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 A173Co16Ni11 quasicrystalline films are presented. Layers were grown by solid state reaction of a multilayer 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 Å 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 element can also be applied to other quasicrystalline structures modelled by using a cut-and-projection method from a high-dimensional space. The average neighbourhood of Ni and Co atoms was found to be equal within a radius of 3 Å. Sites of transition metals should be occupied statistically by Ni and Co