Theoretical Study of the Stability of Ag<sub>N</sub><sup>2+</sup>, Ag<sub>N</sub><sup>+</sup>, Ag<sub>N</sub><sup>-</sup> and Na<sub>N</sub> Clusters as a Function of Size Using the Density-Functional Formalism

Chemical Physics 120, 239 - 247 (1988)

Theoretical Study of the Stability of AgN2+, AgN+, AgN- and NaN Clusters as a Function of Size Using the Density-Functional Formalism

L.C. Balbás, A. Rubio, J.A. Alonso, G. Borstel

The spherical jellium model and self-consistent density functional theory have been used to study the stability of AgN2+, AgN+, AgN, AgN and NaN clusters. Calculations using the local-density approximation for exchange and correlation have shown that the magic numbers of XN or XN (X = noble metal) clusters produced as secondary ions by bombarding noble metal films with rare gas ions can be explained as due to shell-closing effects of the valence electrons moving in an effective spherically symmetric cluster potential. However, the LDA is unable to describe some negative clusters: either very small ones or those with a nearly empty external shell. This drawback is overcome by using a non-local approximation to the exchange-correlation potential. Finally the study of the fragmentation of AgN2+ clusters reveals some deficiencies of the spherical jellium model, most likely due to two facts. The first one is that only the atomic 4s, 5s or 6s electrons (for Cu, Ag and Au respectively) are considered as “cluster electrons” while explicit account of the d electrons has been neglected in our work. Secondly, cigar shape deformations of the cluster, also neglected here, could help to minimize the electrostatic interaction between the two holes.

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