Short-range order in a thin film of decagonal Al-Co-Ni quasicrystal: calculated from a structure model and measured with EXAFS

Extended X-ray Absorption Fine Structure (EXAFS) measurements performed at the Co and Ni K absorption edges of thin decagonal Al73Co16Ni11 quasicrysta lline films are presented. Layers were grown by solid state reaction of a m ultilayer stack of elemental metals. Experimental data of short range order is compared to that calculated from a modified Li-Steurer structure model. To fit the measured EXAFS function, the neighbourhood of transition metals cobalt and nickel up to 3 Angstrom was calculated from this model. Overlap of hyperatoms in the perpendicular space has been taken into account. The algorithm for the calculation of the average neighbourhood of a given eleme nt can also be applied to other quasicrystalline structures modelled by usi ng a cut-and-projection method from a high-dimensional space. The average n eighbourhood of Ni and Co atoms was found to be equal within a radius of 3 Angstrom. Sites of transition metals should be occupied statistically by Ni and Co. (C) 1999 Elsevier Science S.A. All rights reserved.