface for the reaction of singlet methylene (CH2) with Nitrous oxide (N2O) using B3LYP/6-31G(d,p) and single point QCISD(T)/6-311G(d,p) methods is presented. This work can assist experiments to identify the products of the CH2+NO2 reaction.

The complex singlet potential energy surface of the CHNO2 system is investigated to explore the possible reaction mechanism of CH radical with NO2. Possible energetically allowed reaction pathways leading to various low-lying dissociation products are obtained.

Hydrogen abstraction reactions of hydrogen atom with germane and silane were studied by using ab initio molecular orbital theory and canonical vibrational transition state theory. The reaction rate constants in the temperature range 200-2600 k are calculated by the canonical variational transition state theory (CVT) with small curvature tunneling (SCT) correlation.

Different density functional levels were employed to perform detailed theoretical studies of the ion-molecule reaction of [HCN.sup.+] with [C.sub.2][H.sub.2]. The large rate constant obtained for reaction between [HCN.sup.+] and [C.sub.2][H.sub.2] provide insight into the mechanism of [HCN.sup.+] toward other [pi]-bonded molecules.

The dual-level direct dynamics approach is employed to study the hydrogen abstraction reactions of the 1,1,2,2,3-fluorinated propane by using the hydroxyl radical. The variation rate and the small-curvature variational transition-state theory are shown to highly affect the rate constants of the system.

A series of ruthenium(II) complexes, [[Ru([H.sub.m]tcterpy)[(NCS).sub.3]].sup.n-] (m = 0, 1, 2, and 3; n = 4, 3, 2, and 1), are examined to explore their electronic structures and spectroscopic properties. The results have provided a direct insight into the origins of the transitions and their possible role in dye-sensitized solar cell injection dynamics, as well as the design of new and more efficient solar cells sensitizers.

The first principles calculations are used for studying the structures and stabilities of [([Al.sub.2][O.sub.3]).sub.n] (n = 1-10 and 30) clusters. The results have shown their potential uses for [H.sub.2] physisorption, indicating that [([Al.sub.2][O.sub.3]).sub.n] cages are valuable candidates as [H.sub.2] storage materials due to their physisorption property without barriers.

A detail study at computational level was conducted to understand the complex potential-energy surface related to the reaction between HC[N.sup.+] and C[H.sub.4]. The analogous ion-molecule reaction provides insight into the atmosphere on Titan, the largest satellite of Saturn which contains abundant neutral amount of C[H.sub.4] after nitrogen.