Theoretical Ionization Energies and Geometries for Ni sub n (4 < = n < = 9)

• Published in: Journal of physical chemistry (1952) 1992-04, Vol.96 (9), p.3633-3640
• Main Authors: Nygren, M A, Siegbahn, P E M, Wahlgren, U, Akeby, H
• Format: Article
• Language: English
• ISSN: 0022-3654

Ionization energies for Ni clusters with four to nine atoms have been calculated and compared to recent experiments. Two different models have been tried, both of them relying on a clear identification of 3d derived and 4s,4p derived orbitals. In the first model, used previously for Cu clusters, all metal atoms are described as effective one-electron systems and a 4s,4p electron is ionized. In the second model, 3d ionization is considered by describing one metal atom at the all-electron level. It is shown that the second model is required to explain the absence of odd--even oscillations in the experimental ionization measurements. It is also argued that the fact that the outermost ionization sometimes occurs from a 3d orbital is not in conflict with a model where the 3d orbitals only make small contributions to the binding of the cluster. The calculations show, in agreement with experiment, that the Ni sub 6 cluster is the only one of the investigated clusters which has an ionization energy > 6.2 eV and which is thus out of reach for the laser source used in the experiments.