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(2Pu) atoms. The lowest 2A′ surface has its lowest potential-energy barrier Eb≈ 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 Eb≈ 108 kJ mol–1 in the collinear configuration with 2Πu 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.