# 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.

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**ABSTRACT:**New accurate potential energy surfaces (PESs) for the lowest states (3A″ and 3A′) of the O(3P) + H2 reaction are proposed using an ab initio multireference configuration interaction method (MRCI) with Davidson correction and a large orbital basis set (aug-cc-pv5z). The many-body expansion procedure is employed to describe the analytical PES function. The topographical features of the new global PESs are presented and compared with previous surfaces. The quantum reaction scattering dynamics calculations are carried out over the collision energies range of 0.3–1.0 eV on the new PESs. The integral cross-sections and rate coefficients for the title reaction were calculated. The calculated coefficients are lower than the experimental ones at the low temperature.Computational and Theoretical Chemistry 04/2012; 986:25–29. DOI:10.1016/j.comptc.2012.02.002 - [Show abstract] [Hide abstract]

**ABSTRACT:**In this work, quasi-classical trajectory (QCT) calculations have been first carried out for the title reaction on a new global potential energy surface for the lowest quartet electronic state, 4A″. The average rotational alignment factor [P 2( j' · k )] as a function of collision energy and the two commonly used polarization dependent generalized differential cross sections PDDCS00, PDDCS20, have been calculated in the center-of-mass (CM) frame, separately. Three angular distributions, P( r), P(φ r), and P( r, φ r) are also calculated to gain insight into the alignment and the orientation of the product molecules. Calculations show that the average rotational alignment factor on the ZH PES is almost invariant with collision energies. The distributions of P( r) and P(φ r) derived from the title reaction indicate that the product polarization is strong. Validity of the QCT calculation has been examined and proven in the comparison with the quantum-wave-packet calculation results. Comparisons with available quasi-classical trajectory results are made and discussed.Canadian Journal of Chemistry 01/2013; 91(6). DOI:10.1139/cjc-2012-0404 - [Show abstract] [Hide abstract]

**ABSTRACT:**The quasi-classical trajectory (QCT) is calculated to study the stereodynamics properties of the title reaction H(2S) + NH(X3 Σ−) → N(4S) + H2 on the ground state 4A'' potential energy surface (PES) constructed by Zhai and Han [2011 J. Chem. Phys. 135 104314]. The calculated QCT reaction probabilities and cross sections are in good agreement with the previous theoretical results. The effects of the collision energy on the k—k' distribution and the product polarization of H2 are studied in detail. It is found that the scattering direction of the product is strongly dependent on the collision energy. With the increase in the collision energy, the scattering directions of the products change from backward scattering to forward scattering. The distribution of P(θr) is strongly dependent on the collision energy below the lower collision energy (about 11.53 kcal/mol). In addition, the P(r) distribution dramatically changes as the collision energy increases. The calculated QCT results indicate that the collision energy plays an important role in determining the stereodynamics of the title reaction.Chinese Physics B 06/2013; 22(6):068201. DOI:10.1088/1674-1056/22/6/068201