INST HIGH ENERGY PHYS,BEIJING SYNCHROTON RADIAT FACIL,BEIJING 100039,PEOPLES R CHINA
; BRUNEL UNIV,DEPT PHYS,UXBRIDGE UB8 3BH,MIDDX,ENGLAND
; SERC,DARESBURY LAB,WARRINGTON WA4 4AD,CHESHIRE,ENGLAND
Au-substituted Al-Cu-Fe icosahedral phases, Al62Cu25.5-xAuxFe12.5 (x less than or equal to 7) were prepared by melt spinning. EDS data showed that Cu as well as Al atoms are effectively substituted for with Au. The hypercubic lattice parameter of as-quenched samples slowly increases with x, while phonon-and phason-type disorders are not affected by Au substitution. Experimental structure factors for 'sum' lines were used to derive an average radius of the atomic hypersurfaces. Comparison of experimental versus calculated ratios of structure factors for different models yielded information about the Au distribution over the icosahedral sites. It was inferred that a fraction of the gold shapes its Al surrounding in a AuAl2-type configuration. Evidence was found for d-sp hybridization of Au-Al bonds, on the basis of the 'white-line' area at the Au L-3 absorption edge.