Statistical thermodynamics of highly defective compounds

A method aimed at extracting information, essentially formation and interaction energies of defects, from partial molar quantities of largely nonstoichiometric compounds, has been developed. Two quite different examples, a partially ionic compound, cerium dioxide, and a semimetal, titanium monoxide, have been considered. The method consists of calculating to a good approximation the partition function of a small system containing some tens of atoms, immersed in a large reservoir and representing the compound. Formation and interaction energies of defects are parameters adjusted from experimental data. The treatment of both short- and long-range interactions is discussed