On the calculation of atomic spin densities of hcp surface clusters of transition metals (Co, Ni, Cu), of medium size (100-1000 atoms)

In the present work it is proposed a very general quantum theoretical approach, able to describe the electronic structure of big molecular systems, that have a large number of unpaired electrons. The feasibility of the method is established by calculating, at semi-empirical level, the (restricted) atomic spin densities of 90 hcp surface clusters, in the range 20-1000 atoms, for the Co, Ni, Cu metals. Agreement of atomic magnetizations (spin moments) with, both, the Stern-Gerlach magnetic deflection, and the magnetic circular dichroism experimental ones, is achieved. A better theoretical description, according to these experimental results, is provided for the surface of the Ni metal. Finally, it is found that there exists a small excess of electronic density in the surface of these metals. (C) 2003 Elsevier Science B.V. All rights reserved.