P. A. Heiney, P. A. Bancel, P. M. Horn, J. L. Jordan, S. LaPlaca, J. Angilello, and F. W. Gayle, Science 238, 660-663 (1987).
Faceted dendrites of icosahedral Al6Li3Cu have been studied by high-resolution x-ray scattering. The samples display long-range icosahedral symmetry both in their diffraction patterns and in their macroscopic morphology. Despite the appearance of well-defined facets, the samples have a high degree of atomic disorder. The Bragg peaks have symmetry-dependent shapes and widths that scale linearly with G_perp (phason momentum). The peak widths are surprisingly similar to those found in icosahedral Al-Mn-Si alloys both in their absolute magnitudes and their dependence on G_perp. The origin of these features in models for the icosahedral phase is discussed.
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