Evolution to magnetic metallic properties. Some examples

3 Evolution to magnetic metallic properties. Some examples 

Although the extreme screening of the surface might initially seem surprising, it 

The addition of the CO shell to the Ni metal cores is found to have dramatic effects on the magnetism. The magnetic moments of the surface Ni atoms are completely quenched, those of the core atoms still remain at a sizable value of 0.5 per atom. These results are in keeping with previous calculations on smaller clusters, from which it could be concluded that carbonylation of Ni clusters so small as to have only surface atoms leads to a complete suppression of the magnetic moment of the cluster. The quenching of the Ni moments because of interaction with CO molecules is an effect which also occurs when CO is chemisorbed on to Ni metal surfaces. The electronic mechanism behind this effect is ascribed to a transfer 

The net result of this ligand-induced transfer mechanism can be interpreted as a change in the electronic structure of the surface atoms into a formal 3d -like atomic configuration (diamagnetic). The volume Ni atoms, on the other hand, retain most of their original 3d 4s character, so that they still show magnetic behavior similar to that of the bulk metal. 

As was mentioned in Section 4.V.2.2, the Pauli susceptibility of bulk Pd is exchange-enhanced by a Stoner factor S = 9.4. Its temperature-dependence is a result of marked energy-dependence in the density of states. The susceptibility of the clusters is indeed indicative of enhancement of the Pauli susceptibility, but one which is reduced. Temperature-dependence is also observed, again reduced relative to that of the bulk. The size-dependence was described with a model which assumes a reduction of the density of states at the cluster surface as a result of the ligand bonding, by analogy with similar effects on nickel surfaces, as described above. Accordingly, the susceptibility without enhancement effects was taken to depend on 

---