Abstract
Global analytic potential energy surfaces for collisions, including the hydrogen abstraction and hydrogen elimination channels, are presented. Ab initio electronic structure calculations were performed at the level with an one electron basis set. Approximately geometries were used to fit the three lowest triplet adiabatic states corresponding to the triply degenerate reactants. Transition state theory rate constant and total cross section calculations using classical trajectories to collision energies up to (collision velocity) were performed and show good agreement with experimental data. Flux-velocity contour maps are presented at selected energies for collisional excitation, , and channels to further investigate the dynamics, especially the competition and distinct dynamics of the two reactive channels. There are large differences in the contributions of each of the triplet surfaces to the reactive channels, especially at higher energies. The present surfaces should support quantitative modeling of collision processes up to .
P.F.C. and M.B. acknowledge support under Contract No. FA8718-05-C-0077.
I. INTRODUCTION
II. FITTING THE POTENTIAL SURFACES
A. Ab initio calculations
B. Potential energy surface fits
C. Properties of the fitted PESs
III. DYNAMICS RESULTS
A. Rate constants
B. QCT calculations
IV. CONCLUSIONS
Key Topics
- Surface states
- 49.0
- Surface reactions
- 26.0
- Hydrogen reactions
- 23.0
- Surface dynamics
- 22.0
- Electron surface collisions
- 21.0
Figures
Energy level diagram of the three lowest triplet electronic states of the system. The fitted surfaces examined in this work are indicated to the left of the vertical dashed line. The geometries of the transition structures TS1 and TS5 are given in atomic units and radians.
Energy level diagram of the three lowest triplet electronic states of the system. The fitted surfaces examined in this work are indicated to the left of the vertical dashed line. The geometries of the transition structures TS1 and TS5 are given in atomic units and radians.
The RMSD given in is plotted vs energy bin for (a) the S1 surface, (b) the S2 surface, and (c) the S3 surface.
The RMSD given in is plotted vs energy bin for (a) the S1 surface, (b) the S2 surface, and (c) the S3 surface.
Contour plots of the reaction. The S1, S2, and S3 state results for the calculations are given in (a), (b), and (c), respectively. The S1, S2, and S3 state results for the fitted PESs are given in (d), (e), and (f), respectively. The geometry is defined according to the TS1 transition state shown in Fig. 1. The (abscissa) and (ordinate) are varied to produce the energy contours. The energy zero corresponds to the equilibrium geometry of the separated reactants.
Contour plots of the reaction. The S1, S2, and S3 state results for the calculations are given in (a), (b), and (c), respectively. The S1, S2, and S3 state results for the fitted PESs are given in (d), (e), and (f), respectively. The geometry is defined according to the TS1 transition state shown in Fig. 1. The (abscissa) and (ordinate) are varied to produce the energy contours. The energy zero corresponds to the equilibrium geometry of the separated reactants.
Contour plots of the reaction. The S1, S2, and S3 state results for the calculations are given in (a), (b), and (c), respectively. The S1, S2, and S3 state results for the fitted PESs are given in (d), (e), and (f), respectively. The geometry is defined according to the TS5 transition state shown in Fig. 1. The (abscissa) and (ordinate) are varied to produce the energy contours. The energy zero corresponds to the equilibrium geometry of the separated reactants.
Contour plots of the reaction. The S1, S2, and S3 state results for the calculations are given in (a), (b), and (c), respectively. The S1, S2, and S3 state results for the fitted PESs are given in (d), (e), and (f), respectively. The geometry is defined according to the TS5 transition state shown in Fig. 1. The (abscissa) and (ordinate) are varied to produce the energy contours. The energy zero corresponds to the equilibrium geometry of the separated reactants.
