Surface Corrugation in the Dissociative Adsorption ofH2on Cu(100)

First-principles calculations of the potential energy surface for ${\mathrm{H}}_2$ dissociation on the Cu(100) surface are presented. The height of the transition state above the surface and energy barrier are mapped over the surface. A very marked surface corrugation is found. Normal mode frequencies at the transition state for two extreme dissociation geometries suggest that zero point energy contributes little to surface corrugation. The local density approximation predicts a zero minimum barrier. Gradient corrections greatly increase the barrier height, but have little effect on the surface corrugation.