THE KNIGHT SHIFT IN LEAD TELLURIDE VIA RELATIVISTIC APW FUNCTIONS.
Abstract
The 82Pb207 nucleus was used, via the measured Knight Shift, to test the accuracy of the relativistic APW calculations for the energy bands of PbTe. Possible Knight Shift contributions other than the contact type are considered and shown to be negligible; the confusion between the Knight Shift and the chemical shift is discussed. The standard formula for the contact Knight Shift in a semiconductor is examined, and is found to be based on the assumption, for a powder specimen, of an isotropic g-factor. It is shown that the large anisotropy of the g-factor in PbTe leads to a correction factor of 4. From the relativistic APW results a value is obtained for the s-character, and also a value for the ionicity. This latter is used, together with relativistic and finite nucleus corrections important for hyperfine interactions involving heavy nuclei, to obtain a value for the hyperfine constant, using the Goudsmit-Fermi-Segre formula. When the calculated s-character, hyperfine constant and anisotropy correction factor are employed with the average experimental value of the g-factor, a Knight Shift value is obtained which is about half the experimental value. Taking into consideration the lack of self-consistency of the relativistic APW calculations, and allowing for the possibility that the experimental values for the g-factor are too small, the APW results are felt to provide a good basis for the explanation of the Knight Shift. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 22, 1966
- Accession Number
- AD0642519
Entities
People
- Paul T. Bailey
Organizations
- Massachusetts Institute of Technology