Theory of Alkali Halide Solid Solutions

Dilute solid solutions of the system NaCl-NaBr are considered. The displacements of the nearest, next-nearest, and third-nearest neighbors are dealt with microscopically and the rest of the medium is regarded as a continuous elastic medium. Heats of solution and changes in lattice constants are calculated and compared with experiment. Because of the distortion of the crystal around the impurity, appreciable field-gradients appear at the nuclei in the neighborhood of the impurity. These field gradients are calculated and compared with some available experimental results obtained from nuclear magnetic resonance studies of these solid solutions.