The potential energy contours in Jacobi coordinates: (a) the S1, (b) the S2, and (c) the S3 electronic states of the PES of the current work; (d) the S1, (e) the S2, and (f) the S3 electronic states of Ref. 12. The triatom-atom Jacobi-like coordinate system of Ref. 26 is used as shown in the inset of (f), where is the distance from O atom to H, starts from the center of mass of , starts from the center of mass of , is the angle between and , and is the angle between and . All atoms are in the same plane, and the inset in (f) is not to scale. From the TS1 geometry given in Fig. 1, , , and are determined. With , , and fixed, the coordinates (abscissa) and (ordinate) are then varied to produce the contours.
The potential energy contours in Jacobi coordinates: (a) the S1, (b) the S2, and (c) the S3 electronic states of the PES of the current work; (d) the S1, (e) the S2, and (f) the S3 electronic states of Ref. 12. The triatom-atom Jacobi-like coordinate system of Ref. 26 is used as shown in the inset of (f), where is the distance from O atom to H, starts from the center of mass of , starts from the center of mass of , is the angle between and , and is the angle between and . All atoms are in the same plane, and the inset in (f) is not to scale. From the TS1 geometry given in Fig. 1, , , and are determined. With , , and fixed, the coordinates (abscissa) and (ordinate) are then varied to produce the contours.
Potential energy contours of (a) the S1, (b) the S2, and (c) the S3 electronic states of the PES of the current work and those of (d) the S1, (e) the S2, and (f) the S3 electronic states of Ref. 12. The reactant is fixed at the corresponding geometry of TS5 shown in Fig. 1 with the location of the attacking oxygen varying in the plane of the . Lengths are given in atomic units.
Potential energy contours of (a) the S1, (b) the S2, and (c) the S3 electronic states of the PES of the current work and those of (d) the S1, (e) the S2, and (f) the S3 electronic states of Ref. 12. The reactant is fixed at the corresponding geometry of TS5 shown in Fig. 1 with the location of the attacking oxygen varying in the plane of the . Lengths are given in atomic units.
Rate constants in as a function of temperature in Kelvin. The hydrogen abstraction reaction is denoted with black lines and the elimination reaction is denoted with red lines. The filled circles are the current work, the filled triangles are the previous results from Ref. 12, the open squares are the experimental results of Ref. 29, the open diamonds are the experimental results of Ref. 28, and the open left triangles are derived from the computational results of Ref. 14. Note that the reaction rates of the elimination reaction are multiplied by 1000 for visualization purposes.
Rate constants in as a function of temperature in Kelvin. The hydrogen abstraction reaction is denoted with black lines and the elimination reaction is denoted with red lines. The filled circles are the current work, the filled triangles are the previous results from Ref. 12, the open squares are the experimental results of Ref. 29, the open diamonds are the experimental results of Ref. 28, and the open left triangles are derived from the computational results of Ref. 14. Note that the reaction rates of the elimination reaction are multiplied by 1000 for visualization purposes.
(a) The total calculated cross sections as a function of collision energy in for the hydrogen abstraction reaction (black lines) and hydrogen elimination reaction (red lines). The filled circles are the current work, the filled triangles are the previous results from Ref. 12, the filled squares are the computational results of Ref. 7, and the open diamonds are the experimental results of Ref. 7. (b) The unweighted state resolved abstraction (black) and elimination (red) cross sections for the S1 state (solid lines), S2 state (dashed lines), and S3 state (dotted lines).
(a) The total calculated cross sections as a function of collision energy in for the hydrogen abstraction reaction (black lines) and hydrogen elimination reaction (red lines). The filled circles are the current work, the filled triangles are the previous results from Ref. 12, the filled squares are the computational results of Ref. 7, and the open diamonds are the experimental results of Ref. 7. (b) The unweighted state resolved abstraction (black) and elimination (red) cross sections for the S1 state (solid lines), S2 state (dashed lines), and S3 state (dotted lines).
(a) Opacity functions for the hydrogen abstraction (black) and elimination (red) reactions plotted vs impact parameter in atomic units. The S1 state is shown in solid lines, the S2 state is shown in dashed lines, and the S3 state is shown in dotted lines. (b) Opacity function for the hydrogen abstraction reaction for our previous simulation, Ref. 12, plotted vs impact parameter in atomic units. The S1 state is the solid line, the S2 state is the dashed line, and the S3 state is the dotted line.
