An experimental and theoretical study of the photoelectron spectrum of hydrogen selenide

AB INITIO CALCULATIONS AND KINETICS STUDY FOR THE DIRECT HYDROGEN ABSTRACTION REACTION OF HYDROGEN SELENIDE WITH HYDROGEN ATOM

We present a direct ab initio dynamics study of thermal rate constants of the hydrogen abstraction reaction of H 2 Se + H → SeH + H 2. The QCISD and CCSD(T) methods were employed to optimize the geometries of stationary points and to calculate the harmonic vibrational frequencies. The split-valence 6-311 + G(d,p) and correlation-consistent cc-pVTZ basis sets big enough to describe the geometries and vibrational frequencies of the species involving in the title reaction. The energies obtained at the QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) level of theory is able to compare to those calculated at the CCSD(T)/6-311 ++ G(3df,3pd)//CCSD(T)/6-311 + G(d,p) level of theory. The energies of all the selected points along the minimum energy path (MEP) were refined at the QCISD(T)/6-311 ++ G(3df,3pd) level of theory. The barriers were obtained at the both QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) and CCSD(T)/6-311 ++ G(3df,3pd)//CCSD(T)/6-311 + G(d,p) levels of theory are in good agreement with experimental one. The forward rate constants were evaluated with both canonical variational transition state theory with small curvature tunneling correction (CVT/SCT) and improved canonical variational transition state theory with small curvature tunneling correction (ICVT/SCT) in the temperature range of 200–2500 K. The calculated forward rate constants of the reaction at the QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) level of theory are in good agreement with available experimental data.

Interaction of coinage metal clusters with chalcogen dihydrides

The interaction of chalcogen dihydrides (H 2E; E = O, S, and Se) with small coinage metal clusters (M n ; M = Cu, Ag, and Au, n = 3 and 4) is studied based on density functional theory, with a focus on the nature of chalcogen-metal bonds. A newly developed pseudopotential-based correlation-consistent basis set is used for metal clusters together with the 6-311++G** basis set for the remaining atoms. Geometrical data identified that no significant deviation has been observed for molecules before and after complexation. For these three metals, binding energy calculations indicate that gold has the highest and silver has the lowest affinities for interaction with H 2E. In comparison with gold and copper, complexation between silver and chalcogen dihydrides is significantly weaker. It is found that interaction of H 2E molecules with the coinage metals have the order of H 2Se > H 2S > H 2O. Therefore, in agreement with experimental works, our calculations confirm that the gold-selenium bond is the most stable. The nature of M-E bonds is also interpreted by means of the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. According to the QTAIM results, the bonds are found to be partially ionic and partially covalent. Natural resonance theory (NRT) is used to calculate natural bond order and bond polarity. The NRT result indicates that the percentage of polarity of M-E bonds is affected by coinage metals.