THE GAP IN YH3 AND ITS LATTICE STRUCTURE

A systematic study has been carried out on the electronic structure of YH3. The attention was focused on the conditions for finding an energy gap, in accordance, with experimental evidence. The calculations are made with a localized spherical wave (LSW) program, which is based on a first-principles light-binding version of the augmented spherical wave method. No gap was found for the FCC structure in spite of the use of a great variety of model parameters. However, a non-self-consistent run of the program for this structure reproduced the gap of 2 eV found by Switendick. No gap was found for several versions of the HCP structure either, including the rather complicated HoD3 structure. The separation of the bands a-round the Fermi level, as found for the LaF3 structure, could explain the light transmission measurements.