Eur. Phys. J. D (2017) 71: 191
https://doi.org/10.1140/epjd/e2017-80042-9

Regular Article

The stabilities and electron structures of Al-Mg clusters with 18 and 20 valence electrons^*

College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, P.R. China

^a e-mail: chenhs@nwnu.edu.cn

Received: 21 January 2017
Received in final form: 27 April 2017
Published online: 11 July 2017

Abstract

The spherical jellium model predicts that metal clusters having 18 and 20 valence electrons correspond to the magic numbers and will show specific stabilities. We explore in detail the geometric structures, stabilities and electronic structures of Al-Mg clusters containing 18 and 20 valence electrons by using genetic algorithm combined with density functional theories. The stabilities of the clusters are governed by the electronic configurations and Mg/Al ratios. The clusters with lower Mg/Al ratios are more stable. The molecular orbitals accord with the shell structures predicted by the jellium model but the 2S level interweaves with the 1D levels and the 2S and 1D orbitals form a subgroup. The clusters having 20 valence electrons form closed 1S²1P⁶1D¹⁰2S² shells and show enhanced stability. The Al-Mg clusters with a valence electron count of 18 do not form closed shells because one 1D orbital is unoccupied. The ionization potential and electron affinity are closely related to the electronic configurations; their values are determined by the subgroups the HOMO or LUMO belong to.