Interpolated ab initio quantum scattering for the reaction of OH with HCl

We present an interpolated ab initio quantum scattering (AIQS) approach to studying chemical reactions. The dynamics calculations were performed by solving the time-independent Schrodinger equation. The potential energy surface used was interpolated from a set of grid energy points by a generalized discrete variable representation method. The guided spectral transform technique developed by the authors and the single-sector hyperspherical projection method for boundary conditions were extended to the rotating bond approximation model. The AIQS approach has been applied to the OH+HCl --> Cl+H2O reaction, where the grid energy points were calculated by a dual level ab initio theory. The results obtained show that there exist a van der Waals complex in the entrance channel and an early saddle point with nonplanar geometry. Calculated thermal rate constants are in good agreement with the experimental results. They are nearly temperature-independent at low temperatures (T < 300 K) while a sharp increase with temperature is observed at higher temperatures. In addition, it was found that the long range interaction potential plays an important role in the dynamics. (C) 2000 American Institute of Physics. [S0021-9606(00)01844-4].