Densities, Lattice Parameters and Defect Chemistry of Pure Non-stoichiometric Compounds

General relations are derived between the quantities describing the defect chemistry of pure, non-stoichiometric compounds and the experimental values of lattice parameters and densities of these materials. These relations show how to analyse the experimental data without the need for arbitrary assumptions about the defect situation. The theory is applied to published data of non-stoichiometric TiO, TiS(2), Ti(2)S(3), and Bi(2)Te(3). The models assumed in the literature, in order to interpret the experimental data, are shown to be only the most simple among a series of possible defect situations which are consistent with the data.