One-electron pseudopotential study of NanFn−1 clusters (2⩽n⩽29). I. Electronic and structural properties of the ground state

Abstract

We introduce a one-electron pseudopotential model to study the structural and electronic properties of excess-electron alkali halide clusters. This model assumes total charge transfer between alkali and halide atoms. This ionic part of the system is described via repulsive and Coulomb potentials. The remaining electrons of the excess metal atoms are treated within an explicit quantal scheme via ion–electron pseudopotentials. Moreover, explicit core-polarization and core-electron correlation contributions are taken into account. This model is used to derive ground state structural, energetics, and electronic properties of one-excess electron NanFn−1 clusters in the range 2⩽n⩽29. We show that the structural characters are closely related with electron localization and we propose a classification into five types, two of them exhibiting rather strong localization namely F-centers and Na-tail structures, the others exhibiting a less bound electron localizing in a surface-state, an edge-state, or on an atom-depleted face of the cluster. Although we observe an energetical predominance of cubiclike structures, hexagonal isomers are seen to appear as stable ones and exhibit similar localization features. The various energy contributions to the stability are examined. All studied NanFn−1 clusters are found stable with respect to fragmentation. The ionization potentials, which are seen to reflect faithfully the localization character, are discussed in details and compared with consistent recent experimental data.