New ab initio potential energy surface and quantum dynamics of the reaction H(2S) + NH(X3Σ-) → N(4S) + H2.
ABSTRACT A new global potential energy surface is reported for the ground state ((4)A(")) of the reaction H((2)S) + NH(X(3)Σ(-)) → N((4)S) + H(2) from a set of accurate ab initio data, which were computed using the multi-reference configuration interaction with a basis set of aug-cc-pV5Z. The many-body expansion and neural network methods have been used to construct the new potential energy surface. The topographical features of the new global potential energy surface are presented. The predicted barrier height is lower than previous theoretical estimates and the heat of reaction with zero-point energy is closer to experimental results. The quantum reactive scattering dynamics calculation was carried out over a range of collision energies (0-1.0 eV) on the new potential energy surface. The reaction probabilities, integral cross-section, and rate constants for the title reaction were calculated. The calculated rate constants are in excellent agreement with the available experimental results.
- 01/1994; The MathWorks, Inc., Natick, MA..
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ABSTRACT: The rate coefficient of the reaction NH(X )+H()N()+H2(X ) is determined in a quasistatic laser-flash photolysis, laser-induced fluorescence system at low pressures (2 mbar ⩽ p ⩽ 10 mbar). The NH(X) radicals are produced via the quenching of NH(a) (obtained by photolyzing HN3) with Xe whereas the H atoms are generated in a H2/He microwave discharge. The NH(X) concentration profile is measured under pseudo-first-order condition, i.e., in the presence of a large excess of H atoms. The room temperature rate coefficient is determined to be k1a = (1.9±0.5)×1012 cm3 mol−1 s−1. It is found to be independent of the pressure in the range considered in the present experiment. A global potential energy surface for the state is calculated with the internally contracted multireference configuration interaction method and the augmented correlation consistent polarized valence quadruple zeta atomic basis. The title reaction is investigated by classical trajectory calculations on this surface. The theoretical room temperature rate coefficient is k1a = 0.92×1012cm3 mol−1 s−1. Using the thermodynamical data for the atoms and molecules involved, the rate coefficient for the reverse reaction, k−1a, is also calculated. At high temperatures it agrees well with the measured k−1a.The Journal of Chemical Physics 03/2005; 122(11):114301-114301-7. · 3.16 Impact Factor
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ABSTRACT: A single-sheeted DMBE potential energy surface is reported for the reactions N(4S)+H2<-->NH(X3Sigma-)+H based on a fit to accurate multireference configuration interaction energies. These have been calculated using the aug-cc-pVQZ basis set of Dunning and the full valence complete active space wave function as reference, being semi-empirically corrected by scaling the two-body and three-body dynamical correlation energies. The topographical features of the novel global potential energy surface are examined in detail, including a conical intersection involving the two first 4A'' potential energy surfaces which has been transformed into an avoided crossing in the present single-sheeted representation.Physical Chemistry Chemical Physics 08/2005; 7(15):2867-73. · 3.83 Impact Factor