Phonon- and phason-type spherical inclusions in icosahedral quasicrystals

• Published in: Journal of physics. Condensed matter 2003-06, Vol.15 (24), p.L363-L370
• Main Authors: Wang, Jianbo, Mancini, L, Wang, Renhui, Gastaldi, J
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Lattice dynamics; Physics; Vibrational states in disordered systems
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/15/24/102

Analytical expressions are derived as a first-order approximation for the elastic displacement fields, including both phonon- and phason-type components, induced by spherical inclusions in icosahedral quasicrystals (IQCs). The phonon-type component obtained is the same as that for a spherical inclusion in conventional elastically isotropic crystals, while the expression for the phasontype displacement, which decreases with increasing distance r to the sphere centre as r-1, is derived for the first time. Three concrete cases are discussed. The phonon part of the analytical expressions has been used to simulate the black-white double-lobe contrasts in the x-ray topograph (XRT) images of the strain field around the pores in the AlPdMn IQCs. The analytical expression for the phason-type displacement is used to simulate the XRT images of the strain field around spherical inclusions having isomorphic structures. The striking resemblance between experimental and simulated images suggests that such inclusions are surrounded by antiphase boundaries with a phason-type displacement vector, being particular structural defects in IQCs.