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Chalkopiadis L, Lambropoulos K, Simserides C. Electronic structure, absorption spectra and oxidation dynamics in polyynes and dicyanopolyynes. Phys Chem Chem Phys 2024; 26:22149-22163. [PMID: 39119726 DOI: 10.1039/d4cp02719a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2024]
Abstract
The advent of femtosecond to attosecond experimental tools has made now possible to study such ultrafast carrier dynamics, e.g., the spatial and temporal charge density evolution, after an initial oxidation or reduction in molecules, candidates for atomic wires like polyynes and dicyanopolyynes. Here, we study the electronic structure and hole transfer in symmetric molecules containing carbon, nitrogen and hydrogen, the first members in the series of polyynic carbynes and dicyanopolyynes, using methods based on density functional theory (DFT): constrained DFT (CDFT), time-dependent DFT (TDDFT) and real-time TDDFT (RT-TDDFT), with Löwdin population analysis, comparing many levels of theory and obtaining convergence of the results. For the same purposes, we develop a tight binding (TB) variant using all valence orbitals of all atoms. This TB variant is applied here in linear molecules, but it is also adequate for electronic structure, charge transfer and charge transport of non-linear molecules and clusters of molecules. We calculate the electronic structure, the time-dependent dipole moment and the probabilities of finding the hole at each site, their mean over time values, the mean transfer rates from the oxidation site to other sites and the frequency content (using charge as well as dipole moment oscillations). We take into account zero-point motion. The initial conditions for RT-TDDFT are obtained by CDFT. For TB, we explore different initial conditions: we place the hole at a particular orbital or distribute it among a number of orbitals; it is also possible to include phase differences between orbitals. Finally, we compare with available experimental data.
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Affiliation(s)
- Lazaros Chalkopiadis
- Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos GR-15784, Athens, Greece.
| | - Konstantinos Lambropoulos
- Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos GR-15784, Athens, Greece.
| | - Constantinos Simserides
- Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos GR-15784, Athens, Greece.
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Kushwaha A, Chahal P, Dhilip Kumar TJ. Rotational dynamics of CNCN by p-H2 and o-H2 collision at interstellar temperatures. J Chem Phys 2024; 161:064302. [PMID: 39120031 DOI: 10.1063/5.0220608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2024] [Accepted: 07/23/2024] [Indexed: 08/10/2024] Open
Abstract
The rotational dynamics of isocyanogen (CNCN) is studied for its collision with para (p-) and ortho (o-) hydrogen (H2) in the temperature range of 1-100 K. These temperatures correspond to the cold dense molecular clouds in the interstellar medium where molecular hydrogen is the primary collider. An ab initio 4D potential energy surface (PES) is constructed keeping the two molecules under rigid rotor approximation. The PES is generated using the CCSD(T)-F12b/AVTZ level of theory. The 4D PES is further fitted into a neural network (NN) model, which can augment the surface and account for missing data points within spectroscopic accuracy. This NN-fitted PES is then expanded over a bispherical harmonics function to get radial terms, which are expressed into analytic functions. Thereafter, the cross sections (σ) are computed for rotational transitions of CNCN (j → j') using the close-coupling and centrifugal sudden methods for both p-H2 (jc = 0) and o-H2 (jc = 1) collision till 194 cm-1. In addition, p-H2 (jc = 0, 2) cross sections are also computed using the centrifugal sudden approximation method. The collisional rates are achieved by taking the Boltzmann distribution of σ over the translational energy of H2 till 100 K. Finally, the CNCN-H2 rates are compared to CNCN-He and NCCN-H2 collisional rates. Comparing even and odd transitions for the CNCN-H2 rates show a propensity toward higher rates for even transitions especially for o-H2 collisions considering low-order transitions.
