The potential energy surface for dissociation of N2 on W(1 0 0)

Electronic total energy methods have been used to compute the potential energy surface for the dissociation of nitrogen molecules on the (1 0 0) face of tungsten. The dissociation is found to be activated, but there are also deep molecular chemisorption wells into which molecules may steer and trap. The molecular geometries in these precursor states agree well with experimental assignments. The dominant well is for the adsorption of a molecule oriented vertically on the atop site. An analysis of the bonding there indicates that the orbitals break into components largely located on either the inner or the outer N atom, rather than the standard Blyholder model. Dissociation paths are suggested based on several steps, passing through at least two molecular precursor states.