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Full dimensional ab-initio dynamics calculations of electron capture processes by the H₃O⁺ ion

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 2000年第19期2卷 4327-4333页

作者： Tachikawa, H Hokkaido Univ Grad Sch Engn Div Mol Chem Sapporo Hokkaido 0608628 Japan

dynamics of H3O following the electron capture by H3O+, which plays an important role in the H2O formation in interstellar cloud, have been investigated by means of ab-initio direct dynamics calculations. The full dimensional potential energy surface, calculated at the HF/6-311+G(d,p) level, was used in the dynamics calculation throughout. The reaction proceeds on the ground state of H3O with zero excess energy at time zero, while H3O is formed by vertical electron capture by H3O+ without structural change. A total of 200 trajectories were run from an initial geometrical configuration generated by ab-initio molecular dynamics calculation for H3O+ at 300 K. The dynamics calculations for H3O showed that two reaction channels are involved in the decay processes of H3O, formed by electron capture by H3O+: one is a dissociation channel in which the reaction proceeds via a short-lived complex, H3O* (channel 1), and the other channel is one of complex formation in which the reaction proceeds via a long-lived complex, H3O* (channel 2). The lifetimes of the complexes for channels 1 and 2 are calculated to be about 5-60 fs and > 200 fs, respectively, although the branching ratio for channel 2 is negligibly small. The relative translational energy between H2O and H is distributed in the range 150-200 kJ mol(-1) with an average of 185 kJ mol(-1), which is 90% of the total available energy. The mechanism of the reaction has been discussed on the basis of the theoretical results.

关键词： .reaction proceeds ab-initio Long-lived excess energy electron capture translational energy dynamics calculations full dimensional time zero

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A new algorithm for efficient direct dynamics calculations of large-curvature tunneling and its application to radical reactions with 9-15 atoms

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JOURNAL OF CHEMICAL THEORY AND COMPUTATION 2005年第6期1卷 1063-1078页

作者： Fernández-Ramos, A Truhlar, DG Univ Minnesota Dept Chem Minneapolis MN 55455 USA Univ Minnesota Inst Supercomp Minneapolis MN 55455 USA Univ Santiago de Compostela Fac Quim Dept Quim Fis Santiago De Compostela 15782 Spain

We present a new algorithm for carrying out large-curvature tunneling calculations that account for extreme corner-cutting tunneling in hydrogen atom, proton, and hydride transfer reactions. The algorithm is based on two-dimensional interpolation in a physically motived set of variables that span the space of tunneling paths and tunneling energies. With this new algorithm, we are able to carry out density functional theory direct dynamics calculations of the rate constants, including multidimensional tunneling, for a set of hydrogen atom transfer reactions involving 9-15 atoms and up to 7 nonhydrogenic atoms. The reactions considered involve the abstraction of a hydrogen atom from hydrocarbons by a trifluoromethyl radical, and in particular, we consider the reactions of CF3 with CH4, C2H6, and C3H8. We also calculate several kinetic isotope effects. The electronic structure is treated by the MPWB1K/6-31+G(d,p) method, which is validated by comparison to experimental results and to CBS-Q, MCG3, and G3SX(MP3) calculations for CF3 + CH4. Harmonic vibrational frequencies along the reaction path are calculated in curvilinear coordinates with scaled frequencies, and anharmonicity is included in the lowest-frequency torsion.

关键词： .abstraction hydrogen atom paths calculate new algorithm coordinates MPWB Efficient Direct dynamics calculations Fernandez-Ramos Chem Theory Comput corner-cutting transfer reactions tunneling energies multidimensional tunneling CF CH

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Highly accurate potential-energy and dipole moment surfaces for vibrational state calculations of methane - art. no. 064311

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JOURNAL OF CHEMICAL PHYSICS 2006年第6期124卷 64311-1-64311-页

作者： Oyanagi, C Yagi, K Taketsugu, T Hirao, K Ochanomizu Univ Dept Chem Bunkyo Ku Tokyo 1128610 Japan Univ Tokyo Sch Engn Dept Appl Chem Tokyo 1138656 Japan Hokkaido Univ Grad Sch Sci Div Chem Sapporo Hokkaido 0600810 Japan