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Affiliation(s)
- Apoorv Kushwaha
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, India
| | - Pooja Chahal
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, India
| | - T J Dhilip Kumar
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, India
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3
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Nixon CA. The Composition and Chemistry of Titan's Atmosphere. ACS EARTH & SPACE CHEMISTRY 2024; 8:406-456. [PMID: 38533193 PMCID: PMC10961852 DOI: 10.1021/acsearthspacechem.2c00041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 11/02/2023] [Accepted: 02/02/2024] [Indexed: 03/28/2024]
Abstract
In this review I summarize the current state of knowledge about the composition of Titan's atmosphere and our current understanding of the suggested chemistry that leads to that observed composition. I begin with our present knowledge of the atmospheric composition, garnered from a variety of measurements including Cassini-Huygens, the Atacama Large Millimeter/submillimeter Array, and other ground- and space-based telescopes. This review focuses on the typical vertical profiles of gases at low latitudes rather than global and temporal variations. The main body of the review presents a chemical description of how complex molecules are believed to arise from simpler species, considering all known "stable" molecules-those that have been uniquely identified in the neutral atmosphere. The last section of the review is devoted to the gaps in our present knowledge of Titan's chemical composition and how further work may fill those gaps.
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Affiliation(s)
- Conor A. Nixon
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland 20771, United
States
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Ritika, Dhilip Kumar TJ. New potential energy surface and rotational deexcitation cross-sections of CNNC by para-H 2 ( jp = 0). Phys Chem Chem Phys 2023; 25:24904-24911. [PMID: 37681247 DOI: 10.1039/d3cp03354f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
The objective of this study is to enhance our understanding of the existence of molecules in interstellar space by determining the collisional rate coefficients with the most prevalent species. The study examines the impact of para-H2 collisions, specifically when it is in its ground vibrational state with a nuclear spin of para-H2, i.e., jp = 0, on causing the rotational deexcitation of the diisocyanogen (CNNC) molecule. These scattering data are obtained as a result of spherically averaging a four-dimensional potential energy surface (4DPES) over the H2 orientations. Using the CCSD(T)-F12a approach and aug-cc-pVTZ basis sets, the ab initio 4DPES for the CNNC-H2 van der Waals system is calculated. The CNNC-para-H2 4DPES attains a global minimum of 221.38 cm-1 at the CNNC and H2 center of mass distance (R) of 3.1 Å. The method of close coupling calculations is employed for the purpose of calculating the cross-sectional data of CNNC with para-H2 (jp = 0), for total energies up to 1000 cm-1. Rate coefficients are computed over the temperature range of 1 K to 100 K. Propensity suggests that even Δj transitions are strongly preferred. The rate coefficients for CNNC-H2 are determined to be 0.90-2.95 times those of CNNC-He, which implies it is not reliable to estimate the H2 rate coefficients by multiplying the rate coefficients for CNNC-He collision with a scaling factor of 1.38.
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Affiliation(s)
- Ritika
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology, Ropar, Rupnagar 140001, India.
| | - T J Dhilip Kumar
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology, Ropar, Rupnagar 140001, India.
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Cao S, Yuan W, Li Y, Teng X, Si H, Chen R, Zhu Y. Photoredox/copper cocatalyzed domino cyclization of oxime esters with TMSCN: access to antifungal active tetrasubstituted pyrazines. Chem Commun (Camb) 2022; 58:7200-7203. [PMID: 35671164 DOI: 10.1039/d2cc02480b] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A photoredox/copper cocatalyzed domino cyclization of oxime esters with TMSCN has been developed. A range of structurally novel tetrasubstituted pyrazines have been obtained. This method features high bond-forming efficiency, high step economy, broad substrate scope, and gram-scale synthesis. Moreover, preliminary bioactivity evaluation of pyrazine products shows their promising antifungal activities.
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Affiliation(s)
- Shujun Cao
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
| | - Weidong Yuan
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
| | - Yun Li
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
| | - Xinjie Teng
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
| | - Huaxing Si
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
| | - Rongshun Chen
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
| | - Yingguang Zhu
- Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
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Semiempirical Potential in Kinetics Calculations on the HC3N + CN Reaction. Molecules 2022; 27:molecules27072297. [PMID: 35408696 PMCID: PMC9000235 DOI: 10.3390/molecules27072297] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/25/2022] [Accepted: 03/28/2022] [Indexed: 02/04/2023] Open
Abstract
The reaction between the cyano radical CN and cyanoacetylene molecule HC3N is of great interest in different astronomical fields, from star-forming regions to planetary atmospheres. In this work, we present a new synergistic theoretical approach for the derivation of the rate coefficient for gas phase neutral-neutral reactions. Statistic RRKM calculations on the Potential Energy Surface are coupled with a semiempirical analysis of the initial bimolecular interaction. The value of the rate coefficient for the HC3N + CN → H + NCCCCN reaction obtained with this method is compared with previous theoretical and experimental investigations, showing strengths and weaknesses of the new presented approach.
