Energy bands and mass enhancement in yttrium

The electronic structure of Y has been calculated with the linear Muffin-Tin-Orbital method including the relativistic effects. The energy eigenvalues were determined at 392 points in the irreducible zone, with a local-density potential. The energy bands were also calculated with a non-self-consistent potential constructed from a superposition of atomic charge densities. These potentials gave rise to significantly different s-band positions, but the separation between the p- and d-bands was almost identical in the two cases. Since the state-density at the Fermi level has an s-component of only about 1% the Fermi surfaces in the two cases are very similar. The comparison between the measured and calculated Fermi-surface areas and masses is tabulated. It was concluded that the discrepancies were due to the calculated p-band lying too high relative to the d-band; when this was lowered artificially better agreement was obtained. The overall mass enhancement of the electrons at the Fermi surface in Y is considerably larger than for most other hcp transition metals. This may be due to magnetic effects. (U.K.)