Anisotropic phasonic diffuse scattering from decagonal quasicrystals

In spite of its isotropic elastic (phonon) properties, anisotropic diffuse scattering is observed in icosahedral quasicrystals and interpreted as a consequence of softening of a particular mode of phasons near hydrodynamic instability. In a decagonal case, the phason elastic energy is isotropic and no anisotropic phason disorder is expected. We show that, nevertheless, the anisotropic diffused scattering from the decagonal quasicrystals is expected through the phason–phonon coupling. We calculate a line shape of the diffuse scattering based on the elasticity theory for 10/mmm and 10m2 symmetries. Physical meanings of such diffuse scattering are discussed in contrast to Huang scattering.