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Song K, Song H, Li J. Validating experiments for the reaction H 2 + NH 2- by dynamical calculations on an accurate full-dimensional potential energy surface. Phys Chem Chem Phys 2022; 24:10160-10167. [PMID: 35420091 DOI: 10.1039/d2cp00870j] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ion-molecule reactions play key roles in the field of ion related chemistry. As a prototypical multi-channel ion-molecule reaction, the reaction H2 + NH2- → NH3 + H- has been studied for decades. In this work, we develop a new globally accurate potential energy surface (PES) for the title system based on hundreds of thousands of sampled points over a wide dynamically relevant region that covers long-range interacting configuration space. The permutational invariant polynomial-neural network (PIP-NN) method is used for fitting and the resulting total root mean squared error (RMSE) is extremely small, 0.026 kcal mol-1. Extensive dynamical and kinetic calculations are carried out on this PIP-NN PES. Impressively, a unique phenomenon of significant reactivity suppression by exciting the rotational mode of H2 is reported, supported by both the quasi-classical trajectory (QCT) and quantum dynamics (QD) calculations. Further analysis uncovers that exciting the H2 rotational mode would prevent the formation of the reactant complex and thus suppress the reactivity. The calculated rate coefficients for H2/D2 + NH2- agree well with the experimental results, which show an inverse temperature dependence from 50 to 300 K, consistent with the capture nature of this barrierless reaction. The significant kinetic isotope effect observed by experiments is well reproduced by the QCT computations as well.
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Affiliation(s)
- Kaisheng Song
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, P. R. China.
| | - Hongwei Song
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
| | - Jun Li
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, P. R. China.
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2
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Pan M, Xiang H, Li Y, Song H. Study on the kinetics and dynamics of the H 2 + NH 2- reaction on a high-level ab initio potential energy surface. Phys Chem Chem Phys 2021; 23:17848-17855. [PMID: 34612274 DOI: 10.1039/d1cp02423j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gas-phase ion-molecule reactions play major roles in many fields of chemistry and physics. The reaction of an amino radical anion with a hydrogen molecule is one of the simplest proton transfer reactions involving anions. A globally accurate full-dimensional potential energy surface (PES) for the NH2- + H2 reaction is developed by the fundamental invariant-neural network method, resulting in a root mean square error of 0.116 kcal mol-1. Quasi-classical trajectory calculations are then carried out on the newly developed PES to give integral cross sections, differential cross sections and thermal rate coefficients. This reaction has two reaction channels, proton transfer and hydrogen exchange. The reactivity of the proton transfer channel is about one or two orders of magnitude stronger than that of the hydrogen exchange channel in the energy range studied. Vibrational excitation of H2 promotes the proton transfer reaction, while fundamental excitation of each vibrational mode of NH2- has a negligible effect. In addition, the theoretical rate coefficients of the proton transfer reaction on the PES show inverse temperature dependence from 150 to 750 K, in accordance with the available experimental results.
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Affiliation(s)
- Mengyi Pan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
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3
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Mohandas S, Ramabhadran RO, Kumar SS. Theoretical Investigation of a Vital Step in the Gas-Phase Formation of Interstellar Ammonia NH 2+ + H 2 → NH 3+ + H. J Phys Chem A 2020; 124:8373-8382. [PMID: 32870677 DOI: 10.1021/acs.jpca.0c05019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A crucial step in the gas-phase formation of ammonia in the interstellar medium (ISM) is the reaction of NH2+ with molecular hydrogen. Understanding the electronic structure of the participating species in this reaction and the evaluation of the rate coefficients at interstellar temperatures are, therefore, critical to gain new insights into the mechanisms of formation of interstellar ammonia. We present here the first theoretical results of the rate coefficients of this reaction as a function of temperatures relevant to the ISM, computed using transition-state theory. The results are in reasonable agreement with recent experimental data. This exothermic reaction features a tiny barrier which is primarily a consequence of zero-point energy corrections. The results demonstrate that quantum mechanical tunneling and core-electron correlations play significant roles in determining the rate of the reaction. The noteworthy failure of popular density functionals to describe this reaction is also highlighted.
