Atomistic and electronic structure of (X ₂ O ₃ ) _n nanoclusters; n =1–5, X=B, Al, Ga, In and Tl

Abstract

The stable and metastable, as measured using an all-electron density functional theory approach, stoichiometric clusters of boron, aluminium, gallium, indium and thallium oxide are reported. Initial candidate structures were found using an evolutionary algorithm to search the energy landscape, defined using classical interatomic potentials, for alumina and india followed by data mining or rescaling. Characterization of the refined structures was performed by electronic structure techniques at the hybrid density functional and many-body GW levels of theory. We make accurate predictions of the spectroscopic properties represented by mean ionization potentials of 11.4, 9.9, 9.8, 8.8 and 8.4 eV and electron affinities of 0.05, 1.1, 1.6, 1.9 and 2.5 eV for boria, alumina, gallia, india and thallia, respectively. The changes in the global minima, atomistic and electronic properties with respect to the cluster and cation size are discussed.

Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study

“…These values are very similar to previously reported structural parameters for small alumina clusters. 34,35 For example, the initial configuration of oxygen that develops in Al 4 Cp 4 (+O 2 ) is very close to the oxygen in the kite-shaped global minimum for an Al 2 O 3 cluster. 35 The values fall slightly below that of bulk α-Al 2 O 3 .…”

“…34,35 For example, the initial configuration of oxygen that develops in Al 4 Cp 4 (+O 2 ) is very close to the oxygen in the kite-shaped global minimum for an Al 2 O 3 cluster. 35 The values fall slightly below that of bulk α-Al 2 O 3 . [36][37][38] In the non-methylated Al 4 Cp 4 system, a second peak with high probability is found at 3.2 Å, very close to the average AlAl bond distance reported for bulk amorphous Al 2 O 3 .…”

Structure prediction of nanoclusters; a direct or a pre-screened search on the DFT energy landscape?

“…Mainstream global optimisation in the field of structure prediction is typically applied to searching the energy landscapes defined by interatomic potentials, and subsequently the better structures are refined at a higher level of theory, such as DFT. 32 With greater availability of structural data for bulk rather than nanoclusters, interatomic potential parameters are generally fitted to reproduce bulk properties. When the atomic structure of nanoclusters is predicted to be different to the local structure found within the bulk phase, then it may be beneficial to refine the interatomic potential parameters to reproduce DFT energy minima nanoclusters.…”

Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

“…22 Detailed structural information on gas phase clusters can be obtained from infrared photodissociation (IRPD) spectroscopy, but until now IRPD spectra have only been reported for the aluminum oxide cations [(Al 2 O 3 ) 1-4 (AlO)] + . 23 Electronic structure studies on smaller aluminum oxides containing up to two Al atoms have focused mainly on neutral [24][25][26][27][28][29][30][31][32][33][34] and to a lesser extent on anionic 7,26,27,[35][36][37] clusters. For AlO − , AlO 2 − , and AlO 4 − , closed-shell electronic ground states of 1 Σ + (C ∞v ), 1 Σ g (D ∞h ), and 1 A 1 (D 2d ) symmetry, respectively, have been predicted.…”