Time-dependent quantum wave packet study of H+HCN→H2+CN reaction

Time-dependent quantum wavepacket calculations for the H+HCN reaction are carried out on the ab initio potential energy surface of ter Horst [J. Chem. Phys. 105, 558 (1996)]. The dynamics calculations are performed using both the semirigid vibrating rotor target (SVRT) model [J. Chem. Phys. 111, 3929 (1999)] as well as the pseudo atom-diatom model. Total reaction probabilities from the initial ground state of the reagent are calculated for various values of the total angular momentum quantum number J. Reaction cross sections and rate constants are also calculated. The dynamical result from the SVRT calculation is compared with that from a pseudo atom-diatom calculation in which the HCN is treated as a pseudo diatom. Both the SVRT and pseudo atom-diatom calculations involve three degrees of freedom for the H+HCN reaction due to linearity of the HCN molecule at both reactant and transition states. The results from these two calculations are generally close to each other with some difference at high collision energies. The two models for the current system are essentially the same except that the rotational constant used is different. In particular, the SVRT model uses the correct rotational constant for the linear HCN molecule while the pseudo atom-diatom model produces a rotational constant which is much larger than the correct one. (C) 2002 American Institute of Physics.