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Espinosa-Garcia J, Rangel C. Analytical potential energy surface and dynamics for the OH + CH 3OH reaction. J Chem Phys 2023; 158:054302. [PMID: 36754788 DOI: 10.1063/5.0137372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Using as functional form a combination of valence bond and mechanic molecular terms a new full-dimensional potential energy surface was developed for the title reaction, named PES-2022, which was fitted to high-level ab initio calculations at the coupled-cluster singles, doubles, and perturbative triples-F12 explicitly correlated level on a representative number of points describing the reactive system. This surface simultaneously describes the two reaction channels, hydrogen abstraction from the methyl group [(R1) path] and from the alcohol group [(R2) path] of methanol to form water. PES-2022 is a smooth and continuous surface, which reasonably describes the topology of this reactive system from reactants to products, including the intermediate complexes present in the system. Based on PES-2022 an exhaustive dynamics study was performed using quasi-classical trajectory calculations under two different initial conditions: at a fixed room temperature, for direct comparison with the experimental evidence and at different collision energies, to analyze possible mechanisms of reaction. In the first case, the available energy was mostly deposited as water vibrational energy, with the vibrational population inverted in the stretching modes and not inverted in the bending modes, reproducing the experimental evidence. In the second case, the analysis of different dynamics magnitudes (excitation functions, product energy partitioning, and product scattering distributions), allows us to suggest different mechanisms for both (R1) and (R2) paths: a direct mechanism for the (R2) path vs an indirect one, related with "nearly trapped" trajectories in the intermediate complexes, for the (R1) path.
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Affiliation(s)
- J Espinosa-Garcia
- Área de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain
| | - C Rangel
- Área de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain
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Győri T, Czakó G. A comprehensive benchmark ab initio survey of the stationary points and products of the OH· + CH 3OH system. J Chem Phys 2023; 158:034301. [PMID: 36681627 DOI: 10.1063/5.0133978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Reactions between methanol and the hydroxyl radical are of significant interest for combustion-, atmospheric-, and astrochemistry. While the two primary product channels (the formation of H2O with either CH3O· or ·CH2OH) have been the subject of numerous studies, the possibility of other products has seen little attention. Here, we present a comprehensive thermochemical survey of the stationary points and plausible products of the reaction, featuring 29 geometries optimized at the UCCSD(T)-F12b/aug-cc-pVTZ level, followed by accurate composite ab initio computations for all stationary points (including ·CH2OH dissociation and isomerization) and five product channels, with a detailed evaluation of basis set convergence and efficiency. The computations reveal that the formation of methanediol and the hydroxymethoxy radical is thermodynamically favorable and the endothermicity of formaldehyde formation is low enough to be a plausible product channel. We also observe unexpectedly large energy deviations between the partially-spin-adapted ROHF-RCCSD(T) method and ROHF-UCCSD(T) as well as between UHF-UCCSDT(Q) and ROHF-UCCSDT(Q) results.
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Affiliation(s)
- Tibor Győri
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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Zhu Y, Zhao W, Jing B, Zhou J, Cai B, Li D, Ao Z. Density functional theory calculations on 2H-MoS2 monolayer for HCHO degradation: Piezoelectric-photocatalytic synergy. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.107816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Benitez Y, Nguyen TL, Parsons AJ, Stanton JF, Continetti RE. Probing the Exit Channel of the OH + CH 3OH → H 2O + CH 3O Reaction by Photodetachment of CH 3O -(H 2O). J Phys Chem Lett 2022; 13:142-148. [PMID: 34962408 DOI: 10.1021/acs.jpclett.1c03568] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Transition state dynamics of bimolecular reactions can be probed by photodetachment of a precursor anion when the Franck-Condon region of the corresponding neutral potential energy surface is near a saddle point. In this study, photodetachment of anions at m/z = 49 enabled investigation of the exit channel of the OH + CH3OH → H2O + CH3O reaction using photoelectron-photofragment coincidence spectroscopy. High-level coupled-cluster calculations of the stationary points on the anion surface show that the methoxide-water cluster CH3O-(H2O) is the stable minimum on the anion surface. Photodetachment at a 3.20 eV photon energy leads to long-lived H2O(CH3O) complexes and H2O + CH3O products consistent with both direct dissociative photodetachment and resonance mediated processes on the neutral surface. The partitioning of total kinetic energy in the system indicates that water stretch and bend excitation is induced in dissociative photodetachment and evidence for long-lived complexes consistent with vibrational Feshbach resonances is reported.
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Affiliation(s)
- Yanice Benitez
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - Thanh Lam Nguyen
- Quantum Theory Project, Department of Chemistry and Physics, University of Florida, Gainesville, Florida 32611, United States
| | - Austin J Parsons
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - John F Stanton
- Quantum Theory Project, Department of Chemistry and Physics, University of Florida, Gainesville, Florida 32611, United States
| | - Robert E Continetti
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
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Mazo-Sevillano PD, Aguado A, Roncero O. Neural network potential energy surface for the low temperature ring polymer molecular dynamics of the H 2CO + OH reaction. J Chem Phys 2021; 154:094305. [PMID: 33685156 DOI: 10.1063/5.0044009] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A new potential energy surface (PES) and dynamical study of the reactive process of H2CO + OH toward the formation of HCO + H2O and HCOOH + H are presented. In this work, a source of spurious long range interactions in symmetry adapted neural network (NN) schemes is identified, which prevents their direct application for low temperature dynamical studies. For this reason, a partition of the PES into a diabatic matrix plus a NN many-body term has been used, fitted with a novel artificial neural network scheme that prevents spurious asymptotic interactions. Quasi-classical trajectory (QCT) and ring polymer molecular dynamics (RPMD) studies have been carried on this PES to evaluate the rate constant temperature dependence for the different reactive processes, showing good agreement with the available experimental data. Of special interest is the analysis of the previously identified trapping mechanism in the RPMD study, which can be attributed to spurious resonances associated with excitations of the normal modes of the ring polymer.
