Calculation of the entropy of defect processes in ionic solids

Abstract

Rough estimates of the entropy of formation of defects have long been available. An example for Schottky defects was given by Mott and Gurney in their book published in 1948. Accurate calculations of the entropy, however, require the evaluation of the defect-lattice phonon spectrum. This gives an entropy at constant volume. The corrections to obtain entropies at constant pressure are large and frequently change the sign of the defect parameter. We discuss methods of calculating entropies of formation and migration. A brief discussion of the meaning of the parameters obtained (particularly for migration) is also given.