ISOMER-SHIFTS AND ELECTRIC-FIELD GRADIENTS IN Y(FE1-XALX)2

The electronic structure of the intermetallic compound Y(Fe1-xAlx)2, a cubic Laves phase, is investigated by the full potential LAPW method. Spin-polarized calculations for YFe2 and two ordered structures with x = 0.25 and 0.75 are performed for different volumes. These calculations yield charge densities at the Fe nucleus and lead to isomer shifts (IS) which reproduce the trends of the available experimental data. The increase in volume and the Al substitution contribute about equally to the variation of the IS in this system. The electric field gradient (EFG) is calculated on a first principles basis for all cases studied, but comparison with experiment is made difficult for various reasons.