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Title: A full-dimensional quantum dynamics study of the mode specificity in the H + HOD abstraction reaction

Abstract

We employ the initial state-selected time-dependent wave packet approach to an atom-triatom reaction to study the H + HOD → OH + HD/OD + H{sub 2} reaction without the centrifugal sudden approximation, based on an accurate potential energy surface which was recently developed by neural network fitting to high level ab initio energy points. The total reaction probabilities and integral cross sections, which are the exact coupled-channel results, are calculated for the HOD reactant initially in the ground and several vibrationally excited states, including the bending excited state, OD stretching excited states, OH stretching excited states, and combined excitations of them. The reactivity enhancements from different initial states of HOD are presented, which feature strong bond-selective effects of the reaction dynamics. The current results for the product branching ratios, reactivity enhancements, and relative cross sections are largely improved over the previous calculations, in quantitatively good agreement with experiment. The thermal rate constant for the title reaction and the contributions from individual vibrational states of HOD are also obtained.

Authors:
;  [1]
  1. State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)
Publication Date:
OSTI Identifier:
22416115
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ATOMS; BRANCHING RATIO; COUPLED CHANNEL THEORY; EXCITATION; HEAVY WATER; HYDROGEN; INTEGRAL CROSS SECTIONS; NEURAL NETWORKS; POTENTIAL ENERGY; PROBABILITY; REACTION KINETICS; REACTIVITY; SPECIFICITY; SUDDEN APPROXIMATION; TIME DEPENDENCE; VIBRATIONAL STATES; WAVE PACKETS

Citation Formats

Fu, Bina, E-mail: bina@dicp.ac.cn, and Zhang, Dong H., E-mail: zhangdh@dicp.ac.cn. A full-dimensional quantum dynamics study of the mode specificity in the H + HOD abstraction reaction. United States: N. p., 2015. Web. doi:10.1063/1.4907918.
Fu, Bina, E-mail: bina@dicp.ac.cn, & Zhang, Dong H., E-mail: zhangdh@dicp.ac.cn. A full-dimensional quantum dynamics study of the mode specificity in the H + HOD abstraction reaction. United States. doi:10.1063/1.4907918.
Fu, Bina, E-mail: bina@dicp.ac.cn, and Zhang, Dong H., E-mail: zhangdh@dicp.ac.cn. Sat . "A full-dimensional quantum dynamics study of the mode specificity in the H + HOD abstraction reaction". United States. doi:10.1063/1.4907918.
@article{osti_22416115,
title = {A full-dimensional quantum dynamics study of the mode specificity in the H + HOD abstraction reaction},
author = {Fu, Bina, E-mail: bina@dicp.ac.cn and Zhang, Dong H., E-mail: zhangdh@dicp.ac.cn},
abstractNote = {We employ the initial state-selected time-dependent wave packet approach to an atom-triatom reaction to study the H + HOD → OH + HD/OD + H{sub 2} reaction without the centrifugal sudden approximation, based on an accurate potential energy surface which was recently developed by neural network fitting to high level ab initio energy points. The total reaction probabilities and integral cross sections, which are the exact coupled-channel results, are calculated for the HOD reactant initially in the ground and several vibrationally excited states, including the bending excited state, OD stretching excited states, OH stretching excited states, and combined excitations of them. The reactivity enhancements from different initial states of HOD are presented, which feature strong bond-selective effects of the reaction dynamics. The current results for the product branching ratios, reactivity enhancements, and relative cross sections are largely improved over the previous calculations, in quantitatively good agreement with experiment. The thermal rate constant for the title reaction and the contributions from individual vibrational states of HOD are also obtained.},
doi = {10.1063/1.4907918},
journal = {Journal of Chemical Physics},
number = 6,
volume = 142,
place = {United States},
year = {Sat Feb 14 00:00:00 EST 2015},
month = {Sat Feb 14 00:00:00 EST 2015}
}
  • Dynamics of the title reaction is investigated on an ab initio based potential energy surface using a full-dimensional quantum wave packet method within the centrifugal sudden approximation. It is shown that the reaction between H and HCN leads to both the hydrogen exchange and hydrogen abstraction channels. The exchange channel has a lower threshold and larger cross section than the abstraction channel. It also has more oscillations due apparently to quantum resonances. Both channels are affected by long-lived resonances supported by potential wells. Comparison with experimental cross sections indicates underestimation of the abstraction barrier height.
  • This work performs a time-dependent wavepacket study of the H{sub 2} + C{sub 2}H → H + C{sub 2}H{sub 2} reaction on a new ab initio potential energy surface (PES). The PES is constructed using neural network method based on 68 478 geometries with energies calculated at UCCSD(T)-F12a/aug-cc-pVTZ level and covers H{sub 2} + C{sub 2}H↔H + C{sub 2}H{sub 2}, H + C{sub 2}H{sub 2} → HCCH{sub 2}, and HCCH{sub 2} radial isomerization reaction regions. The reaction dynamics of H{sub 2} + C{sub 2}H → H + C{sub 2}H{sub 2} are investigated using full-dimensional quantum dynamics method. The initial-state selected reactionmore » probabilities are calculated for reactants in eight vibrational states. The calculated results showed that the H{sub 2} vibrational excitation predominantly enhances the reactivity while the excitation of bending mode of C{sub 2}H slightly inhibits the reaction. The excitations of two stretching modes of C{sub 2}H molecule have negligible effect on the reactivity. The integral cross section is calculated with J-shift approximation and the mode selectivity in this reaction is discussed. The rate constants over 200-2000 K are calculated and agree well with the experimental measured values.« less
  • We present approximate quantum calculations of cumulative reaction probabilities, rotationally averaged cross sections, and branching ratios for the reactions H+HOD and H+H[sub 2]O, using the Walch--Dunning--Schatz--Elgersma potential. The calculations are done using the reduced dimensionality, adiabatic-bend approach in which the three internal bending degrees of freedom are treated adiabatically. The H+HOD calculations focus primarily on the effect of vibrationally exciting the OH or OD local modes of HOD on the reactivity, the branching ratios to form the products HD+OH and H[sub 2]+OD, and their final vibrational state distributions. The calculations of the H+H[sub 2]O reaction focus on two initial vibrationalmore » states, one with three quanta of vibrational excitation in the local mode stretch, and one with two quanta in one local mode and one quantum in the other local mode. The results are generally in good agreement with experiments and previous calculations.« less
  • An initial state selected time-dependent wave packet method is applied to study the dynamics of the OH + CHD{sub 3} reaction with a six-dimensional model on a newly developed full-dimensional ab initio potential energy surface (PES). This quantum dynamical (QD) study is complemented by full-dimensional quasi-classical trajectory (QCT) calculations on the same PES. The QD results indicate that both translational energy and the excitation of the CH stretching mode significantly promote the reaction while the excitation of the umbrella mode has a negligible effect on the reactivity. For this early barrier reaction, interestingly, the CH stretching mode is more effectivemore » than translational energy in promoting the reaction except at very low collision energies. These QD observations are supported by QCT results. The higher efficacy of the CH stretching model in promoting this early barrier reaction is inconsistent with the prediction of the naively extended Polanyi’s rules, but can be rationalized by the recently proposed sudden vector projection model.« less