Competition between mixing and segregation in bimetallic AgnRbn clusters (n=2-10)
Can. J. Chem. 87 (7), 1013-1021, July 2009
Submitted to Cluster Science: 4 November 2009
Last Update: 6 January 2011

10.1139/V09-065
OA Status: unknown

Abstract

We found the minimum-energy structures of AgnRbn (n = 2–10) clusters by a combination of density functional theory (DFT) and taboo search global optimization. The global minimum geometry is mixed for n ≤ 4 and segregated, with a core-shell arrangement, for n > 4. There is a change in the nature of the bonding, from ionic to metallic, between n = 4 and n = 5. Although metallic bonding dominates at n > 4, large atomic charges (in the order of ±0.5) persist. These atomic charges (negative on the interior Ag atoms, positive on the surface Rb atoms) make AgnRbn clusters analogous to Zintl compounds and could prevent them from coalescing. This makes them intriguing potential building blocks for cluster-assembled materials. Ag4Rb4 is relatively stable compared with other AgnRbn clusters; it has a nearly cubic shape, a large HOMO–LUMO gap (2 eV), and a highly ionic character with atomic charges equal to roughly ±1 au.

Classifications

Document Type theoretical
Research Field Geometric Structures