Al_nBi Clusters: Transitions Between Aromatic and Jellium Stability

Abstract

An experimental and theoretical study of bismuth-doped aluminum clusters in the gas phase has revealed two particularly stable clusters, namely, Al(3)Bi and Al(5)Bi. We show that their electronic structure can be understood in terms of the aromatic and "Jellium" models, respectively. Negative ion photodetachment spectra provide a fingerprint of the electronic states in Al(n)Bi(-) (n = 1-5) anions, while theoretical investigations reveal the nature of the electronic orbitals involved. Together, the findings reveal that the all-metal Al(3)Bi cluster with 14 valence electrons is a cyclic, planar structure with a calculated large ionization potential of 7.08 eV, a low electron affinity of 1.41 eV, and a large gap of 1.69 eV between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO gap). The Al(3)Bi cluster has molecular orbitals reminiscent of aromatic systems and is a neutral cluster with no need for counterion or ligand support. A slightly larger cluster, Al(5)Bi, has 20 valence electrons and is another highly stable compact structure with a calculated large ionization potential of 6.51 eV and a large HOMO-LUMO gap of 1.15 eV. This cluster's stability is rooted in a Jellium electronic shell closing. The formation of stable species using aromatic bonding allows us to extend the idea of cluster-assembled materials built out of stable clusters with Jellium shell closings (superatoms) to include ones involving aromatic building blocks.

<I>Ab Initio</I> Study of Structural and Electronic Properties of Al<SUB><I>n</I></SUB>N (<I>n</I> = 1–22) Clusters

“…Al 3 Sb and Al 3 Bi have been predicted to have C 2v structure. 29 Al 4 N is found to stabilize as a N centered trapezium (C 2v symmetry) with Al-N bond distance varying from 1.95 Å to 2.06 Å which is consistent with existing 74 For n < 5, N tends to occupy a planar position and as a result the coordination number increases.…”

“…The ab initio calculations using B3LYP functional reported by Guo and Wu 26 had predicted D 3h state for Al 3 P with P atom occupying an internal position. Jones et al 29 reported the planar C 2v structure as the lowest energy structure for the same system. Al 3 Sb and Al 3 Bi have been predicted to have C 2v structure.…”

“…[2][3][4] Till date Al n clusters have been successfully doped as Al n X with X = H, 5 Na, 6 7 K, Rb, Cs, [8][9][10] Li, [11][12][13][14] Cu, 15 Au, Ag, 16 C, 17 18 O, 19 N, 20-25 P, 26 Si, 27 28 Bi, 29 Sb, Pb and Ge, 30 As 31 32 and halogens (F, Cl, Br, I). 33 They have been investigated using mass spectroscopy, anion photoelectron spectroscopy and photoionization spectroscopy.…”

Cage Structure Formation of Singly Doped Aluminum Cluster Cations AlnTM+(TM= Ti, V, Cr)

“…Computations on cationic transition metal doped aluminum clusters have only been performed for Al n Bi + exhibiting the 2D→3D transition at n+1=4→5 [33], while for neutral Al n Zn clusters the transition was predicted to occur at n+1=5→6 [34] and for neutral Al n Y m at sizes between n+1=3→4 and n+1=5→6, depending on the yttrium content [17]. Therefore, it can be assumed that also for the doped aluminum clusters Al n Ti + , Al n V + , and Al n Cr + the structural 2D→3D transition occurs at very small cluster sizes, even smaller than the smallest size for which we see Ar-complex formation in the current experiment.…”

Experimental and theoretical investigation on binary anionic clusters of AlmBi

“…Clusters consisted of III–V semiconductor elements have been the subject of experimental1–5 and theoretical6–12 studies. A primary driving force for such studies is that the materials with III–V elements are of great technological importance in the fabrication of fast microelectronic devices, small devices and light‐emitting diodes.…”