Disordered quasicrystals: diffuse scattering in decagonal Al–Ni–Fe

High-resolution synchrotron data of near-Bragg diffuse scattering from decagonal Al_71.5Ni_23.5Fe₅ quasicrystals were recorded. A dominant phasonic origin is ruled out because of the absence of a significant G_⊥ dependence. An analysis solely in the frame of thermal diffuse scattering (TDS) theory (phonon scattering) showed a good match between experimental and calculated data in the quasiperiodic layers, but with an improbable ratio of elastic constants, c₆₆/c₁₁ = 4.0. In situ high-temperature measurements up to 1000 K revealed an increase of the intensity distribution perpendicular to the scattering vector G. Huang diffuse scattering (HDS) arising from quenched local defects has a general appearance that qualitatively reproduces the observed symmetry and anisotropy. An interpretation based on both TDS and HDS contributions is given.