Broken-bond rule for the surface energies of noble metals

Using two different full-potential ab initio techniques we introduce a simple rule based on the number of broken first-neighbour bonds to determine the surface energies of the three noble metals Cu, Ag and Au. When one bond is broken, the rearrangement of the electronic charge for these metals does not practically lead to a change of the remaining bonds. Thus the energy needed to break a bond is independent of the surface orientation, so that the surface energy is in good approximation proportional to the number of broken nearest-neighbour bonds.