Contribution of Strain to Nuclear Quadrupole Interactions in Dilute Alloys of Copper

Abstract

The hypothesis that electric field gradients due to elastic strains (size effect) about the solute atom in dilute alloys of a cubic metal form an important part of the total field gradient at the solvent nuclei is developed quantitatively. Results have been applied to a consideration of recent nuclear magnetic resonance experiments by Rowland on dilute copper alloys which were interpreted by him and by Kohn and Vosko in terms of the spatially oscillating charge due to conduction electron redistribution (valence effect.) The good agreement with theory they obtained is further improved to a significant degree by the simultaneous consideration of both size effect and valence effect. It is found that the field gradients due to size effect are in fact comparable in magnitude to those due to the valence effect. The magnitude of the size effect is described by a single parameter characteristic of the solvent. It is found that the value of this parameter obtained for copper metal is larger than that indicated by recent experiments by Faulkner and by by Averbuch, de Bergevin, and M\"uller-Warmuth, and possible causes of this disagreement are discussed.