J. Phys. Colloques
Volume 47, Numéro C3, Juillet 1986International Workshop on Aperiodic Crystals
|Page(s)||C3-259 - C3-270|
J. Phys. Colloques 47 (1986) C3-259-C3-270
DIFFRACTION FROM QUASICRYSTALS : ORIENTATIONAL ORDER, ATOMIC STRUCTURE, AND ELASTICITYM.V. JARIC1, 2
1 Department of Physics, Harvard University, Cambridge, MA 02138, U.S.A.
2 On leave from Department of Physics, North Dakota State University. Fargo. ND 58105, U.S.A.
Work related to several properties of the structure factor of quasicrystals is summarized. It is shown that bond-orientational order induces icosahedral quasicrystalline order. A phase with pure icosahedral orientational order is also possible and it may lead to diffraction patterns similar to the ones found experimentally. The geometric structure factors for the two commonly used methods of modeling quasicrystal structures are also derived. It is shown that decoration of the quasicrystalline tiles generally lifts the nodes of the intrinsic structure factor. The effect of thermal fluctuations on the structure factor of quasicrystals is examined. Phonon and phason elastic constants are calculated to obtain the Debye-Waller factor and the diffuse thermal broadening. It is suggested that the diffuse broadening (thermal, or due to quenched phasons) might explain the observed widths of the diffraction peaks of icosahedral quasicrystals as well as the appearance of the sheets of diffuse intensity observed in the decagonal quasicrystals.