Structure, bonding and redox properties of scandium oxide clusters, a model study

A systematic survey of scandium oxide molecules and clusters was performed by means of density functional theory (DFT). Various types of scandium to oxygen bonding were characterized. Main features of the resulting menagerie of stable gas phase species are: (1) a basic Sc2O2 molecule with rhombic [GRAPHICS] structure, (2) a highly symmetric Sc2O3 molecule with [GRAPHICS] structure and D-3h symmetry, (3) an Sc2O4 dimer, which is an O=Sc-O-O-Sc=O analogue to hydrogen peroxide, and (4) the most stable cluster of Sc2O4 stoichiometry. The latter can be understood as two Sc atoms bridged by two oxygen atoms and a peroxy unit, i.e. [GRAPHICS] Bond breaking in the peroxy bridge, forming [GRAPHICS] can be used as a model for O-2 dissociation on an early transition metal oxide surface. The formation of ionic species was also investigated, and for all the oxide systems both cationic and anionic species were found to be stable. Ionization was also found to enhance the formation of cluster species. (C) 1999 Elsevier Science B.V. All rights reserved.