Stability of grains of metallic oxides with a rutile structure. A quantum mechanical study

The focus of this study is on the stability of grains of metallic oxides, i.e., TiO2 and SnO2, with a rutile lattice. To this purpose, the grain binding and fragmentation energies have been evaluated quantum mechanically at semi-empirical level using the extended Debye-Hueckel approximation. The grain size and shape are variable and the shapes have been chosen to reproduce, with some approximation, realistic structures found in nanocrystalline technologies. The results show noticeable differences with respects to the known behavior of homonuclear structures. In fact, the grain stability generally increases with the cluster size, as in the homonuclear case. However, its primary dependence is on the oxygen content, rather than on the grain size. On the contrary, the density of states has a critical dependence on the cluster size and is almost equal for the two materials.