Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. Computed p... more Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. Computed points to define a global potential energy surface. [The Journal of Chemical Physics 94, 7068 (1991)]. Stephen P. Walch, Ronald J. Duchovic. Abstract. ...
I. Introduction Bimolecular reactions of molecules containing hydrogen, carbon, oxygen, and nitro... more I. Introduction Bimolecular reactions of molecules containing hydrogen, carbon, oxygen, and nitrogen play an essential role in all hydrogen and hydrocarbon combustion processes occurring under atmospheric conditions. In particular, the reaction ... Graduate research assistant. ...
Canonical variational transition state theory is used to calculate bimolecular rate constants for... more Canonical variational transition state theory is used to calculate bimolecular rate constants for H + CH3 and D + CH3 recombination. The calculations are performed on an analytic potential energy surface derived from recent ab initio calculations. Rate constants calculated for this surface are in very good agreement with the experimental values. The H(D)---CH3 transitional rocking modes are treated as quantum harmonic oscillators or classical hindered rotors in the calculations. These two treatments give rate constants which agree to within 15%. The variational transition states become tighter as the temperature is increased.
A fully coupled realistic mode three-dimensional Hamiltonian representing the H–C–C→H+C=C dissoci... more A fully coupled realistic mode three-dimensional Hamiltonian representing the H–C–C→H+C=C dissociation is investigated semiclassically. This system has been found to exhibit quasiperiodic behavior above dissociation. Semiclassical vibrational eigenvalues and frequencies have been computed using the Sorbie–Handy method of semiclassical quantization.The semiclassical spectrum has also been computed from the autocorrelation function of the dynamical variable via a Fourier transform.
A Fourier transform method for calculating action variables and semiclassical eigenvalues in mole... more A Fourier transform method for calculating action variables and semiclassical eigenvalues in molecules starting from Cartesian coordinates and momenta is developed and applied to the determination of rotational semiclassical eigenvalues for rigid asymmetric top molecules. The method involves calculating rotational actions by using Fourier representations of the symmetric top action-angle variables to express the integrals. The question of what is the optimum quantization axis is considered, and it is found that the same primitive semiclassical eigenvalues are obtained independent of which principal axis is used for quantization provided that the replacement J → J+ 1/2 is made. The replacement J → [J(J+1)]1/2 leads to eigenvalues that are slightly dependent on quantization axis, but more accurate. For either choice of J replacement, the primitive eigenvalues are found to be double valued when trajectory motion is librational relative to both the prolate and oblate top quantization ax...
The Monte Carlo quasiclassical trajectory method is used to study the molecular dynamics of the H... more The Monte Carlo quasiclassical trajectory method is used to study the molecular dynamics of the H+CH3→CH4 association reaction. The bimolecular rate constant is calculated for a temperature of 300 K and compared with experimental measurements. Both the nature of the reactive trajectories and the bimolecular rate constant are very sensitive to the shape of the C–H stretching potential energy curve.
The variational transition state theory rate constant is calculated for the H+CH3 → CH4 bimolecul... more The variational transition state theory rate constant is calculated for the H+CH3 → CH4 bimolecular reaction and compared with the quasiclassical trajectory value reported previously. The calculations are performed on two different potential energy surfaces, MAPS/CH4-I and -II. To calculate the variational transition state theory rate constant, the reaction path and frequencies orthogonal to the reaction path are required. The general classical trajectory computer program mercury was modified to perform these calculations. Good agreement is found between the variational transition state theory and quasiclassical trajectory rate constants for both the MAPS/CH4-I and -II surfaces. The rate constants for the two surfaces differ by an order of magnitude. These calculated values are compared with a recent experimental measurement.
Erratum: Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. C... more Erratum: Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. Computed points to define a global potential energy surface [J. Chem. Phys. [bold 94], 7068 (1991)]. [The Journal of Chemical Physics 96, 4050 (1992)]. ...
Several ab initio studies have focused on the minimum energy path region of the hydroperoxyl pote... more Several ab initio studies have focused on the minimum energy path region of the hydroperoxyl potential energy surface (PES) [J. Chem. Phys. 88, 6273 (1988)] and the saddle point region for H-atom exchange via a T-shaped HO2 complex [J. Chem. Phys. 91, 2373 (1989)]. Further, the results of additional calculations [J. Chem. Phys. 94, 7068 (1991)] have been reported, which, when combined with the earlier studies, provide a global description (but not an analytic representation) of the PES for this reaction. In this work, information at the stationary points of the ab initio PES is used within the framework of conventional Transition State Theory (TST)/RRKM. Theory to compute estimates of the thermal termolecular rate coefficients for the reaction between the H(D) atom and O2 in the presence of two different bath gases, argon and nitrogen, as a function of pressure and temperature. These calculations span a pressure range from 1.0 Torr to the high-pressure limit and a temperature range ...
Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. Computed p... more Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. Computed points to define a global potential energy surface. [The Journal of Chemical Physics 94, 7068 (1991)]. Stephen P. Walch, Ronald J. Duchovic. Abstract. ...
I. Introduction Bimolecular reactions of molecules containing hydrogen, carbon, oxygen, and nitro... more I. Introduction Bimolecular reactions of molecules containing hydrogen, carbon, oxygen, and nitrogen play an essential role in all hydrogen and hydrocarbon combustion processes occurring under atmospheric conditions. In particular, the reaction ... Graduate research assistant. ...
Canonical variational transition state theory is used to calculate bimolecular rate constants for... more Canonical variational transition state theory is used to calculate bimolecular rate constants for H + CH3 and D + CH3 recombination. The calculations are performed on an analytic potential energy surface derived from recent ab initio calculations. Rate constants calculated for this surface are in very good agreement with the experimental values. The H(D)---CH3 transitional rocking modes are treated as quantum harmonic oscillators or classical hindered rotors in the calculations. These two treatments give rate constants which agree to within 15%. The variational transition states become tighter as the temperature is increased.
A fully coupled realistic mode three-dimensional Hamiltonian representing the H–C–C→H+C=C dissoci... more A fully coupled realistic mode three-dimensional Hamiltonian representing the H–C–C→H+C=C dissociation is investigated semiclassically. This system has been found to exhibit quasiperiodic behavior above dissociation. Semiclassical vibrational eigenvalues and frequencies have been computed using the Sorbie–Handy method of semiclassical quantization.The semiclassical spectrum has also been computed from the autocorrelation function of the dynamical variable via a Fourier transform.
A Fourier transform method for calculating action variables and semiclassical eigenvalues in mole... more A Fourier transform method for calculating action variables and semiclassical eigenvalues in molecules starting from Cartesian coordinates and momenta is developed and applied to the determination of rotational semiclassical eigenvalues for rigid asymmetric top molecules. The method involves calculating rotational actions by using Fourier representations of the symmetric top action-angle variables to express the integrals. The question of what is the optimum quantization axis is considered, and it is found that the same primitive semiclassical eigenvalues are obtained independent of which principal axis is used for quantization provided that the replacement J → J+ 1/2 is made. The replacement J → [J(J+1)]1/2 leads to eigenvalues that are slightly dependent on quantization axis, but more accurate. For either choice of J replacement, the primitive eigenvalues are found to be double valued when trajectory motion is librational relative to both the prolate and oblate top quantization ax...
The Monte Carlo quasiclassical trajectory method is used to study the molecular dynamics of the H... more The Monte Carlo quasiclassical trajectory method is used to study the molecular dynamics of the H+CH3→CH4 association reaction. The bimolecular rate constant is calculated for a temperature of 300 K and compared with experimental measurements. Both the nature of the reactive trajectories and the bimolecular rate constant are very sensitive to the shape of the C–H stretching potential energy curve.
The variational transition state theory rate constant is calculated for the H+CH3 → CH4 bimolecul... more The variational transition state theory rate constant is calculated for the H+CH3 → CH4 bimolecular reaction and compared with the quasiclassical trajectory value reported previously. The calculations are performed on two different potential energy surfaces, MAPS/CH4-I and -II. To calculate the variational transition state theory rate constant, the reaction path and frequencies orthogonal to the reaction path are required. The general classical trajectory computer program mercury was modified to perform these calculations. Good agreement is found between the variational transition state theory and quasiclassical trajectory rate constants for both the MAPS/CH4-I and -II surfaces. The rate constants for the two surfaces differ by an order of magnitude. These calculated values are compared with a recent experimental measurement.
Erratum: Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. C... more Erratum: Theoretical characterization of the potential energy surface for H+O = HO = OH+O. III. Computed points to define a global potential energy surface [J. Chem. Phys. [bold 94], 7068 (1991)]. [The Journal of Chemical Physics 96, 4050 (1992)]. ...
Several ab initio studies have focused on the minimum energy path region of the hydroperoxyl pote... more Several ab initio studies have focused on the minimum energy path region of the hydroperoxyl potential energy surface (PES) [J. Chem. Phys. 88, 6273 (1988)] and the saddle point region for H-atom exchange via a T-shaped HO2 complex [J. Chem. Phys. 91, 2373 (1989)]. Further, the results of additional calculations [J. Chem. Phys. 94, 7068 (1991)] have been reported, which, when combined with the earlier studies, provide a global description (but not an analytic representation) of the PES for this reaction. In this work, information at the stationary points of the ab initio PES is used within the framework of conventional Transition State Theory (TST)/RRKM. Theory to compute estimates of the thermal termolecular rate coefficients for the reaction between the H(D) atom and O2 in the presence of two different bath gases, argon and nitrogen, as a function of pressure and temperature. These calculations span a pressure range from 1.0 Torr to the high-pressure limit and a temperature range ...
Uploads
Papers by Ronald Duchovic