TiO₂ nano-clusters adsorbed on surfaces: A density-functional-theoretic study

We performed density-functional-theoretical calculations to investigate the adsorption of two stable nano-clusters corresponding to (TiO₂)_N with N= 3 and 5 supported on three different type of substrates: graphene, silver and gold. For each of these surfaces we consider three textures: pristine, with a single vacancy and with a Co atom as impurity. In the case of the defects (vacancy or impurity) they act as possible anchors for the adsorption of the cluster. The proposed particles present flat configurations in their respective free standing putative ground states, so they can accommodate themselves as parallel, perpendicular or inclined with respect to the surface producing different isomers: only the four lowest energy isomers for each particle (N = 3 or 5), each surface and each texture are reported and analyzed. Density Functional Theory calculations by means of the SIESTA package are done in a thorough way covering a large number of the possible configurations. Reported parameters are: adsorption energy, assisted binding energy (binding energy in the presence of the substrate), and the main different interatomic distances presented in the adsorption. A comparison with some previous theoretical results on related systems is done. Possible extensions of this work are commented.