PHYSICS OF NICKEL CLUSTERS - 2 - ELECTRONIC-STRUCTURE AND MAGNETIC-PROPERTIES

Using a combination of classical molecular dynamics simulation and fir st principles molecular orbital theory, we provide the first comprehen sive study of the equilibrium geometries, energetics, electronic struc ture, vertical ionization potential, and magnetic properties of Ni clu sters containing up to 21 atoms. The molecular dynamics simulation mak es use of a tight binding many-body potential, while the calculations based on molecular orbital theory are carried out self-consistently us ing the numerical atomic bases and the density functional theory. The adequacy of the molecular dynamics results on the energetics and equil ibrium geometries is tested by comparing the results with those obtain ed from the self-consistent molecular orbital theory for clusters of u p to six atoms. For larger clusters, equilibrium geometries were obtai ned from molecular dynamics simulation, and their electronic structure and properties were calculated using molecular orbital theory without further geometry reoptimization. Frozen core and local spin density a pproximations were used in the molecular orbital calculations. In smal l clusters (n less than or equal to 6), the calculations were repeated by including all electrons and the gradient correction to the exchang e-correlation potential. The calculated vertical ionization potential and magnetic moments of Ni clusters are compared with recent experimen tal data.