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Ritika, Chhabra S, Dhilip Kumar TJ. Electronic structure calculations and quantum dynamics of rotational deexcitation of CNNC by He. Phys Chem Chem Phys 2022; 24:2785-2793. [PMID: 35039815 DOI: 10.1039/d1cp04273d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The quantum dynamics of rotational transitions of the diisocyanogen (CNNC) molecule undergoing collision with the helium (He) atom occurring in the interstellar medium (ISM) has been studied. The rotational deexcitation cross sections are extracted by first computing an ab initio potential energy surface of CNNC-He using the coupled-cluster with single and double and perturbative triple excitations with the F12a method (CCSD(T)-F12a) employing the aug-cc-pVTZ basis set. Utilizing the multipole expansions, collisional cross sections are determined for total energies of up to 1000 cm-1 by the close coupling equations. The discussion on propensity rules suggests that the transitions have even Δj values, while odd Δj valued transitions are forbidden due to C and N nuclei spin statistics. Quasi-bound states present in the CNNC-He van der Waals complex resulted in the resonances coming from the rapid oscillations in the values of the cross sections in the region of low energy. Rotational deexcitation rate coefficients are further worked out by averaging the calculated cross sections at temperatures below 200 K. The new findings of the study will be beneficial in modeling the abundance of diisocyanogen in the ISM.
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Affiliation(s)
- Ritika
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology, Ropar, Rupnagar 140001, India.
| | - Sanchit Chhabra
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology, Ropar, Rupnagar 140001, India.
| | - T J Dhilip Kumar
- Quantum Dynamics Lab, Department of Chemistry, Indian Institute of Technology, Ropar, Rupnagar 140001, India.
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9
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Chhabra S, Kushwaha A, Kaur R, Dhilip Kumar T. Ultracold rotational quenching of NCCN scattering with 3He and 4He. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2019.136819] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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10
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Nuñez-Reyes D, Loison JC, Hickson KM, Dobrijevic M. Rate constants for the N(2D) + C2H2 reaction over the 50–296 K temperature range. Phys Chem Chem Phys 2019; 21:22230-22237. [DOI: 10.1039/c9cp04170b] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reactions of metastable atomic nitrogen N(2D) are important processes in the gas-phase chemistry of several planetary atmospheres.
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Affiliation(s)
- Dianailys Nuñez-Reyes
- Université de Bordeaux
- Institut des Sciences Moléculaires
- UMR 5255
- F-33400 Talence
- France
| | | | - Kevin M. Hickson
- Université de Bordeaux
- Institut des Sciences Moléculaires
- UMR 5255
- F-33400 Talence
- France
| | - Michel Dobrijevic
- Laboratoire d'Astrophysique de Bordeaux
- Université de Bordeaux
- CNRS
- F-33615 Pessac
- France
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11
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Chhabra S, Kushwaha A, Dhilip Kumar TJ. Quantum dynamics study of rotational transitions of NCCN induced by He collision. J Chem Phys 2018; 149:174312. [PMID: 30408997 DOI: 10.1063/1.5058126] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Quantum dynamics of the molecule cyanogen (NCCN) and its collision with helium taking place in the interstellar medium has been studied. An ab initio potential energy surface of NCCN-He, a van der Waals complex, is generated using the high-level single reference coupled-cluster with single and double and perturbative triple excitation method and aug-cc-pVQZ basis sets. Using the multipole expansion, Legendre coefficients have been calculated and utilized in determining collisional cross sections. Close-coupling calculations have been performed to study rotational excitations for He collision with NCCN. Due to nuclear spin statistics, collision induced transitions have even Δj, while odd Δj transitions are forbidden. The presence of resonances arising from rapid oscillation of cross sections in the low energy region is the result of quasi-bound states in the NCCN-He van der Waals complex. Among all the transitions, Δj = 2 are found to be predominant for excitation. Thereafter, for each transition, the rate coefficients have been calculated which decrease with increasing values of j and Δj. The result of this work will be helpful to accurately model the abundance of cyanogen in stellar atmospheres and interstellar gas.
