The purpose of this study is the assessment of the adsorbing properties of the clustered phase of bulk materials and tin oxide has been chosen as a relevant example. Therefore clusters with the rutile lattice and a model size up to approximately 100 atoms have been considered and the adsorbed system is generated by depositing a CO molecule onto the grain surface. The results indicate the formation of a stable complex formed by the cluster, with an essentially unchanged shape, and by the deposited molecule which has a small displacement and rotation with respect to the incidence conditions. An extensive testing on the parameters needed by the DFT formulation indicates fluctuations of either the structural parameters or the structure of the allowed energy levels. There are three sources for these effects, i.e. the evaluation of the spin distribution, the choice of the correlation potential and the limited size of the …