Accurate quantum thermal rate constants for the three-dimensional H+H/sub 2/ reaction
The rate constants for the three-dimensional H+H/sub 2/ reaction on the Liu--Siegbahn--Truhlar--Horowitz (LSTH) surface are calculated using Pack--Parker hyperspherical (APH) coordinates and a /ital C//sub 2/ital v// symmetry adapted direct product discrete variable representation (DVR). The /ital C//sub 2/ital v// symmetry decomposition and the parity decoupling on the basis are performed for the internal coordinate xi. The symmetry decomposition results in a block diagonal representation of the flux and Hamiltonian operators. The multisurface flux is introduced to represent the multichannel reactive flux. The eigenvalues and eigenvectors of the /ital J/=0 internal Hamiltonian are obtained by sequential diagonalization and truncation. The individual symmetry blocks of the flux operator are propagated by the corresponding blocks of the Hamiltonian, and the /ital J/=0 rate constant /ital k//sup 0/(/ital T/) is obtained as a sum of the rate constants calculated for each block. /ital k//sup 0/(/ital T/) is compared with the exact /ital k//sup 0/(/ital T/) obtained from thermal averaging of the /ital J/=0 reaction probabilities; the errors are within 5%--20% up to /ital T/=1500 K. The sequential diagonalization--truncation method reduces the size of the Hamiltonian greatly, but the resulting Hamiltonian matrix still describes the time evolution very accurately. For the /ital J//ne/0 rate constant calculations, the truncated internal Hamiltonian eigenvector basis is used to construct reduced (/ital JK//sub /ital J//) blocks of the Hamiltonian. The individual (/ital JK//sub /ital J//) blocks are diagonalized neglecting Coriolis coupling and treating the off-diagonal /ital K//sub /ital J//+-2 couplings by second order perturbation theory. The full wave function is parity decoupled. The rate constant is obtained as a sum over /ital J/ of (2/ital J/+1)/ital k//sup /ital J//(/ital T/).
- Research Organization:
- The Department of Chemistry and the James Franck Institute, The University of Chicago, Chicago, Illinois 60637(US)
- OSTI ID:
- 6047639
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 91:2
- Country of Publication:
- United States
- Language:
- English
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