A theoretical study of the potential energy surface for O(3P)+H2

Abstract

Barrier heights and transition state geometries have been calculated for the reaction O(³P)+H₂→OH+H using large scale POL‐CI wave functions (based on GVB wave functions using basis sets of up to triple zeta valence plus double zeta polarization quality). A detailed study was made of the effects on the calculated barrier height and saddle point geometry of (i) basis set, (ii) choice of orbitals, and (iii) choice of reference configurations. Calculations using a [4s3p2d/3s2p] basis lead to a collinear saddle point with r_HH=0.92 Å and r_OH=1.23 Å with a corresponding barrier height of 12.5 kcal/mole. There are two surfaces which connect the reactants with the products: one of ³A′ symmetry and one of ³A^″ symmetry (these correspond to the two degenerate components of the ³Π state in collinear geometries). In the transition state region, the ³A′ surface has a steeper bending curve than the ³A^″ surface leading to significantly different reaction rates on the two surfaces.