A direct ab initio dynamics study is presented on two channels of the gas-phase reaction of the hydrogen atom with formyl chloride, HCOCl. The geometries, harmonic vibrational frequencies, energies, and enthalpies of all of the stationary points are calculated at the BHandHLYP, MP2, and QCISD levels of theory with the cc-pVDZ basis set. The minimum energy paths (MEPs) of both channels of the title reaction are also computed with the same methods and basis set. The energies of stationary points and the points along the MEP for each channel are refined by means of some single-point multilevel energy calculations (HL). The rate constants are evaluated with the conventional transition state theory (TST), the improved canonical varitional transition state theory (ICVT), and the improved canonical varitional transition state theory with small-curvature tunneling correction (ICVT/SCT) in the temperature range of 300-2500K. The fitted Arrhenius expressions of the calculated ICVT/SCT rate constants at the HL//BHandHLYP/cc-pVDZ and HL//QCISD/cc-pVDZ levels of theory are k1 ICVT/SCT(T)=1.16

2-compounds M2N4 (M) Li, Na, K, Rb, or Cs) have been examined with ab initio and density functional theory (DFT) methods. To our knowledge, these compounds, except for the D4h bipyramidal Li2N4, are first reported here. The bipyramidal structures with two metal cations above and below the N4 2- plane are global minima for all five M2N4 systems. Kinetic analysis shows that the bipyramidal M2N4 species may exist or be characterized due to their significant isomerization or dissociation barriers (39.2-48.6 kcal/mol). Nucleus-independent chemical shifts (NICSs) criteria and the presence of six delocalized

Two new isomers of N12 clusters were reported in addition to the four isomers previously studied. The decomposition pathways of these six N12 isomers were studied by using the density functional theory (DFT) method at the B3LYP/6-31G* level. Relative energies were further calculated at the B3LYP/6-311+G(3df, 2p)//B3LYP/6-31G* level. DFT predicts that the dissociation of diazobispentazole proceeds via ring breaking and the barrier height is only 4.0kcal/mol at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G* level. The dissociation reaction of N12 consisting of an aromatic N5 ring and a N7 open chain prefers ring breaking, at a cost of 9.2kcal/mol, to breaking a bond in the side chain. For open-chain N12 (C2h) isomer, the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G* barrier height for the N2 elimination reaction is 14.5kcal/mol. As for the cyclic and cagelike isomers, their decomposition barrier heights are all much lower than 10kcal/mol. From the results presented here, it seems that these six isomers are not kinetically stable enough because of their lower barrier heights of decomposition.

The two reactions of acetonitrile with atomic chlorine and bromine have been studied using the density functional theory method. By comparing with the available experimental data and quadratic configuration interaction results, the combination of the hybrid Becke's half-and-half method for nonlocal exchange and the Lee-Yang-Parr nonlocal correlation functional method (BH&HLYP) with the 6-311G(d, p) basis set is settled on the minimum energy paths calculations for the two reactions. Barrier heights for the two forward reactions are predicted theoretically to be 5.36 and 13.03 kcal mol-1 at the BH&HLYP/6-311++G(3df, 2p)//BH&HLYP/6-311G(d, p) level, respectively. The canonical variational transition state theory incorporating the zero-curvature tunneling and small-curvature tunneling corrections using the general polyatomic rate constant code Polyrate-8.2 was used to predict the rate constants of the two reactions. The calculated rate constants and the activation energies for the reaction of acetonitrile with chlorine atom are in satisfactory agreement with the experimental data in the temperature range from 250 to 723K.

A systematic investigation of Ge2Fn/Ge2F n systems was carried out with five density functional theory (DFT) methods in conjunction withDZP basis sets. For eachcompoun d various structures, including minima, transition states and other energetically low lying stationary points, were optimized. The geometries and relative energies are discussed and compared. Adiabatic electron affinities, vertical electron affinities and anion vertical detachment energies are reported. Three types of dissociation energies pertaining to the global minima for each compound are reported. The theoretical predictions are in good agreement with the limited available experimental results. Many unusual structural features are predicted for these systems. Neutral Ge2F is predicted to have a bridged C2v structure, while its anion is very floppy, with the bridged structure very slightly favoured. The Ge2F2 molecule is predicted to have the butterfly structure known from experiment for Si2H2, while the Ge2F 3 ion has a trans-bent structure. Ge2F3 is predicted to have an unprecedented FGe-F-GeF structure withno Ge Ge bond, while its anion has a somewhat more conventional monobridged structure, analogous to that of the nonclassical vinyl cation. Neutral Ge2F4 has a dibridged structure of C2h symmetry, while its anion has a trans-bent structure with a very long Ge Ge bond. The Ge2F5 molecule is doubly bridged and has no Ge Ge bond, while the anion is of the type F2Ge-F-GeF2 , again withno Ge Ge bond. Ge2F6 has the anticipated ethane structure, as does its anion, but witha very long Ge Ge bond. The adiabatic electron affinities (EAad) are predicted to be 2.12 (Ge2F), 2.03 (Ge2F2), 2.02 (Ge2F3), 1.64 (Ge2F4), 4.57 (Ge2F5), and 2.66 eV (Ge2F6), respectively, by the BHLYP method, which is regarded as the best method in the present paper for predicting EAs. Comparisons with the analogous C2Fn and Si2Fn systems reveals some interesting trends and differences. For example, while C2F6 will not capture an electron, Si2F6 is predicted to have small electron affinity (0.73 eV), while that of Ge2F6 is substantial. The same trend to larger EAs on going down the Periodic Table is seen for the X2F5 systems, with1.77 (C2F5), 2.68 (Si2F5), and 4.57 eV (Ge2F5). However, the EAs do not follow a monotonic trend for the X2F, X2F3 and X2F4 systems withrespect to the series X C, Si, Ge.