Full-dimensional ab initio potential-energy surface (PES) and dipole moment surface are constructed for a methane molecule at the CCSD(T)/cc-pVTZ and MP2/cc-pVTZ levels of theory, respectively, by the modified Shepard interpolation method based on the fourth-order Taylor expansion [MSI(4th)]. The reference points for the interpolation have been set in the coupling region of CH symmetric and antisymmetric stretching modes so as to reproduce the vibrational energy levels related to CH stretching vibrations. The vibrational configuration-interaction calculations have been performed to obtain the energy levels and the absorption intensities up to 9000 cm(-1) with the use of MSI(4th)-PES. The calculated fundamental frequencies and low-lying vibrational energy levels show that MSI(4th) is superior to the widely employed quartic force field, giving a better agreement with the experimental values. The absorption bands of overtones as well as combination bands, which are caused by purely anharmonic effects, have been obtained up to 9000 cm(-1). Strongly coupled states with visible intensity have been found in the 6500-9000 cm(-1) region where the experimental data are still lacking.

关键词： SELF-CONSISTENT-FIELD QUARTIC FORCE-FIELD CLASSICAL TRAJECTORYcalculations DOUBLE-RESONANCE OBSERVATION PERTURBATION-THEORY VARIATIONAL calculations ROVIBRATIONAL ENERGIES dynamics calculations ANHARMONIC COUPLINGS POLYATOMIC-MOLECULES

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Theoretical investigation of vibrational relaxation of NO(²Π), O₂(³Σ^-_g), and N₂(¹Σ⁺_g)in collisions with O(³P)

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MOLECULAR PHYSICS 2007年第9期105卷 1183-1191页

作者： Ivanov, M. V. Schinke, R. Mcbane, G. C. Max Planck Inst Dynam & Selbstorg D-37073 Gottingen Germany Grand Valley State Univ Dept Chem Allendale MI 49401 USA

The vibrational relaxation of NO((2)Pi), O-2((3)Sigma(-)(g)), and ((1)Sigma(+)(g)) in collisions with O(P-3) is investigated by means of classical trajectories (NO, O-2) and quantum mechanical (N-2) scattering calculations N-2 using calculated potential energy surfaces. For NO and O-2, intermediate collision complexes are formed and the relaxation rate coefficients are large, of the order of 5 x 10(-11) cm(3) s(-1) and 2 x 10(-12) cm(3) s(-1), respectively, at room temperature. The agreement with available experimental data for NO is very good. The calculated rate coefficient for O-2, however, is about two times smaller than the measured rate coefficient. In both cases, the relaxation rate coefficient is slightly smaller than the complex formation or twice the atom exchange rate. Oxygen atoms colliding with N-2, on the other hand, do not form a collision complex;the potential energy surfaces for N-2((1)Sigma(+)(g)) + O(P-3) are purely repulsive. The calculated room temperature rate coefficient is on the order of 1 x 10(-15) cm(3) s(-1);it underestimates the measured rate coefficient by about a factor of 4.

关键词： POTENTIAL-ENERGY SURFACE ATOMIC OXYGEN dynamics calculations RATECONSTANTS DISSOCIATION THRESHOLD ELECTRONIC-STRUCTURE EXCHANGE-REACTION QUANTUM dynamics REACTIVE ATOMS OZONE

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Interpolating moving least-squares methods for fitting potential energy surfaces: Analysis of an application to a six-dimensional system

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JOURNAL OF CHEMICAL PHYSICS 2004年第21期121卷 10329-10338页

作者： Maisuradze, GG Kawano, A Thompson, DL Wagner, AF Minkoff, M Oklahoma State Univ Dept Chem Stillwater OK 74078 USA Argonne Natl Lab Div Chem Argonne IL 60439 USA Argonne Natl Lab Div Math & Comp Sci Argonne IL 60439 USA

The basic formal and numerical aspects of different degree interpolated moving least-squares (IMLS) methods are applied to a six-dimensional potential energy surface (PES) of the HOOH molecule, for which an analytic ("exact") potential is available in the literature. The results of systematic investigations of the effects of weight function parameters, the degree and partial degree of IMLS, the number of data points allowed, and the optimal automatic point selection of data points up to full third-degree IMLS fits are reported. With partial reduction of cross terms and automatic point selection the full six-dimensional HOOH PES can be fit over a range of 100 kcal/mol to an accuracy of less than 1 kcal/mol with similar to1350 ab initio points. (C) 2004 American Institute of Physics.

