NEUTRON-SCATTERING STRUCTURAL STUDY OF ALCUFE QUASI-CRYSTALS USING DOUBLE ISOTOPIC-SUBSTITUTION

Neutron diffraction data with double isotopic substitution using two isotopes each of Fe and Cu has been obtained on six samples of quasicrystalline AlCuFe with a 6D face-centered icosahedral symmetry. Calculations of heteroatomic and homoatomic pair correlation functions for this structure have been made. We find that there is a localized position of copper on a 6D body center site which gives a clear but still qualitative picture of the structure with iron, copper, and aluminum chemically ordered and occupying successive concentric 'shells' in the large atom surfaces centered at the two major atomic positions, n1 = [0, 0, 0, 0, 0, 0] and n2 = [ 1, 0, 0, 0, 0, 0], (indexed with respect to a primitive unit cell) in this 6D NaCl type structure. There is an indication that some of the aluminum is mixed with the iron (or is encapsulated in a small volume inside an iron surface).