A reliable computational method for the prediction of organoselenium geometries and bond dissociation energies (BDEs) has been determined on the basis of the performance of density functional theory (DFT: B3LYP and B3PW91) and ab initio molecular orbital procedures (Hartree-Fock (HF)) in conjunction with various Pople basis sets including (but not limited to) the 6-31G(d), 6-31G(d,p), 6-311G(d)...

We have studied how the calculation of electronic and vibrational contributions to nonlinear optical properties of three representative p-conjugated organic molecules is affected by the choice of basis set and the inclusion of electron correlation effects. The 6-31G basis does not always provide even qualitative accuracy. For semiquantitative accuracy a 6-311G(d) basis is sufficient. Although, ...

The occurrence of elemental mercury in flue gases from coal combustion is a problem of current environmental concern. Oxidized mercury species can be effectively removed from the flue gases by chemical scrubbers. However, the detailed mechanism by which oxidation occurs remains unclear. Theoretical rate constants are calculated for mercury oxidation by atomic chlorine. The potential energy surf...

Structures and electronic states of the HOO radical interacting with water molecules, expressed by HOO(H2O)n (n = 1 and 2), have been investigated by means of a direct ab initio molecular dynamics (MD) method. From the static ab initio calculation of HOO-H2O complex, two types of HOO radical were found: i.e., the HOO radical acts as a hydrogen donor or acceptor in the complex (n = 1). The bindi...

The correlation consistent composite approach (ccCA) was applied to the prediction of reaction barrier heights (i.e., transition state energy relative to reactants and products) for a standard benchmark set of reactions comprised of both hydrogen transfer reactions and nonhydrogen transfer reactions (i.e., heavy-atom transfer, SN2, and unimolecular reactions). The ccCA method was compared again...

This study examines a variety of compounds containing silicon-phosphorus multiple bonds as well as a selection of hydrogen-bridged species, including a doubly bridged structure. The structures of 29 minima and 37 transition states of the form Si2PHn (n ) 7, 5, 3, 1) have been optimized at the MP2(full)/6-31G(d) level of theory; a representative subset was also optimized at the QCISD/6-311G(d,p)...

Cálculos B3LYP usando bases até 6-311G(3d2f,3p2d) foram utilizados para a previsão acurada de propriedades termoquímicas relacionadas à reação de dissociação trans-HONO(XA’) HO(XP) + NO(X P). Um estudo sistemático da influência da base foi realizado e resultados B3LYP foram comparados a dados experimentais e a outros resultados teóricos, calculados usando os métodos G2, G2MP2, CBS e métodos ab ...

The understanding of the thermal decomposition chemistry chemical warfare nerve agents is largely limited by scarcity kinetic data. Because high toxicity these molecules, experimental determination their properties very difficult. In present work, a comprehensive detailed model for sarin and some simulants, i.e. di-isopropyl methyl phosphonate (DIMP), diethyl methylphosphonate (DEMP), triethyl ...

The microscopic origin and quantum effects of the low barrier hydrogen bond (LBHB) in the proton-bound ammonia dimer cation N(2)H(7) (+) were studied by means of ab initio and density-functional theory (DFT) methods. These results were analyzed in the framework of vibronic theory and compared to those obtained for the Zundel cation H(5)O(2) (+). All geometry optimizations carried out using wave...

      In this study, the interaction between NO2+ cation and Hen (n = 1-7) clusters is investigated by means of ab initio calculations at MP2/aug-cc-pVTZ and QCISD/aug-cc-pVTZ computational levels. The first and second solvation shells were obtained while N atom of NO2+ interacts with five and two He atoms, respectively. Stabilizat...