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Mukherjee S, Barbatti M. A Hessian-Free Method to Prevent Zero-Point Energy Leakage in Classical Trajectories. J Chem Theory Comput 2022; 18:4109-4116. [PMID: 35679615 DOI: 10.1021/acs.jctc.2c00216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The problem associated with the zero-point energy (ZPE) leak in classical trajectory calculations is well known. Since ZPE is a manifestation of the quantum uncertainty principle, there are no restrictions on energy during the classical propagation of nuclei. This phenomenon can lead to unphysical results, such as forming products without the ZPE in the internal vibrational degrees of freedom (DOFs). The ZPE leakage also permits reactions below the quantum threshold for the reaction. We have developed a new Hessian-free method, inspired by the Lowe-Andersen thermostat model, to prevent energy dipping below a threshold in the local-pair (LP) vibrational DOFs. The idea is to pump the leaked energy to the corresponding local vibrational mode taken from the other vibrational DOFs. We have applied the new correction protocol on the ab-initio ground-state molecular dynamics simulation of the water dimer (H2O)2, which dissociates due to unphysical ZPE spilling from high-frequency OH modes. The LP-ZPE method has been able to prevent the ZPE spilling of the OH stretching modes by pumping back the leaked energy into the corresponding modes, while this energy is taken from the other modes of the dimer itself, keeping the system as a microcanonical ensemble.
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Affiliation(s)
| | - Mario Barbatti
- Aix Marseille University, CNRS, ICR, Marseille, France.,Institut Universitaire de France, 75231 Paris, France
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2
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Chavarrio Cañas JE, Monge-Palacios M, Grajales-González E, Sarathy SM. Early Chemistry of Nicotine Degradation in Heat-Not-Burn Smoking Devices and Conventional Cigarettes: Implications for Users and Second- and Third-Hand Smokers. J Phys Chem A 2021; 125:3177-3188. [PMID: 33834773 PMCID: PMC8154610 DOI: 10.1021/acs.jpca.1c01650] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nicotine exposure results in health risks not only for smokers but also for second- and third-hand smokers. Unraveling nicotine's degradation mechanism and the harmful chemicals that are produced under different conditions is vital to assess exposure risks. We performed a theoretical study to describe the early chemistry of nicotine degradation by investigating two important reactions that nicotine can undergo: hydrogen abstraction by hydroxyl radicals and unimolecular dissociation. The former contributes to the control of the degradation mechanism below 800 K due to a non-Arrhenius kinetics, which implies an enhancement of reactivity as temperature decreases. The latter becomes important at higher temperatures due to its larger activation energy. This change in the degradation mechanism is expected to affect the composition of vapors inhaled by smokers and room occupants. Conventional cigarettes, which operate at temperatures higher than 1000 K, are more prone to yield harmful pyridinyl radicals via nicotine dissociation, while nicotine in electronic cigarettes and vaporizers, with operating temperatures below 600 K, will be more likely degraded by hydroxyl radicals, resulting in a vapor with a different composition. Although low-temperature nicotine delivery devices have been claimed to be less harmful due to their nonburning operating conditions, the non-Arrhenius kinetics that we observed for the degradation mechanism below 873 K suggests that nicotine degradation may be more rapidly initiated as temperature is reduced, indicating that these devices may be more harmful than it is commonly assumed.
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Affiliation(s)
- Javier E Chavarrio Cañas
- Clean Combustion Research Center (CCRC), Physical Science and Engineering (PSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - M Monge-Palacios
- Clean Combustion Research Center (CCRC), Physical Science and Engineering (PSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - E Grajales-González
- Clean Combustion Research Center (CCRC), Physical Science and Engineering (PSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - S Mani Sarathy
- Clean Combustion Research Center (CCRC), Physical Science and Engineering (PSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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Saito K, Sugiura Y, Miyazaki T, Takahashi Y, Takayanagi T. Quantum calculations of the photoelectron spectra of the OH -·NH 3 anion: implications for OH + NH 3→ H 2O + NH 2 reaction dynamics. Phys Chem Chem Phys 2021; 23:6950-6958. [PMID: 33729225 DOI: 10.1039/d0cp06514e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We present the results of quantum dynamics calculations for analyzing the experimentally measured photoelectron spectra of the OH-·NH3 anion complex. Detachment of an excess electron of OH-·NH3 initially produces a molecular arrangement, which is close to the transition-state structure of the neutral OH + NH3→ H2O + NH2 hydrogen abstraction reaction due to the Franck-Condon principle, and thus finally leads to the OH + NH3 or H2O + NH2 asymptotic channel. We used both the path integral method and the reduced-dimensionality quantum wave packet method to simulate the photoelectron spectra of the OH-·NH3 anion. The calculated spectra were found to be in qualitative agreement with the experimental spectra. It was found that the photodetached complex mainly dissociates into the OH + NH3 channel; however, we found that the hydrogen exchange process also contributes to the photodetachment spectra.
