Mercury adsorption on Ni{100}

Structural, kinetic and thermodynamic studies have been made for mercury adsorbed on Ni{100}. Mercury adsorbs with an isosteric heat of adsorption of 115±15 kJ mol −1 at zero coverage. The isosteric heat of adsorption increases with increasing coverage reaching a maximum of 165±15 kJ mol −1 at 3.8×10 18 atoms m −2, after which it falls, reaching a value of 100±20 kJ mol −1 at 9.5×10 18 atoms m −2.A c(2×2) LEED patterns is formed at 8×10 18 atoms m −2 which transforms to an incommensurate structure, having the matrix notation (2.07/0.37 0.37/2.07) with three mercury atoms per unit mesh. A model is proposed in which the adsorbed mercury forms a two-dimensional gas with attractive interactions at low coverages. With increasing coverage the interactions become repulsive and a transition occurs to the immobile c(2×2) structure. The desorption kinetics are shown to be consistent with the equilibrium adsorption studies using this model.