Molecular geometries and relative stabilities of titanium oxide and gold-titanium oxide clusters

Abstract Titanium oxide and gold-titanium oxide clusters of stoichiometry M x O y (M x  = Ti 3 , Ti 4 & AuTi 3 ; y  = 0 − (2 x  + 2)) have been investigated using density functional theory. Geometries of determined global energy minimum structures are reported and other isomers predicted up to 0.5 eV higher in energy. The Ti 3 O n geometries build upon a triangular Ti 3 motif, while Ti 4 O n stoichiometries template upon a pseudo-tetrahedral Ti 4 structure. Addition of a gold atom to the Ti 3 O n series does not significantly alter the cluster geometry, with the gold atom preferentially binding to titanium atoms over oxygen atoms. Adiabatic ionization energies, electron affinities and HOMO/LUMO energies increase in magnitude with increasing oxygenation. The HOMO-LUMO energy gaps reach the bulk anatase band gap energy at stoichiometry (Au)Ti m O 2 m −1 , and increase above this upon further oxygen addition. The most stable structural moieties are found to be a cage-like, C 3v symmetric Ti 4 O 6/7 geometry and a Ti 3 O 6 structure with an η 3 -bound oxygen atom.