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Tu Z, Li J, Yang M, Chen Y, Wang Y, Song H. Accurate ab initio based potential energy surface and kinetics of the Cl + NH3 → HCl + NH2 reaction. J Chem Phys 2024; 161:034304. [PMID: 39007384 DOI: 10.1063/5.0216562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Accepted: 07/01/2024] [Indexed: 07/16/2024] Open
Abstract
The gas-phase reaction Cl + NH3 → HCl + NH2 is a prototypical hydrogen abstraction reaction, whose minimum energy path involves several intermediate complexes. In this work, a full-dimensional, spin-orbit corrected potential energy surface (SOC PES) is constructed for the ground electronic state of the Cl + NH3 reaction. About 52 000 energy points are sampled and calculated at the UCCSD(T)-F12a/aug-cc-pVTZ level, in which the data points located in the entrance channel are spin-orbit corrected. The spin-orbit corrections are predicted by a fitted three-dimensional energy surface from about 7520 energy points in the entrance channel at the level of CASSCF (15e, 11o)/aug-cc-pVTZ. The fundamental-invariant neural network method is utilized to fit the SOC PES, resulting in a total root mean square error of 0.12 kcal mol-1. The calculated thermal rate constants of the Cl + NH3 → HCl + NH2 reaction on the SOC PES with the soft-zero-point energy constraint agree reasonably well with the available experimental values.
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Affiliation(s)
- Zhao Tu
- School of Chemical and Environmental Engineering, Hubei Minzu University, Enshi 445000, China
- State Key Laboratory of Magnetic Resonance Spectroscopy and Imaging, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Jiaqi Li
- State Key Laboratory of Magnetic Resonance Spectroscopy and Imaging, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
- College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, China
| | - Mingjuan Yang
- State Key Laboratory of Magnetic Resonance Spectroscopy and Imaging, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Yizhuo Chen
- State Key Laboratory of Magnetic Resonance Spectroscopy and Imaging, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
- College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, China
| | - Yan Wang
- School of Chemical and Environmental Engineering, Hubei Minzu University, Enshi 445000, China
| | - Hongwei Song
- State Key Laboratory of Magnetic Resonance Spectroscopy and Imaging, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
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Horváth K, Tajti V, Papp D, Czakó G. Dynamics of the HCl + C 2H 5 Multichannel Reaction on a Full-Dimensional Ab Initio Potential Energy Surface. J Phys Chem A 2024; 128:4474-4482. [PMID: 38807530 PMCID: PMC11163425 DOI: 10.1021/acs.jpca.4c02042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/13/2024] [Accepted: 05/15/2024] [Indexed: 05/30/2024]
Abstract
We report a full-dimensional ab initio analytical potential energy surface (PES), which accurately describes the HCl + C2H5 multichannel reaction. The new PES is developed by iteratively adding selected configurations along HCl + C2H5 quasi-classical trajectories (QCTs), thereby improving our previous Cl(2P3/2) + C2H6 PES using the Robosurfer program package. QCT simulations for the H'Cl + C2H5 reaction reveal hydrogen-abstraction, chlorine-abstraction, and hydrogen-exchange channels leading to Cl + C2H5H', H' + C2H5Cl, and HCl + C2H4H', respectively. Hydrogen abstraction dominates in the collision energy (Ecoll) range of 1-80 kcal/mol and proceeds with indirect isotropic scattering at low Ecoll and forward-scattered direct stripping at high Ecoll. Chlorine abstraction opens around 40 kcal/mol collision energy and becomes competitive with hydrogen abstraction at Ecoll = 80 kcal/mol. A restricted opening of the cone of acceptance in the Cl-abstraction reaction is found to result in the preference for a backward-scattering direct-rebound mechanism at all energies studied. Initial attack-angle distributions show mainly side-on collision preference of C2H5 for both abstraction reactions, and in the case of the HCl reactant, H/Cl-side preference for the H/Cl abstraction. For hydrogen abstraction, the collision energy transfer into the product translational and internal energy is almost equally significant, whereas in the case of chlorine abstraction, most of the available energy goes into the internal degrees of freedom. Hydrogen exchange is a minor channel with nearly constant reactivity in the Ecoll range of 10-80 kcal/mol.
