Global potential-energy surfaces for H₂Cl

We present two new analytic potential-energy surfaces suitable for studying the competition between the abstraction reaction H + DCl→HD + Cl and the exchange reaction H + DCl→HCl + D. In the abstraction channel the surfaces are only slightly different from the Stern-Persky-Klein GSW surface, but the exchange barrier on both surfaces is raised by inclusion of a three-center term fitted to ab initio extended-basis-set multireference configuration interaction calculations with scaled external correlation. The two surfaces differ significantly only for the steepness of H-Cl-H bend potential. The exchange and abstraction saddle points are characterized by harmonic analysis for H ₂Cl, HDCl, and D₂Cl, and we also compute vibrationally adiabatic barrier heights including anharmonicity. We also report thermal rate constants and activation energies for both reactions mentioned above.