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Affiliation(s)
- Salvi Mohandas
- Department of Physics, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507 Andhra Pradesh, India.,Center for Atomic, Molecular, and Optical Sciences & Technologies, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507 Andhra Pradesh, India
| | - Raghunath O Ramabhadran
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507 Andhra Pradesh, India.,Center for Atomic, Molecular, and Optical Sciences & Technologies, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507 Andhra Pradesh, India
| | - S Sunil Kumar
- Department of Physics, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507 Andhra Pradesh, India.,Center for Atomic, Molecular, and Optical Sciences & Technologies, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507 Andhra Pradesh, India
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4
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Yurtsever E, Satta M, Wester R, Gianturco FA. On the Formation of Interstellar CH - Anions: Exploring Mechanism and Rates for CH 2 Reacting with H . J Phys Chem A 2020; 124:5098-5108. [PMID: 32463233 PMCID: PMC7322726 DOI: 10.1021/acs.jpca.0c02412] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
We
present accurate ab initio calculations on the structural properties
of a gas-phase reaction of possible interest for Saturn’s outer
atmosphere chemistry, in which the CH2 molecule has been
detected. In the present study, that molecule is made to react with
the H– anion to form the CH– species,
one considered as a possible intermediate in ionic processes networks.
The results indicate that this reaction is markedly exothermic and
proceeds with the formation of an intermediate, which occurs via only
a shallow barrier below the reagents and progresses directly to the
product region. The corresponding rate coefficients of reactions are
also computed by making use of the variational transition state theory
modeling and found to efficiently lead to the formation of the final
anion even at the lower temperatures of interstellar medium conditions.
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Affiliation(s)
- E Yurtsever
- Department of Chemistry, Koc University, Rumelifeneri Yolu, Sariyer, TR, 34450 Istanbul, Turkey
| | - M Satta
- CNR-ISMN and Department of Chemistry, The University of Rome Sapienza, P.le A. Moro 5, 00185 Rome, Italy
| | - R Wester
- Institut für Ionen Physik und Angewandte Physik, Leopold-Franzens-Universität, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - F A Gianturco
- Institut für Ionen Physik und Angewandte Physik, Leopold-Franzens-Universität, Technikerstrasse 25, 6020 Innsbruck, Austria
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Satta M, Cartoni A, Catone D, Castrovilli MC, Bolognesi P, Zema N, Avaldi L. The Reaction of Sulfur Dioxide Radical Cation with Hydrogen and its Relevance in Solar Geoengineering Models. Chemphyschem 2020; 21:1146-1156. [PMID: 32203633 DOI: 10.1002/cphc.202000194] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 03/23/2020] [Indexed: 11/06/2022]
Abstract
SO2 has been proposed in solar geoengineering as a precursor of H2 SO4 aerosol, a cooling agent active in the stratosphere to contrast climate change. Atmospheric ionization sources can ionize SO2 into excited states of S O 2 · + , which quickly reacts with trace gases in the stratosphere. In this work we explore the reaction of H 2 D 2 with S O 2 · + excited by tunable synchrotron radiation, leading to H S O 2 + + H ( D S O 2 + + D ), where H contributes to O3 depletion and OH formation. Density Functional Theory and Variational Transition State Theory have been used to investigate the dynamics of the title barrierless and exothermic reaction. The present results suggest that solar geoengineering models should test the reactivity of S O 2 · + with major trace gases in the stratosphere, such as H2 since this is a relevant channel for the OH formation during the nighttime when there is not OH production by sunlight. OH oxides SO2 , triggering the chemical reactions leading to H2 SO4 aerosol.
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Affiliation(s)
- Mauro Satta
- ISMN (CNR) c/o Dipartimento di Chimica Sapienza Universita' di Roma, Pl.e Aldo Moro 5, Roma, Italy
| | - Antonella Cartoni
- Dipartimento di Chimica, Sapienza Universitá di Roma, Pl.e Aldo Moro 5, Roma, Italy
| | - Daniele Catone
- CNR-ISM, Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere, Roma, Italy
| | | | - Paola Bolognesi
- CNR-ISM, Area della Ricerca di Roma 1, Via Salaria Km 29,300, Monterotondo Scalo (RM), Italy
| | - Nicola Zema
- CNR-ISM, Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere, Roma, Italy
| | - Lorenzo Avaldi
- CNR-ISM, Area della Ricerca di Roma 1, Via Salaria Km 29,300, Monterotondo Scalo (RM), Italy
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