Molecular Orbital Interpretation of Magic Clusters with Non‐Magic Numbers

Abstract

Why are they magical? Mixed-metal clusters have very different electronic properties from simple metal clusters. The large MO splitting and reordering of Al clusters by Cs doping render the jellium description invalid and are responsible for the magic nature of the highly symmetric Al(12)Cs(-) and Al(11)Cs(2) (-) clusters (see picture).

Computational Cogitation of Cn@Al12 Clusters

“…In accordance with the spherical jellium model, [63] one would predict such a cluster to have a high(er) stability owing to the closed nature of its electronic shells. [10,64] Indeed, Leuchtner et al [65] demonstrated that whilst most aluminium clusters react strongly with oxygen, Al 13 À , Al 23 À and Figure 1. Optimised internal core-shell clusters.…”

“…As such, there will undoubtedly be deviations in the number of electrons required for forming a closed shell on moving between the unique clusters. Recent examples of atypical magic clusters include [Al (10)(11)(12) Cs ] À anions, [10] in which doping or attachment of a few (Cs) atoms significantly alters the electronic structure (large molecular orbital splitting and reordering effectively renders the jellium model invalid) with magic behaviour rationalised through detailed analysis of molecular orbital perturbations, and clusters such as Pu@C 24 satisfying the 32-electron principle, that is, the number of valence electrons corresponding to fully occupied spdf subshells for the central metal atom. [11] Recent reviews of nanoparticles touch on aspects spanning the entire nanotechnology spectrum, from synthesis and characterisation to the applications of these unique materials.…”

“…[17][18][19] Fast forward to the present day and one can find an evergrowing body of literature detailing the design and application of a vast array of hybrid nanoclusters in fields as diverse as biomedicine, [20][21][22][23][24][25][26][27] catalysis [28][29][30][31][32][33][34][35][36][37] and electronics. [38][39][40][41][42] Of most relevance to the results presented herein are the studies of core-shell systems comprising small cores ( 5 atoms) and relatively small shells ( 20 atoms), [2,10,[43][44][45][46][47][48][49][50][51][52] particularly those detailing the behaviour of doped Al 12 .…”

Crystal field effects on the reactivity of aluminum-copper cluster anions

“…Similarly, the surprisingly large HOMO-LUMO gaps at 38 electrons which are observed in Al 13 + and Al 12 Cs − can be explained by the hybridization and splitting of the 2P z and 1F z 3 states from the 2P and 1F subshells, in which the 2P z state is pushed up in energy to the next shell, and 1F z 3 is stabilized through hybridization. 36,37 At lower energies, the 1D z 2 is pushed up in energy and the 2S 2 is stabilized, resulting in a pronounced gap at 18 electrons. This is also consistent with the twofold degenerate states below this gap having E 1 irreducible representations and the state above this gap having A 1 symmetry, as shown in Fig.…”