(a) Opacity functions for the hydrogen abstraction (black) and elimination (red) reactions plotted vs impact parameter in atomic units. The S1 state is shown in solid lines, the S2 state is shown in dashed lines, and the S3 state is shown in dotted lines. (b) Opacity function for the hydrogen abstraction reaction for our previous simulation, Ref. 12, plotted vs impact parameter in atomic units. The S1 state is the solid line, the S2 state is the dashed line, and the S3 state is the dotted line.
Velocity-flux contours , in units of . (a) The differential cross section of the OOH elimination product at collision energy of . (b)–(c) The differential cross section active OH product (formed from the attacking O-atom) at a collision energies of 49.6 and , respectively. (d)–(f) The differential cross sections of for nonreactive collisions at energies of 16.2, 49.6, and , or collision velocities of 4, 7, and , respectively. Note in (d)–(f) the contour scale is logarithmic.
Velocity-flux contours , in units of . (a) The differential cross section of the OOH elimination product at collision energy of . (b)–(c) The differential cross section active OH product (formed from the attacking O-atom) at a collision energies of 49.6 and , respectively. (d)–(f) The differential cross sections of for nonreactive collisions at energies of 16.2, 49.6, and , or collision velocities of 4, 7, and , respectively. Note in (d)–(f) the contour scale is logarithmic.
Tables
Stationary point comparison between the fitted PES and the calculations for the reaction . All energies are given in relative to the reactant asymptote. The columns list energies of TS1 relative to the asymptote. The columns list energies of the product relative to the asymptote. Values in parentheses include zero-point correction. The geometry of the TS1 structure is given in Fig. 1 and is the same for each surface. Literature values are (a) Ref. 14 using from larger basis sets, (b) Ref. 7 using CCSD(T)/aug-cc-pVTZ, and (c) Ref. 5 which can be considered as benchmark.
Stationary point comparison between the fitted PES and the calculations for the reaction . All energies are given in relative to the reactant asymptote. The columns list energies of TS1 relative to the asymptote. The columns list energies of the product relative to the asymptote. Values in parentheses include zero-point correction. The geometry of the TS1 structure is given in Fig. 1 and is the same for each surface. Literature values are (a) Ref. 14 using from larger basis sets, (b) Ref. 7 using CCSD(T)/aug-cc-pVTZ, and (c) Ref. 5 which can be considered as benchmark.
Stationary point comparison between the fitted PES and the calculations for the reaction . All energies are given in relative to the reactant asymptote. The columns list energies of TS5 relative to the asymptote. The columns list energies of the product relative to the asymptote. Values in parentheses include zero-point correction. The geometry of the TS5 structure is given in Fig. 1 and is the same for the first two surfaces. Literature values are (a) Ref. 14 using from larger basis sets, (b) Ref. 7 using CCSD(T)/aug-cc-pVTZ, (c) Ref. 6 which can be considered as benchmark, and (d) Ref. 6 for S1 (Ref. 18).
Stationary point comparison between the fitted PES and the calculations for the reaction . All energies are given in relative to the reactant asymptote. The columns list energies of TS5 relative to the asymptote. The columns list energies of the product relative to the asymptote. Values in parentheses include zero-point correction. The geometry of the TS5 structure is given in Fig. 1 and is the same for the first two surfaces. Literature values are (a) Ref. 14 using from larger basis sets, (b) Ref. 7 using CCSD(T)/aug-cc-pVTZ, (c) Ref. 6 which can be considered as benchmark, and (d) Ref. 6 for S1 (Ref. 18).
Reaction rate constant parameters for the hydrogen abstraction and elimination reactions fit to the Arrhenius equation, for the computed reaction rates in the temperature range of 500–4000 K for products and 1500–4000 K for products.
Reaction rate constant parameters for the hydrogen abstraction and elimination reactions fit to the Arrhenius equation, for the computed reaction rates in the temperature range of 500–4000 K for products and 1500–4000 K for products.
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