Topography of potential-energy surfaces. DIM (diatomics-in-molecules) surface for F + F2

Abstract

Potential-energy surfaces have been calculated over the full range of nuclear configurations for the F + F₂ reaction using the DIM (diatomics-in-molecules) method with the 28 polyatomic basis functions of ²A′ symmetry and the 26 of ²A″ symmetry arising from three F(²P_u) atoms. The lowest ²A′ surface has its lowest potential-energy barrier E_b≈ 72 kJ mol^–1 in a configuration bent by ca. 30 ° from the collinear configuration with ²Σ⁺_g symmetry. The lowest ²A″ surface has its lowest barrier E_b≈ 108 kJ mol^–1 in the collinear configuration with ²Π_u symmetry. The lowest ²A″ surface shows a stronger preference for the collinear configuration than does the lowest ²A′ surface, in accordance with the predictions of Walsh molecular-orbital theory.