Trends in the electric quadrupole fields at dilute impurity sites in transition-metal-transition-metal alloys

• Published in: Physical review. B, Condensed matter Condensed matter, 1984-11, Vol.30 (9), p.5209-5219
• Main Authors: WATSON, R. E, STERNHEIMER, R. M
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystal and ligand fields; Defects and impurities in crystals; microstructure; Electron states; Exact sciences and technology; Level splitting and interactions; Materials science; Metals, semimetals and alloys; Physics; Specific materials; Structure of solids and liquids; crystallography
• ISSN: 0163-1829; 1095-3795
• DOI: 10.1103/PhysRevB.30.5209

The available electric-field-gradient data at transition-metal impurity sites and at host sites in transition-metal hosts has been inspected for indications of trends in alloying behavior. The raw data separate the gradients into two groups, depending on whether the host metal has over, or under, half-filled d bands. The normalized results suggest that the observed gradients, by their very magnitude, must be largely intra-atomic in origin. Granted this, and assuming that it is the d electrons which are primarily responsible, while there is scatter in the data, the gradients at host and impurity sites, in the under-half-filled d-shell hosts, show little chemical variation within either differing impurity or differing host. The normalized results for the over-half-filled d-shell hosts, on the other hand, appear to show a chemical trend which is also to be seen in the enthalpies of formation of the more concentrated alloys. The renormalized-atom scheme was employed to obtain the contributions from d- and valence p-electron charge. It is not widely appreciated as to how important p-electron bonding can be to the gradients. Sternheimer antishielding factors, gamma sub infinity , were also required. Lacking values for some of the elements of concern, a simple scaling with the size of the atom was introduced. This was inferred from a number of sequences of ions and then applied to predictions for the 5d elements. The scaling worked well and should also do so in other cases. 34 ref.--AA