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Phason diffuse scattering in the icosahedral quasicrystalline phases Zn-X-Sc, X = Co, Ag, Mg

Sonia M. P. Francoual - National High Magnetic FieldLaboratory, Los Alamos, New Mexico, 87545, USA


Sonia M. P. Francoual(1)(*), Marc de Boissieu(2), Roland Currat(3), Shiro Kashimoto(4), Tsutomu Ishimasa(4)

 

(1) National High Magnetic FieldLaboratory, sfranco@lanl.gov, Los Alamos, New Mexico, 87545, USA

(2) Laboratoire de Thermodynamique et Physico-ChimieMetallurgiques, St Martin d’Heres, France,

(3) Institut Laue Langevin, Grenoble, France

(4) Graduate School of Engineering,Hokkaido University, Sapporo, Japon

 

According to the hydrodynamic theory of quasicrystalline materials, the long range quasiperiodic order yields in quasicrystals new long-wavelength modes, the phason modes, in addition to the acoustic phonons. Phason excitations are diffusive and associated with internal atomic rearrangements the dynamics of which is expected to lead to a distinctive diffuse scattering signal around Bragg peaks in reciprocal space. Up to now, experimental demonstration for the existence of phason diffuse scattering was given in the enlightening single case of the Al-Pd-Mn Mackay-type icosahedral (i-) phase from which the phason elastic constants were extracted and the thermal activation unvealed. In the present communication, we report on X-ray synchrotron investigations of the diffuse scattering in the i-Zn-X-Sc (X = Mg, Ag, Co) phases and the Zn-Sc 1/1 periodic approximant bringing evidence for the presence of long wavelength phasons in this new class of icosahedral quasicrystalline phases and ruling it out in the 1/1 approximant structure.

 

(*) email : sfranco@lanl.gov

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