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Affiliation(s)
- Kitti Horváth
- 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
| | - Viktor Tajti
- 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
| | - Dóra Papp
- 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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3
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Czakó G, Gruber B, Papp D, Tajti V, Tasi DA, Yin C. First-principles mode-specific reaction dynamics. Phys Chem Chem Phys 2024; 26:15818-15830. [PMID: 38639072 DOI: 10.1039/d4cp00417e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Controlling the outcome of chemical reactions by exciting specific vibrational and/or rotational modes of the reactants is one of the major goals of modern reaction dynamics studies. In the present Perspective, we focus on first-principles vibrational and rotational mode-specific dynamics computations on reactions of neutral and anionic systems beyond six atoms such as X + C2H6 [X = F, Cl, OH], HX + C2H5 [X = Br, I], OH- + CH3I, and F- + CH3CH2Cl. The dynamics simulations utilize high-level ab initio analytical potential energy surfaces and the quasi-classical trajectory method. Besides initial state specificity and the validity of the Polanyi rules, mode-specific vibrational-state assignment for polyatomic product species using normal-mode analysis and Gaussian binning is also discussed and compared with experiment.
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Affiliation(s)
- 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.
| | - Balázs Gruber
- 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.
| | - Dóra Papp
- 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.
| | - Viktor Tajti
- 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.
| | - Domonkos A Tasi
- 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.
| | - Cangtao Yin
- 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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4
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Fu B, Zhang DH. Accurate fundamental invariant-neural network representation of ab initio potential energy surfaces. Natl Sci Rev 2023; 10:nwad321. [PMID: 38274241 PMCID: PMC10808953 DOI: 10.1093/nsr/nwad321] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 11/01/2023] [Accepted: 11/02/2023] [Indexed: 01/27/2024] Open
Abstract
Highly accurate potential energy surfaces are critically important for chemical reaction dynamics. The large number of degrees of freedom and the intricate symmetry adaption pose a big challenge to accurately representing potential energy surfaces (PESs) for polyatomic reactions. Recently, our group has made substantial progress in this direction by developing the fundamental invariant-neural network (FI-NN) approach. Here, we review these advances, demonstrating that the FI-NN approach can represent highly accurate, global, full-dimensional PESs for reactive systems with even more than 10 atoms. These multi-channel reactions typically involve many intermediates, transition states, and products. The complexity and ruggedness of this potential energy landscape present even greater challenges for full-dimensional PES representation. These PESs exhibit a high level of complexity, molecular size, and accuracy of fit. Dynamics simulations based on these PESs have unveiled intriguing and novel reaction mechanisms, providing deep insights into the intricate dynamics involved in combustion, atmospheric, and organic chemistry.
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Affiliation(s)
- Bina Fu
- 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
- Hefei National Laboratory, Hefei 230088, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dong H Zhang
- 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
- Hefei National Laboratory, Hefei 230088, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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5
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Szűcs T, Czakó G. Benchmark ab initio potential energy surface mapping of the F + CH 3NH 2 reaction. Phys Chem Chem Phys 2022; 24:20249-20257. [PMID: 35975600 DOI: 10.1039/d2cp03006c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This electronic structure study reveals four exothermic and two endothermic reaction pathways of the F + CH3NH2 system: the barrierless hydrogen abstraction from the methyl/amino group (HF + CH2NH2/CH3NH), amino/methyl substitution (NH2 + CH3F and CH3 + NH2F) and hydrogen substitution from the two functional groups (H + CH2FNH2/CH3NHF). The benchmark classical and adiabatic energies are obtained using a high-accuracy composite ab initio approach, where the gold-standard explicitly-correlated coupled cluster method (CCSD(T)-F12b) is applied with the correlation-consistent polarized valence quintuple-zeta F12 basis set (cc-pV5Z-F12) and further additive energy contributions. Considering indispensable post-(T) correlation, core correlation, scalar relativistic, spin-orbit and harmonic zero-point energy corrections, the obtained global minimum of the potential energy surface is the post-reaction CH2NH2⋯HF complex in the product channel. Although each substitution pathway has a high barrier, the energies of amino-substitution and methyl-hydrogen-substitution products are below the energy of the reactants, as well as the submerged-barrier hydrogen-abstraction pathways.
