Multidimensional Potential Energy Surface for ${\mathrm{H}}_2$ Dissociation over Cu(111)

We present ab initio density functional calculations within the generalized gradient approximation for ${\mathrm{H}}_2$ dissociating over Cu(111). The minimum barrier for dissociation is 0.5 eV and shows large corrugation within the unit cell and a strong dependence on the molecular orientation. Dissociation is predicted to depend strongly on translational, vibrational, and rotational degrees of freedom in accordance with experiment. We show that even for a noble metal, the $d$ electrons are important for the molecule-surface interaction.