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Affiliation(s)
- Sanchit Chhabra
- Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, India
| | - Apoorv Kushwaha
- Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, India
| | - T J Dhilip Kumar
- Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, India
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12
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Agúndez M, Marcelino N, Cernicharo J. Discovery of Interstellar Isocyanogen (CNCN): Further Evidence that Dicyanopolyynes are Abundant in Space. THE ASTROPHYSICAL JOURNAL. LETTERS 2018; 861:L22. [PMID: 30186588 PMCID: PMC6120679 DOI: 10.3847/2041-8213/aad089] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
It is thought that dicyanopolyynes could be potentially abundant interstellar molecules, although their lack of dipole moment makes it impossible to detect them through radioastronomical techniques. Recently, the simplest member of this chemical family, cyanogen (NCCN), was indirectly probed for the first time in interstellar space through the detection of its protonated form toward the dense clouds L483 and TMC-1. Here we present a second firm evidence of the presence of NCCN in interstellar space, namely the detection of the metastable and polar isomer isocyanogen (CNCN). This species has been identified in L483 and tentatively in TMC-1 by observing various rotational transitions in the λ 3 mm band with the IRAM 30m telescope. We derive beam-averaged column densities for CNCN of 1.6 × 1012 cm-2 in L483 and 9 × 1011 cm-2 in TMC-1, which imply fractional abundances relative to H2 in the range (5 - 9) × 10-11. While the presence of NCCN in interstellar clouds seems out of doubt owing to the detection of NCCNH+ and CNCN, putting tight constraints on its abundance is still hampered by the poor knowledge of the chemistry that links NCCN with NCCNH+ and especially with CNCN. We estimate that NCCN could be fairly abundant, in the range 10-9-10-7 relative to H2, as other abundant nitriles like HCN and HC3N.
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Affiliation(s)
- M Agúndez
- Instituto de Física Fundamental, CSIC, C/ Serrano 123, 28006 Madrid, Spain
| | - N Marcelino
- Instituto de Física Fundamental, CSIC, C/ Serrano 123, 28006 Madrid, Spain
| | - J Cernicharo
- Instituto de Física Fundamental, CSIC, C/ Serrano 123, 28006 Madrid, Spain
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13
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Faßheber N, Lamoureux N, Friedrichs G. The rate constant of the reaction NCN + H2 and its role in NCN and NO modeling in low pressure CH4/O2/N2-flames. Phys Chem Chem Phys 2015; 17:15876-86. [DOI: 10.1039/c5cp01414j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The high temperature rate constant of the so-far neglected reaction NCN + H2 has been measured for the first time and its influence on NOx flame modeling has been evaluated by implementation into the GDFkin3.0_NCN mechanism.