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Affiliation(s)
- Tímea Szűcs
- 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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6
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Gruber B, Tajti V, Czako G. Full-dimensional automated potential energy surface development and dynamics for the OH + C 2H 6 reaction. J Chem Phys 2022; 157:074307. [DOI: 10.1063/5.0104889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We develop a full-dimensional analytical potential energy surface (PES) for the OH + C2H6 reaction using the Robosurfer program system, which automatically (1) selects geometries from quasi-classical trajectories, (2) performs ab initio computations using a CCSD(T)-F12/triple-zeta-quality composite method, (3) fits the energies utilizing the permutationally-invariant monomial symmetrization approach, and iteratively improves the PES via steps (1)−(3). Quasi-classical trajectory simulations on the new PES reveal that hydrogen abstraction leading to H2O + C2H5 dominates in the collision energy range of 10−50 kcal/mol. The abstraction cross sections increase and the dominant mechanism shifts from rebound (small impact parameters and backward scattering) to stripping (larger impact parameters and forward scattering) with increasing collision energy as opacity functions and scattering angle distributions indicate. The abstraction reaction clearly favors side-on OH attack over O-side and the least-preferred H-side approach, whereas C2H6 behaves like a spherical object with only slight C−C-perpendicular side-on preference. Collision energy efficiently flows into the relative translation of the products, whereas product internal energy distributions show only little collision energy dependence. H2O/C2H5 vibrational distributions slightly/significantly violate zero-point energy and are nearly independent of collision energy, whereas the rotational distributions clearly blue-shift as collision energy increases.
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Affiliation(s)
- Balázs Gruber
- University of Szeged Faculty of Science and Informatics, Hungary
| | - Viktor Tajti
- Chemistry, University of Szeged Faculty of Science and Informatics, Hungary
| | - Gabor Czako
- Chemistry, University of Szeged Faculty of Science and Informatics, Hungary
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Espinosa-Garcia J, Rangel C, Corchado JC. Current Status of the X + C 2H 6 [X ≡ H, F( 2P), Cl( 2P), O( 3P), OH] Hydrogen Abstraction Reactions: A Theoretical Review. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27123773. [PMID: 35744901 PMCID: PMC9228020 DOI: 10.3390/molecules27123773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/08/2022] [Accepted: 06/08/2022] [Indexed: 12/03/2022]
Abstract
This paper is a detailed review of the chemistry of medium-size reactive systems using the following hydrogen abstraction reactions with ethane, X + C2H6 → HX + C2H5; X ≡ H, F(2P), Cl(2P), O(3P) and OH, and focusing attention mainly on the theoretical developments. These bimolecular reactions range from exothermic to endothermic systems and from barrierless to high classical barriers of activation. Thus, the topography of the reactive systems changes from reaction to reaction with the presence or not of stabilized intermediate complexes in the entrance and exit channels. The review begins with some reflections on the inherent problems in the theory/experiment comparison. When one compares kinetics or dynamics theoretical results with experimental measures, one is testing both the potential energy surface describing the nuclei motion and the kinetics or dynamics method used. Discrepancies in the comparison may be due to inaccuracies of the surface, limitations of the kinetics or dynamics methods, and experimental uncertainties that also cannot be ruled out. The paper continues with a detailed review of some bimolecular reactions with ethane, beginning with the reactions with hydrogen atoms. The reactions with halogens present a challenge owing to the presence of stabilized intermediate complexes in the entrance and exit channels and the influence of the spin-orbit states on reactivity. Reactions with O(3P) atoms lead to three surfaces, which is an additional difficulty in the theoretical study. Finally, the reactions with the hydroxyl radical correspond to a reactive system with ten atoms and twenty-four degrees of freedom. Throughout this review, different strategies in the development of analytical potential energy surfaces describing these bimolecular reactions have been critically analyzed, showing their advantages and limitations. These surfaces are fitted to a large number of ab initio calculations, and we found that a huge number of calculations leads to accurate surfaces, but this information does not guarantee that the kinetics and dynamics results match the experimental measurements.