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Affiliation(s)
- Kohei Saito
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
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Quasi-Classical Trajectory Study of the CN + NH 3 Reaction Based on a Global Potential Energy Surface. Molecules 2021; 26:molecules26040994. [PMID: 33668582 PMCID: PMC7918900 DOI: 10.3390/molecules26040994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/10/2021] [Accepted: 02/11/2021] [Indexed: 11/17/2022] Open
Abstract
Based on a combination of valence-bond and molecular mechanics functions which were fitted to high-level ab initio calculations, we constructed an analytical full-dimensional potential energy surface, named PES-2020, for the hydrogen abstraction title reaction for the first time. This surface is symmetrical with respect to the permutation of the three hydrogens in ammonia, it presents numerical gradients and it improves the description presented by previous theoretical studies. In order to analyze its quality and accuracy, stringent tests were performed, exhaustive kinetics and dynamics studies were carried out using quasi-classical trajectory calculations, and the results were compared with the available experimental evidence. Firstly, the properties (geometry, vibrational frequency and energy) of all stationary points were found to reasonably reproduce the ab initio information used as input; due to the complicated topology with deep wells in the entrance and exit channels and a “submerged” transition state, the description of the intermediate complexes was poorer, although it was adequate to reasonably simulate the kinetics and dynamics of the title reaction. Secondly, in the kinetics study, the rate constants simulated the experimental data in the wide temperature range of 25–700 K, improving the description presented by previous theoretical studies. In addition, while previous studies failed in the description of the kinetic isotope effects, our results reproduced the experimental information. Finally, in the dynamics study, we analyzed the role of the vibrational and rotational excitation of the CN(v,j) reactant and product angular scattering distribution. We found that vibrational excitation by one quantum slightly increased reactivity, thus reproducing the only experimental measurement, while rotational excitation strongly decreased reactivity. The scattering distribution presented a forward-backward shape, associated with the presence of deep wells along the reaction path. These last two findings await experimental confirmation.
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Espinosa-Garcia J, García-Chamorro M, Corchado JC. Rethinking the description of water product in polyatomic OH/OD + XH (X ≡ D, Br, NH2 and GeH3) reactions: theory/experimental comparison. Theor Chem Acc 2020. [DOI: 10.1007/s00214-020-2577-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Nguyen TL, Stanton JF. High-level theoretical study of the reaction between hydroxyl and ammonia: Accurate rate constants from 200 to 2500 K. J Chem Phys 2018; 147:152704. [PMID: 29055339 DOI: 10.1063/1.4986151] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hydrogen abstraction from NH3 by OH to produce H2O and NH2-an important reaction in combustion of NH3 fuel-was studied with a theoretical approach that combines high level quantum chemistry and advanced chemical kinetics methods. Thermal rate constants calculated from first principles agree well (within 5%-20%) with available experimental data over a temperature range that extends from 200 to 2500 K. Quantum mechanical tunneling effects were found to be important; they lead to a decided curvature and non-Arrhenius behavior for the rate constant.
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Affiliation(s)
- Thanh Lam Nguyen
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - John F Stanton
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
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Vibrational distribution and dynamics study of the HCN(v
1, v
2, v
3) product in the CN + CH4 hydrogen abstraction reaction. Theor Chem Acc 2017. [DOI: 10.1007/s00214-017-2155-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Bera PP, Stein T, Head-Gordon M, Lee TJ. Mechanisms of the Formation of Adenine, Guanine, and Their Analogues in UV-Irradiated Mixed NH 3:H 2O Molecular Ices Containing Purine. ASTROBIOLOGY 2017; 17:771-785. [PMID: 28708419 PMCID: PMC5734622 DOI: 10.1089/ast.2016.1614] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We investigated the formation mechanisms of the nucleobases adenine and guanine and the nucleobase analogues hypoxanthine, xanthine, isoguanine, and 2,6-diaminopurine in a UV-irradiated mixed 10:1 H2O:NH3 ice seeded with precursor purine by using ab initio and density functional theory computations. Our quantum chemical investigations suggest that a multistep reaction mechanism involving purine cation, hydroxyl and amino radicals, together with water and ammonia, explains the experimentally obtained products in an independent study. The relative abundances of these products appear to largely follow from relative thermodynamic stabilities. The key role of the purine cation is likely to be the reason why purine is not functionalized in pure ammonia ice, where cations are promptly neutralized by free electrons from NH3 ionization. Amine group addition to purine is slightly favored over hydroxyl group attachment based on energetics, but hydroxyl is much more abundant due to higher abundance of H2O. The amino group is preferentially attached to the 6 position, giving 6-aminopurine, that is, adenine, while the hydroxyl group is preferentially attached to the 2 position, leading to 2-hydroxypurine. A second substitution by hydroxyl or amino group occurs at either the 6 or the 2 position depending on the first substitution. Given that H2O is far more abundant than NH3 in the experimentally studied ices (as well as based on interstellar abundances), xanthine and isoguanine are expected to be the most abundant bi-substituted photoproducts. Key Words: Astrophysical ice-Abiotic organic synthesis-Nucleic acids-Origin of life-RNA world. Astrobiology 17, 771-785.
