Articles you may be interested inCross sections and rate constants for OH + H2 reaction on three different potential energy surfaces for rovibrationally excited reagents J. Chem. Phys. 135, 194302 (2011); 10.1063/1.3660222 Predicting observables on different potential energy surfaces using feature sensitivity analysis: Application to the collinear H+H2 exchange reaction J. Chem. Phys. 97, 6240 (1992); 10.1063/1.463685 Distributed complex Gaussian basis sets: A useful function space for the solution of predissociation problems via the complex eigenvalue Schrödinger equation. Application to the isotope effect of NeH, NeD J. Chem. Phys. 93, 6642 (1990); 10.1063/1.458932 Potential energy surface for the collinear reaction of Ne and HeHThree different functional forms are fit to a calculated coupled electron pair approach potential energy surface for the reaction Ne+Ht ..... NeH+ +H. Minimum energy pathways and stationary points of the various fits are discussed.represents the H-H distance.
Theoretical studies of the reactivity and spectroscopy of H+CO=HCO. I. Stabilization and scattering studies of resonances for J=0 on the Harding a b i n i t i o surfaceThe bending-corrected rotating linear model (BCRLM) is used to investigate the reaction of neon with Hi (v=0-3) using three different fits to the ab initio potential-energy surface computed by Urban, Jaquet, and Staemmler. Numerous long-liy~d scattering resonances are found for each surface. The number and position of these scattering resonances are found to be sensitive to the relatively small differences among these three surfaces. These BCRLM results demonstrate how the rich resonance structure that appears in the partial cross sections is washed out in the total cross section. The integrated rates for reactivity from v=O and 1 are nearly identical for all three potential-energy surfaces over a wide range of temperatures. However, the integrated rates from v=2 and 3 exhibit significant differences among the potential-energy surfaces. A vibrationally adiabatic hyperspherical model of the trapped resonance states provides insight into the nature and contribution of these resonances to reactive scattering. The more accurate of the three fits to the ab initio potential-energy surface (obtained using the functional form of Aguado and Paniagua) is also used to obtain converged results for total angular momentum J=O employing the adiabatically adjusting, principal axis, hyperspherical (APH) formulation of Pack and Parker for quantum reactive scattering in three dimensions (3D). An eigenlifetime analysis of these 3D scattering results reveals numerous resonances with lifetimes of 1 ps or more. While this resonance structure is sensitive to the details of the potential energy surface, with appropriate Gaussian averaging over the total scattering energy, the cumulative reaction probabilities (CRPs) are not very sensitive to changes in the potential energy surface. Moreover, these quantum CRPs agree rather well with CRPs predicted using variational Rice-Ramsperger-Kassel-Marcus (RRKM) calculations.2728
Unrestricted Hartree-Fock, coupled-cluster calculations are reported for the ground state of NeH' using atomic basis sets of increasing size and accuracy for both Ne and H. The goal is to determine the basis set and coupled-cluster level of calculation needed to obtain a NeH' potential energy curve of known accuracy. Here, it is shown that calculations using a quintuple zeta basis at the coupled-cluster singles and doubles level with noniterative triples, CCSD(T), predict a Ne-H bond dissociation energy that is within about 0.01 eV of the exact Born-Oppenheimer molecular electronic structure result. Spectroscopic constants determined using the Simons-Parr-Finlan procedure are found to be in very good agreement with the experimental results. Calculations at the augmented quadruple zeta level for the two lowest triplet excited states of the NeH' species are presented. Both of these states separate into ground-state Ne' and H(1s). The resulting potential curves predict stable minima at the SCF, CCSD, and CCSD(T) levels with dissociation energies of about 0.07 eV. Spectroscopic constants from the potential curves and dissociation constants are reported.
The Parker and Pack method for calculating accurate three-dimensional reactive scattering information uses adiabatically adjusting, principal axes hyperspherical (APH) coordinates to reduce the three-dimensional Schrödinger equation to a set of coupled equations in the hyperradius ρ. Solution of these coupled equations in the usual manner produces the scattering S matrix for the three-atom system of interest. To obtain these coupled equations it is necessary to solve a series of two-dimensional Schrödinger equations on the surface of a hypersphere defined by the hyperspherical polar and azimuthal angles θ and χ, respectively. In this paper, the computational advantages of the direct method for obtaining the energy derivatives of the S matrix are further documented using both the discrete variable representation and the analytical basis method of Pack and Parker for obtaining surface functions. Detailed studies of the title reaction are used to explore various operational criteria to assure that the predicted scattering results such as state-to-state transition probabilities and time delays are converged to the extent desired. It is also shown that the Hermitian property of the Smith lifetime matrix Q, which is accurately produced with the direct energy derivative method, is often not preserved when numerical energy derivatives are employed.
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