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Győri T, Czako G. ManyHF: A pragmatic automated method of finding lower-energy Hartree−Fock solutions for potential energy surface development. J Chem Phys 2022; 156:071101. [DOI: 10.1063/5.0080817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Tibor Győri
- Chemistry, University of Szeged Faculty of Science and Informatics, Hungary
| | - Gabor Czako
- Chemistry, University of Szeged Faculty of Science and Informatics, Hungary
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9
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Gao D, Wang D. Time-dependent quantum dynamics study of the F + C 2H 6 → HF + C 2H 5 reaction. Phys Chem Chem Phys 2021; 23:26911-26918. [PMID: 34825679 DOI: 10.1039/d1cp04212b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction probabilities, integral cross sections, energy efficiency and rate constants are investigated for the F + C2H6 reaction using the quantum reaction dynamics, wave packet method. The ground-state integral cross section calculated using a six-degree-of-freedom approach is in very good agreement with the quasi-classical trajectory results. We find that the H-CH2CH3 stretching motion has the largest enhancement to reactivity, followed by the H-CH2-CH3 bending motion. However, the stretching motion between CH2 and CH3 slightly hinders the reactivity. The energy-form efficacy based on an equal amount of total energy shows that translational energy is more effective in enhancing the reactivity than vibrational energy of the H-CH2CH3 stretching motion at a relatively lower translational energy, while the reverse is true at a relatively high translational energy. An energy-shifting method is employed to calculate the full-dimensional rate constants. The quantum rate constants agree well with one of the two main experimental measurements, and the activation energy has an excellent agreement with the one calculated using canonical variational transition-state theory.
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Affiliation(s)
- Delu Gao
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, Shandong, China.
| | - Dunyou Wang
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, Shandong, China.
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10
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Papp D, Czakó G. Vibrational mode-specific dynamics of the F( 2P 3/2) + C 2H 6 → HF + C 2H 5 reaction. J Chem Phys 2021; 155:154302. [PMID: 34686045 DOI: 10.1063/5.0069658] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the competing effect of vibrational and translational excitation and the validity of the Polanyi rules in the early- and negative-barrier F(2P3/2) + C2H6 → HF + C2H5 reaction by performing quasi-classical dynamics simulations on a recently developed full-dimensional multi-reference analytical potential energy surface. The effect of five normal-mode excitations of ethane on the reactivity, the mechanism, and the post-reaction energy flow is followed through a wide range of collision energies. Promoting effects of vibrational excitations and interaction time, related to the slightly submerged barrier, are found to be suppressed by the early-barrier-induced translational enhancement, in contrast to the slightly late-barrier Cl + C2H6 reaction. The excess vibrational energy mostly converts into ethyl internal excitation while collision energy is transformed into product separation. The substantial reaction energy excites the HF vibration, which tends to show mode-specificity and translational energy dependence as well. With increasing collision energy, direct stripping becomes dominant over the direct rebound and indirect mechanisms, being basically independent of reactant excitation.
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Affiliation(s)
- Dóra Papp
- 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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11
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Tajti V, Győri T, Czakó G. Detailed quasiclassical dynamics of the F - + CH 3Br reaction on an ab initio analytical potential energy surface. J Chem Phys 2021; 155:124301. [PMID: 34598562 DOI: 10.1063/5.0065209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Dynamics and mechanisms of the F- + CH3Br(v = 0) → Br- + CH3F (SN2 via Walden inversion, front-side attack, and double inversion), F- + inverted-CH3Br (induced inversion), HF + CH2Br- (proton abstraction), and FH⋯Br- + 1CH2 reactions are investigated using a high-level global ab initio potential energy surface, the quasiclassical trajectory method, as well as non-standard configuration- and mode-specific analysis techniques. A vector-projection method is used to identify inversion and retention trajectories; then, a transition-state-attack-angle-based approach unambiguously separates the front-side attack and the double-inversion retention pathways. The Walden-inversion SN2 channel becomes direct rebound dominated with increasing collision energy as indicated by backward scattering, initial back-side attack preference, and the redshifting of product internal energy peaks in accord with CF stretching populations. In the minor retention and induced-inversion pathways, almost the entire available energy transfers into product rotation-vibration, and retention mainly proceeds with indirect, slow double inversion following induced inversion with about 50% probability. Proton abstraction is dominated by direct stripping (evidenced by forward scattering) with CH3-side initial attack preference, providing mainly vibrationally ground state products with significant zero-point energy violation.