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Affiliation(s)
- Pablo Del Mazo-Sevillano
- Unidad Asociada UAM-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias M-14, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Alfredo Aguado
- Unidad Asociada UAM-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias M-14, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Octavio Roncero
- Instituto de Física Fundamental (IFF-CSIC), CSIC, Serrano 123, 28006 Madrid, Spain
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Fang W, Winter P, Richardson JO. Microcanonical Tunneling Rates from Density-of-States Instanton Theory. J Chem Theory Comput 2020; 17:40-55. [PMID: 33351621 DOI: 10.1021/acs.jctc.0c01118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Semiclassical instanton theory is a form of quantum transition-state theory which can be applied to the computation of thermal reaction rates in complex molecular systems including quantum tunneling effects. There have been a number of attempts to extend the theory to treat microcanonical rates. However, the previous formulations are either computationally unfeasible for large systems due to an explicit sum over states or they involve extra approximations, which make them less reliable. We propose a robust and practical microcanonical formulation called density-of-states instanton theory, which avoids the sum over states altogether. In line with the semiclassical approximations inherent to the instanton approach, we employ the stationary-phase approximation to the inverse Laplace transform to obtain the densities of states. This can be evaluated using only post-processing of the data available from a small set of instanton calculations, such that our approach remains computationally efficient. We show that the new formulation predicts results that agree well with quantum scattering theory for an atom-diatom reaction and with experiments for a photoexcited unimolecular hydrogen transfer in a Criegee intermediate. When the thermal rate is evaluated from a Boltzmann average over our new microcanonical formalism, it can overcome some problems of conventional instanton theory. In particular, it predicts a smooth transition at the crossover temperature and is able to describe bimolecular reactions with pre-reactive complexes such as CH3OH + OH.
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Affiliation(s)
- Wei Fang
- Laboratory of Physical Chemistry, ETH Zürich, 8093 Zürich, Switzerland
| | - Pierre Winter
- Laboratory of Physical Chemistry, ETH Zürich, 8093 Zürich, Switzerland
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Novikov IS, Shapeev AV, Suleimanov YV. Ring polymer molecular dynamics and active learning of moment tensor potential for gas-phase barrierless reactions: Application to S + H2. J Chem Phys 2019; 151:224105. [DOI: 10.1063/1.5127561] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ivan S. Novikov
- Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, Nobel St. 3, Moscow 143026, Russia
| | - Alexander V. Shapeev
- Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, Nobel St. 3, Moscow 143026, Russia
| | - Yury V. Suleimanov
- Computation-Based Science and Technology Research Center, Cyprus Institute, 20 Kavafi Street, Nicosia 2121, Cyprus
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Bulut N, Aguado A, Sanz-Sanz C, Roncero O. Quantum Effects on the D + H 3+ → H 2D + + H Deuteration Reaction and Isotopic Variants. J Phys Chem A 2019; 123:8766-8775. [PMID: 31545608 DOI: 10.1021/acs.jpca.9b06081] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The title reaction and its isotopic variants are studied using quasi-classical trajectory (QCT) (without taking into account corrections to account for the possible zero point energy breakdown) and ring polymer molecular dynamics (RPMD) methods with a full dimensional and accurate potential energy surface which presents an exchange barrier of approximately 0.144 eV. The QCT rate constant increases when the temperature decreases from 1500 to 10 K. On the contrary, the RPMD rate constant decreases with decreasing temperature, in semiquantitative agreement with recent experimental results. The present RPMD results are in between the thermal and translational experimental rate constants, extracted from the measured data to eliminate the initial vibrational excitation of H3+, obtained in an arc discharge. The difference between the present RPMD results and experimental values is attributed to the possible existence of non thermal vibrational excitation of H3+, not completely removed by the semiempirical model used for the analysis of the experimental results. Also, it is found that, below 200 K, the RPMD trajectories are trapped, forming long-lived collision complexes, with lifetimes longer than 1 ns. These collision complexes can fragment by either redissociating back to reactants or react to products, in the two cases tunneling through the centrifugal and reaction barriers, respectively. The contribution of the formation of the complex to the total deuteration rate should be calculated with more accurate quantum methods, as has been found recently for reactions of larger systems, and the present four atoms system is a good candidate to benchmark the adequacy of RPMD method at temperatures below 100 K.
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Affiliation(s)
- Niyazi Bulut
- Department of Physics , Firat University , 23169 Elazig , Turkey
| | - Alfredo Aguado
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias, Módulo 14 , Universidad Autónoma de Madrid , 28049 , Madrid , Spain
| | - Cristina Sanz-Sanz
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias, Módulo 14 , Universidad Autónoma de Madrid , 28049 , Madrid , Spain
| | - Octavio Roncero
- Instituto de Física Fundamental (IFF-CSIC), C.S.I.C. , Serrano 123 , 28006 Madrid , Spain
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