Quantum-mechanical calculation of the thermal rate constant for the H2+Cl→ H+HClreaction

Accurate quantum calculations investigating the thermal rate constant and the cumulative reaction probability of the H-2 + Cl --> H + HCl reaction on a new three-dimensional ab initio potential energy surface are presented. Comparing experimental and calculated results, the barrier height of the new surface is found to be too large by about 0.23 meV (0.53 kcal/mol). Almost perfect agreement with experiment is obtained for an improved potential energy surface obtained by slightly scaling the correlation energy so that the dissociation energies of HCl and H-2 are reproduced accurately. Results of accurate calculations and results obtained within the modified J-shifting approximation agree within a 10% error margin. (C) 1999 Elsevier Science B.V. All rights reserved.