关键词： dynamics calculations

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Interaction of Metamitron and Fenhexamid with Ca²⁺-Montmorillonite Clay Surfaces: A Density Functional Theory Molecular dynamics Study

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JOURNAL OF COMPUTATIONAL CHEMISTRY 2019年第14期40卷 1449-1462页

作者： Belzunces, Bastien Hoyau, Sophie Bessac, Fabienne Univ Toulouse Lab Chim & Phys Quant IRSAMC UPS Toulouse France CNRS UMR 5626 Toulouse France Univ Toulouse INPT Ecole Ingn Purpan Toulouse 03 France

Metamitron (Meta), an herbicide, and fenhexamid (Fen), a fungicide, are authorized by the European Union to be used in agriculture. This article reports theoretical calculations about Meta and Fen in interaction with a clay surface: a Ca-montmorillonite (Mont). Conformational searches have been performed thanks to Car-Parrinello molecular dynamics simulations from which geometries have been extracted. Interaction and adsorption energies have been calculated for isomers of Meta or Fen in interaction with Mont to understand the relative stability of various kinds of complexation. Substantial adsorption energies are comparable for Meta and Fen: around -40 kcal/mol. For Fen-Mont, the CO monodentate family is surprisingly the lowest in energy. Moreover, the 10 lowest-energy isomers involve complexation on Fen carbonyl oxygens. The Meta-Mont lowest-energy family, N-N, does not involve pi delocalization breaking within Meta. At the same time, the stronger the interaction energy is, the larger the structural modifications within Mont are, particularly concerning the interacting cation distance to the surface. The non-negligible charge transfer and the magnitude of the adsorption energy speak in favor of the chemisorption of the pesticide on the surface. (c) 2019 Wiley Periodicals, Inc.

关键词： pesticide metamitron fenhexamid pesticide-montmorillonite isomers dynamics calculations adsorption energy

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Semiclassical wave packet study of anomalous isotope effect in ozone formation

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JOURNAL OF CHEMICAL PHYSICS 2007年第15期127卷 154312-1-154312-1页

作者： Vetoshkin, Evgeny Babikov, Dmitri Marquette Univ Dept Chem Wehr Chem Bldg Milwaukee WI 53201 USA

We applied the semiclassical initial value representation method to calculate energies, lifetimes, and wave functions of scattering resonances in a two-dimensional potential for O+O-2 collision. Such scattering states represent the metastable O-3(*) species and play a central role in the process of ozone formation. Autocorrelation functions for scattering states were computed and then analyzed using the Prony method, which permits one to extract accurate energies and widths of the resonances. We found that the results of the semiclassical wave packet propagation agree well with fully quantum results. The focus was on the (OOO)-O-16-O-16-O-18 isotopomer and the anomalous isotope effect associated with formation of this molecule, either through the (OO)-O-16-O-16+O-18 or the O-16+(OO)-O-16-O-18 channels. An interesting correlation between the local vibration mode character of the metastable states and their lifetimes was observed and explained. New insight is obtained into the mechanism by which the long-lived resonances in the delta zero-point energy part of spectrum produce the anomalously large isotope effect. (C) 2007 American Institute of Physics.

