Anomalous Debye–Waller Factor Associated with an Order–Disorder Transformation in an Al₇₂Ni₂₀Co₈Decagonal Quasicrystal

Abstract

An order–disorder transformation in a single decagonal quasicrystal of Al 72 Ni 20 Co 8 is studied in detail. In X-ray diffraction, the anomalous attenuation of intensities of Bragg reflections was found around the transformation temperature, T c . The intensity attenuation at high temperature is explained by the anomalous Debye–Waller factor in thermal lattice dynamics. In particular, the intensity ratio above T c and below T c depends on | G || | 2 values. In addition, the intensity ratio between room temperature and high temperature shows | G ⊥ | 2 dependence. The results correspond to the in situ observation of a local vibrational anomaly related to an atomic flip by electron microscopy [Abe et al. : Nature 421 (2003) 347]. By X-ray diffraction, dynamic fluctuations as observed in electron microscopy are also realized even on a macroscopic scale at high temperature.