A method is proposed for estimating the free energy of cation vacancy migration in alkali halides with NaCl structure from macroscopic parameters. It is based on the calculation of the electrical and the dilatation work during the migration of the cation. The dilatation work can be calculated from the elastic constants and the migration volume corresponding to free-cation motion. By considering anharmonic effects the free energy is calculated as function of temperature. In the high-temperature region the temperature-independent part of the migration free energy and its temperature derivative give values which agree with the published values of the migration enthalpy and entropy.

• Received 18 August 1975

DOI:https://doi.org/10.1103/PhysRevB.15.2348