The behavior of small atomic clusters on an (001) surface was studied by means of field ion microscopy. The clusters consisted of 8 atoms or 10 atoms. It was found that such clusters were energetically favored to form ring configurations with central lattice vacancies. The fact that atomic ring configurations with fewer nearest-neighbor bonds were more thermally stable, than dense cluster structures with more nearest-neighbor bonds, confirmed the assumed non-additivity of bond energies at the metal surface.

C.Chen, T.T.Tsong, S.Liang, L.Zhang: Philosophical Magazine Letters, 1995, 71[6], 357-65