A quantum mechanical study of the stability of SnO2 nanocrystalline grains

The purpose of this study is to gain insight into the instability which is observed, under operative conditions, in SnO2 nanocrystalline materials. For this purpose, the binding and fragmentation energies of SnO2 crystalline grains have been evaluated quantum-mechanically at a semiempirical level using the extended Debye-Hückel approximation. The inner structure of the grains is assumed to be an unreconstructed rutile lattice, as in the parent solid. The grain size and shape are variable and a parametric search has been carried out on both quantities. In broad terms the grains show a bulk-like behaviour, as their characteristic energies are approximately independent of their size and shape. However, the increases in the grain size and in the oxygen content may increase the grain stability. These features are discussed in the light of the properties of small clusters formed by tin and oxygen.