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Affiliation(s)
- Nancy Faßheber
- Institut für Physikalische Chemie
- Christian-Albrechts-Universität zu Kiel
- 24118 Kiel
- Germany
| | - Nathalie Lamoureux
- Laboratoire PC2A
- UMR8522 CNRS/Université Lille 1
- 59655 Villeneuve d'Ascq
- France
| | - Gernot Friedrichs
- Institut für Physikalische Chemie
- Christian-Albrechts-Universität zu Kiel
- 24118 Kiel
- Germany
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Leach S, Schwell M, Garcia GA, Bénilan Y, Fray N, Gazeau MC, Gaie-Levrel F, Champion N, Guillemin JC. Ionization photophysics and spectroscopy of dicyanoacetylene. J Chem Phys 2013; 139:184304. [PMID: 24320271 DOI: 10.1063/1.4826467] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photoionization of dicyanoacetylene was studied using synchrotron radiation over the excitation range 8-25 eV, with photoelectron-photoion coincidence techniques. The absolute ionization cross-section and detailed spectroscopic aspects of the parent ion were recorded. The adiabatic ionization energy of dicyanoacetylene was measured as 11.80 ± 0.01 eV. A detailed analysis of the cation spectroscopy involves new aspects and new assignments of the vibrational components to excitation of the quasi-degenerate A(2)Πg, B(2)Σg(+) states as well as the C(2)Σu(+) and D(2)Πu states of the cation. Some of the structured autoionization features observed in the 12.4-15 eV region of the total ion yield spectrum were assigned to vibrational components of valence shell transitions and to two previously unknown Rydberg series converging to the D(2)Πu state of C4N2(+). The appearance energies of the fragment ions C4N(+), C3N(+), C4(+), C2N(+), and C2(+) were measured and their heats of formation were determined and compared with existing literature values. Thermochemical calculations of the appearance potentials of these and other weaker ions were used to infer aspects of dissociative ionization pathways.
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Affiliation(s)
- Sydney Leach
- LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon, France
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15
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Cheikh Sid Ely S, Morales SB, Guillemin JC, Klippenstein SJ, Sims IR. Low Temperature Rate Coefficients for the Reaction CN + HC3N. J Phys Chem A 2013; 117:12155-64. [DOI: 10.1021/jp406842q] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sidaty Cheikh Sid Ely
- Institut
de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042 Rennes Cedex, France
| | - Sébastien B. Morales
- Institut
de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042 Rennes Cedex, France
| | - Jean-Claude Guillemin
- Ecole
Nationale Supérieure de Chimie de Rennes, CNRS UMR 6226, 11 Allée
de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France
| | - Stephen J. Klippenstein
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Ian R. Sims
- Institut
de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042 Rennes Cedex, France
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16
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Mal’kina AG, Shemyakina OA, Nosyreva VV, Albanov AI, Klyba LV, Zhanchipova ER, Trofimov BA. Transformations of cyanoacetylenic alcohols in the presence of the cyanide ion. MENDELEEV COMMUNICATIONS 2006. [DOI: 10.1070/mc2006v016n04abeh002250] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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17
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Maeda S, Ohno K. Global Mapping of Equilibrium and Transition Structures on Potential Energy Surfaces by the Scaled Hypersphere Search Method: Applications to ab Initio Surfaces of Formaldehyde and Propyne Molecules. J Phys Chem A 2005; 109:5742-53. [PMID: 16833907 DOI: 10.1021/jp0513162] [Citation(s) in RCA: 263] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Technical details of a new global mapping technique for finding equilibrium (EQ) and transition structures (TS) on potential energy surfaces (PES), the scaled hypersphere search (SHS) method (Ohno, K.; Maeda, S. Chem. Phys. Lett. 2004, 384, 277), are presented. On the basis of a simple principle that reaction pathways are found as anharmonic downward distortions of PES around an EQ point, the reaction pathways can be obtained as energy minima on the scaled hypersphere surface, which would have a constant energy when the potentials are harmonic. Connections of SHS paths between each EQ are very similar to corresponding intrinsic reaction coordinate (IRC) connections. The energy maximum along the SHS path reaches a region in close proximity to the TS of the reaction pathway, and the subsequent geometry optimization from the SHS maximum structure easily converges to the TS. The SHS method, using the one-after-another algorithm connecting EQ and TS, considerably reduces the multidimensional space to be searched to certain limited regions around the pathways connecting each EQ with the neighboring TS. Applications of the SHS method have been made to ab initio surfaces of formaldehyde and propyne molecules to obtain systematically five EQ and nine TS for formaldehyde and seven EQ and 32 TS for propyne.
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Affiliation(s)
- Satoshi Maeda
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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Osamura Y, Petrie S. NCCN and NCCCCN Formation in Titan's Atmosphere: 1. Competing Reactions of Precursor HCCN (3A‘ ‘) with H (2S) and CH3(2A‘). J Phys Chem A 2004. [DOI: 10.1021/jp037817+] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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