The purpose of this study is to get insight into the instability which is observed, under operative conditions, in the SnO2 nanocrystalline materials. To this purpose, the binding and fragmentation energies of SnO2 crystalline grains have been evaluated quantum mechanically at semi-empirical level using the extended Debye-Huckel approximation (EHA). The grain structure 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. It has been found that the interplay of the grain composition and shape, rather than its size, has a primary role on the grain stability. These features represent a central difference with respect to the known properties of pure clusters whose energetics is uniquely dictated by the size. (C) 2003 Elsevier B.V. All rights reserved.