关键词： POTENTIAL-ENERGY SURFACE COLLISION-INDUCED DISSOCIATION INITIAL-VALUE METHOD RATE COEFFICIENTS dynamics calculations INTRAMOLECULAR THEORY PRESSURE-DEPENDENCE MOLECULAR-dynamics METASTABLE STATES AB-INITIO

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Semiclassical wave packet study of ozone forming reaction

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JOURNAL OF CHEMICAL PHYSICS 2006年第2期125卷 24302-1-24302-页

作者： Vetoshkin, Evgeny Babikov, Dmitri Marquette Univ Dept Chem Milwaukee WI 53201 USA

We have applied the semiclassical wave packet method (SWP) to calculate energies and lifetimes of the metastable states (scattering resonances) in a simplified model of the ozone forming reaction. All values of the total angular momentum up to J=50 were analyzed. The results are compared with numerically exact quantum mechanical wave packet propagation and with results of the time-independent WKB method. The wave functions for the metastable states in the region over the well are reproduced very accurately by the SWP;in the classically forbidden region and outside of the centrifugal barrier, the SWP wave functions are qualitatively correct. Prony's method was used to extract energies and lifetimes from the autocorrelation functions. Energies of the metastable states obtained using the SWP method are accurate to within 0.1 and 2 cm(-1) for under-the-barrier and over-the-barrier states, respectively. The SWP lifetimes in the range of 0.5

关键词： POTENTIAL-ENERGY SURFACE COLLISION-INDUCED DISSOCIATION RATE COEFFICIENTS dynamics calculations INTRAMOLECULAR THEORY PRESSURE-DEPENDENCE ISOTOPE DEPENDENCE METASTABLESTATES TRANSITION-STATE RECOMBINATION

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Computer experiments on dynamical cloud and space time fluctuations in one-dimensional meta-equilibrium plasmas

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PHYSICS OF PLASMAS 1996年第7期3卷 2538-2545页

作者： Rouet, JL Feix, MR Laboratoire de Mathématique Appliquée et de Physique Mathématique d'Orléans CNRS‐Université d'Orléans UFR Sciences rue de Chartres 45067 Orléans Cedex 2 France

The test particle picture is a central theory of weakly correlated plasma. While experiments and computer experiments have confirmed the validity of this theory at thermal equilibrium, the extension to meta-equilibrium distributions presents interesting and intriguing points connected to the under or over-population of the tail of these distributions (high velocity) which have not yet been tested. Moreover, the general dynamical Debye cloud (which is a generalization of the static Debye cloud supposing a plasma at thermal equilibrium and a test particle of zero velocity) for any test particle velocity and three typical velocity distributions (equilibrium plus two meta-equilibriums) are presented. The simulations deal with a one-dimensional two-component plasma and, moreover, thr:relevance of the check for real three-dimensional plasma is outlined. Two kinds of results are presented: the dynamical cloud itself and the more usual density (or energy) fluctuation spectrums, Special attention is paid to the behavior of long wavelengths which needs long systems with very small graininess effects and, consequently, sizable computation efforts. Finally, the divergence or absence of energy in the small wave numbers connected to the excess or lack of fast particles of the two above mentioned meta-equilibrium is exhibited. (C) 1996 American Institute of Physics.

关键词： dynamics calculations PLASMA SIMULATION COMPUTERIZED SIMULATION TEST PARTICLES BOLTZMANN?VLASOV EQUATION DISTRIBUTION FUNCTIONS FLUCTUATIONS

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Semiclassical initial value representation treatment of a hydrogen bonded complex of rigid water molecules from a single trajectory in Cartesian coordinates

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JOURNAL OF CHEMICAL PHYSICS 2007年第14期127卷 144306-1-144306-4页

作者： Issack, Bilkiss B. Roy, Pierre-Nicholas Univ Alberta Dept Chem Edmonton AB T6G 2G2 Canada

A semiclassical initial value representation approach for molecular systems in Cartesian coordinates is combined with a recently proposed time averaging technique [J. Chem. Phys. 118, 7174 (2003)]. It is shown that a single trajectory can yield the zero-point energy of the water dimer with good accuracy for the model chosen when compared to fully constrained Cartesian semiclassical calculations. The convergence with respect to the number of averaging time origins is discussed. (c) 2007 American Institute of Physics.

关键词： VIBRATIONAL-ENERGY LEVELS GEOMETRIC CONSTRAINTS INFLUENCE FUNCTIONALS dynamics calculations TIME SYSTEMS OPTIMIZATION SIMULATIONS PROPAGATOR

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