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Affiliation(s)
- Viktor Tajti
- 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
| | - 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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12
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Papp D, Li J, Guo H, Czakó G. Vibrational mode-specificity in the dynamics of the Cl + C 2H 6 → HCl + C 2H 5 reaction. J Chem Phys 2021; 155:114303. [PMID: 34551541 DOI: 10.1063/5.0062677] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We report a detailed dynamics study on the mode-specificity of the Cl + C2H6 → HCl + C2H5 H-abstraction reaction. We perform quasi-classical trajectory simulations using a recently developed high-level ab initio full-dimensional potential energy surface by exciting five different vibrational modes of ethane at four collision energies. We find that all the studied vibrational excitations, except that of the CC-stretching mode, clearly promote the title reaction, and the vibrational enhancements are consistent with the predictions of the Sudden Vector Projection (SVP) model, with the largest effect caused by the CH-stretching excitations. Intramolecular vibrational redistribution is also monitored for the differently excited ethane molecule. Our results indicate that the mechanism of the reaction changes with increasing collision energy, with no mode-specificity at high energies. The initial translational energy mostly converts into product recoil, while a significant part of the excess vibrational energy remains in the ethyl radical. An interesting competition between translational and vibrational energies is observed for the HCl vibrational distribution: the effect of exciting the low-frequency ethane modes, having small SVP values, is suppressed by translational excitation, whereas a part of the excess vibrational energy pumped into the CH-stretching modes (larger SVP values) efficiently flows into the HCl vibration.
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Affiliation(s)
- Dóra Papp
- 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
| | - Jun Li
- School of Chemistry and Chemical Engineering and Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, China
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - 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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13
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Czakó G, Győri T, Papp D, Tajti V, Tasi DA. First-Principles Reaction Dynamics beyond Six-Atom Systems. J Phys Chem A 2021; 125:2385-2393. [PMID: 33631071 PMCID: PMC8028310 DOI: 10.1021/acs.jpca.0c11531] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 02/05/2021] [Indexed: 11/29/2022]
Abstract
Moving beyond the six-atomic benchmark systems, we discuss the new age and future of first-principles reaction dynamics, which investigates complex, multichannel chemical reactions. We describe the methodology starting from the benchmark ab initio characterization of the stationary points, followed by full-dimensional potential energy surface (PES) developments and reaction dynamics computations. We highlight our composite ab initio approach providing benchmark stationary-point properties with subchemical accuracy, the Robosurfer program system enabling automatic PES development, and applications for the Cl + C2H6, F + C2H6, and OH- + CH3I post-six-atom reactions focusing on ab initio issues and their solutions as well as showing the excellent agreement between theory and experiment.
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Affiliation(s)
- 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
| | - 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
| | - Dóra Papp
- 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
| | - Viktor Tajti
- 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
| | - Domonkos A. Tasi
- 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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14
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Szűcs T, Czakó G. Benchmark ab initio stationary-point characterization of the complex potential energy surface of the multi-channel Cl + CH 3NH 2 reaction. Phys Chem Chem Phys 2021; 23:10347-10356. [PMID: 33881412 DOI: 10.1039/d0cp06392d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We characterize the exothermic low/submerged-barrier hydrogen-abstraction (HCl + CH2NH2/CH3NH) as well as, for the first time, the endothermic high-barrier amino-substitution (CH3Cl + NH2), methyl-substitution (NH2Cl + CH3), and hydrogen-substitution (CH2ClNH2/CH3NHCl + H) pathways of the Cl + CH3NH2 reaction using an accurate composite ab initio approach. The computations reveal a CH3NH2Cl complex in the entrance channel, nine transition states corresponding to different abstractions, Walden-inversion substitution, and configuration-retaining front-side attack substitution pathways, as well as nine post-reaction complexes. The global minima of the electronic and vibrationally adiabatic potential energy surfaces correspond to the pre-reaction CH3NH2Cl and post-reaction CH2NH2HCl complexes, respectively. The benchmark composite energies of the stationary points are obtained by considering basis-set effects up to the correlation-consistent polarized valence quadruple-zeta basis augmented with diffuse functions (aug-cc-pVQZ) using the explicitly-correlated coupled-cluster singles, doubles, and perturbative triples CCSD(T)-F12b method, post-(T) correlation up to CCSDT(Q) including full triples and perturbative quadruples, core correlation, and scalar relativistic and spin-orbit effects, as well as harmonic zero-point energy corrections.
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Affiliation(s)
- Tímea Szűcs
- 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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