In the calculation of migration and formation volumes, various relations between defect parameters and elastic constants have been proposed. Recent experiments by Samara on ionic crystals agree with the view that migration and formation parameters are connected to the bulk modulus rather than to another combination of elastic constants. This has been previously proposed by the authors on intuitive grounds; the anharmonicity was found to be a pertinent factor. In the Appendixes the proposal receives a well-founded proof for the migration and formation process.

• Received 16 June 1980

DOI:https://doi.org/10.1103/PhysRevB.24.904