Research Papers in Physics and Astronomy


Date of this Version



Published in Physical Review Volume 5, Number 8, 15 August 1972. Copyright 1972. Used by permission.


The method of lattice statics and the deformation-dipole model have been applied to Schottky defects in ionic crystals in approximations higher than zero order. For an isolated vacancy, all host-lattice-ion potential energy functions for short-ranged repulsive and Coulomb-defect forces were expanded to terms quadratic in the displacements and dipole moments, and the resulting forces were allowed to act on the first and/or second neighbors to the vacancy. The zero-order Coulomb force was allowed to act on the remainder of the host-lattice ions past first and/or second neighbors. The vacancy and Schottky-pair-formation energies in the 12 Na, K, Rb halides have been calculated. A comparison is made between the zero-order approximation and the one considered here. Fairly good agreement is obtained between our calculated values and the experimental values for the Schottky-pair-formation energies if the polarizations around the defect are properly treated with respect to deformation dipoles.

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