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Affiliation(s)
- Partha P. Bera
- NASA Ames Research Center, Moffett Field, Mountain View, CA, USA
- Bay Area Environmental Research Institute, Petaluma, CA, USA
| | - Tamar Stein
- University of California, Berkeley, CA, USA
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Martin Head-Gordon
- University of California, Berkeley, CA, USA
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Timothy J. Lee
- NASA Ames Research Center, Moffett Field, Mountain View, CA, USA
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Espinosa-Garcia J, Corchado JC. QCT dynamics study of OH/OD + GeH4 reactions. The problem of water bending excitation. Phys Chem Chem Phys 2017; 19:1580-1589. [DOI: 10.1039/c6cp08118e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The difficulties in the description of the water bending population could be related to the zero-point violation problem in QCT calculations.
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Affiliation(s)
- J. Espinosa-Garcia
- Departamento de Quimica Fisica and Instituto de Computación Científica Avanzada (ICCAEx)
- Universidad de Extremadura
- 06071 Badajoz
- Spain
| | - J. C. Corchado
- Departamento de Quimica Fisica and Instituto de Computación Científica Avanzada (ICCAEx)
- Universidad de Extremadura
- 06071 Badajoz
- Spain
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Butkovskaya NI, Setser DW. Branching Ratios and Vibrational Distributions in Water-Forming Reactions of OH and OD Radicals with Methylamines. J Phys Chem A 2016; 120:6698-711. [PMID: 27504785 DOI: 10.1021/acs.jpca.6b06411] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reactions of OH and OD radicals with (CH3)3N, (CH3)2NH, and CH3NH2 were studied by Fourier transform infrared emission spectroscopy (FTIR) of the water product molecules from a fast-flow reactor at 298 K. The rate constants (4.4 ± 0.5) × 10(-11), (5.2 ± 0.8) × 10(-11), and (2.0 ± 0.4) × 10(-11) cm(3) molecule(-1) s(-1) were determined for OD + (CH3)3N, (CH3)2NH, and CH3NH2, respectively, by comparing the HOD emission intensities to the HOD intensity from the OD reaction with H2S. Abstraction from the nitrogen site competes with abstraction from the methyl group, as obtained from an analysis of the HOD and D2O emission intensities from the OD reactions with the deuterated reactants, (CD3)2NH and CD3NH2. After adjustment for the hydrogen-deuterium kinetic isotope effect, the product branching fractions of the hydrogen abstraction from the nitrogen for di- and monomethylamine were found to be 0.34 ± 0.04 and 0.26 ± 0.05, respectively. Vibrational distributions of the H2O, HOD, and D2O molecules are typical for direct hydrogen atom abstraction from polar molecules, even though activation energies are negative because of the formation of pre-transition-state complexes. Comparison is made to the reactions of hydroxyl radicals with ammonia and with other compounds with primary C-H bonds to discuss specific features of disposal of energy to water product.
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Affiliation(s)
- N I Butkovskaya
- Semenov Institute of Chemical Physics, Russian Academy of Sciences , 119991 Moscow, Russian Federation
| | - D W Setser
- Department of Chemistry, Kansas State University , Manhattan, Kansas 66506, United States
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Long B, Tan XF, Wang YB, Li J, Ren DS, Zhang WJ. Theoretical Studies on Reactions of OH with H2SO4…NH3Complex and NH2with H2SO4in the Presence of Water. ChemistrySelect 2016. [DOI: 10.1002/slct.201600194] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Bo Long
- College of Information Engineering; Guizhou Minzu University; Guiyang 550025 China
| | - Xing-Feng Tan
- College of Information Engineering; Guizhou Minzu University; Guiyang 550025 China
| | - Yi-Bo Wang
- Key Laboratory of Guizhou High Performance Computational Chemistry; Department of Chemistry; Guizhou University; Guiyang 550025 China
| | - Jun Li
- Department of Chemistry & Laboratory of Organic; Optoelectronics and Molecular Engineering of the Ministry of Education; Tsinghua University; Beijing 100084 China
| | - Da-Sen Ren
- College of Information Engineering; Guizhou Minzu University; Guiyang 550025 China
| | - Wei-Jun Zhang
- Laboratory of Atmospheric Physico-Chemistry; Anhui Institute of Optics and Fine Mechanics; Chinese Academy of Sciences; Hefei 230031 China
- Key Laboratory of Atmospheric Composition and Optical Radiation; Anhui Institute of Optics and Fine Mechanics; Chinese Academy of Sciences; Hefei 230031 China
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Espinosa-Garcia J, Corchado JC. QCT dynamics study of the reaction of hydroxyl radical and methane using a new ab initio fitted full-dimensional analytical potential energy surface. Theor Chem Acc 2015. [DOI: 10.1007/s00214-014-1607-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Espinosa-Garcia J, Corchado J, Bonnet L. Quasi-classical trajectory study of the water vibrational distribution for the polyatomic OH/OD+NH3 reactions: Comparison with experiment. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2014.12.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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14
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Monge-Palacios M, Espinosa-Garcia J. Bond and mode selectivity in the OH + NH2D reaction: a quasi-classical trajectory calculation. Phys Chem Chem Phys 2013; 15:19180-90. [DOI: 10.1039/c3cp52809j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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