Anomalous-X-ray scattering associated with short-range order in an Al70Ni15Co15 decagonal quasicrystal

The diffuse scattering around Bragg reflections was observed in a single decagonal quasicrystal of Al70Ni15Co15 using anomalous-X-ray scattering. The intensities of diffuse scattering vary with the three incident X-ray wavelengths, near the Co K-edge and the Ni K-edge and between them. The contrast of diffuse scattering shows the existence of atomic short-range order (SRO) between Ni and Co. The distributions of diffuse scattering are anisotropically modulated and the diffuse shapes vary from one reciprocal lattice point to another. In quasicrystals, anisotropic diffuse shapes derive from phason strain. It is concluded that both SRO and phason strains exist in Al70Ni15Co15. In addition, as the first neighbor of Ni, Ni is preferred to Co statistically, since SRO intensities appear about zone-centers, i.e. there is local clustering of these species.