The enthalpy $h_m$ for the migration of a cation vacancy in alkali halides has been calculated from macroscopic parameters such as the bulk modulus. By connecting the mean-square phonon frequency to the bulk modulus and by using the Debye approximation of a solid and Lindemann's equation we conclude that the proposed method for calculating $h_m$ actually shows a correlation of $h_m$ to the melting point; this correlation has been experimentally observed.

• Received 17 January 1977

DOI:https://doi.org/10.1103/PhysRevB.15.5994