Transition-State Energy and Geometry, Exothermicity, and van der Waals Wells on the F + H₂ → FH + H Ground-State Surface Calculated at the r₁₂-ACPF-2 Level

Explicitly correlated averaged coupled-pair functional methods have been used to compute the ground-state Born-Oppenheimer potential energy surface for the F + HH' --> FH + H' reaction at the F + HH' and FH + H' asymptotes, the F...HH', and FH...H van der Waals wells, the reaction transition state, and at points along the intrinsic reaction coordinate connecting all of these stationary points. To these energies, corrections for spin-orbit coupling and scalar relativistic effects were added to produce total electronic energies whose accuracy is demonstrated to be very high (e.g., 0.1 kcal mol(-1)). The final data are used to refine the two-body parts of the currently best three-dimensional potential energy surface for this reaction, to predict several spectroscopic parameters of the species involved, and to offer accurate estimates of the title reaction's exothermicity (32.0 kcal mol(-1)) and activation barrier (1.8 kcal mol(-1)) as well as the geometry of the transition state.