SOFT PHASON MODES INDUCING RHOMBOHEDRAL-ICOSAHEDRAL TRANSFORMATION

Phason modes responsible for the newly discovered rhombohedral-icosahedral structure transformation in Al-Cu-Fe alloy are discussed. By locking the phason strains to a special configuration giving the Ih->D3d symmetry change, we obtain a periodic structure with a prolate rhombohedral unit cell, which is a doubled version of the t3 prolate rhombohedron obtained by the elementary face-matching rule. It is shown that the diffraction pattern for this periodic lattice is consistent with the diffuse scattering line shapes around the structural ‘transition’ temperature. © 1990 Taylor & Francis Group, LLC.