An example for the above N21/3 scaling law is given by the calculated cohesive energy for magnesium clusters,3 which is the bond energy per atom, as shown in Fig. 3. Extrapolation
yields a bulk binding energy per atom of 1.39(1) eV, which is close to the experimental value of 1.51 eV. It is plausible that the cohesive energy scales the same way as the coordination
number, since each neighbouring atom forms one bond.It should be noted that the cohesive energy in Fig. 3 represents an average value. In reality, however, the atoms in the interior of the cluster are more highly coordinated, form more bonds and are therefore more stable than those at the cluster surface. For cubic crystals as those drawn in Fig