Dynamics of long-wavelength phason fluctuations in the i-Al–Pd–Mn quasicrystal

“…Then in situ studies were carried out at high temperature and time-dependent phason fluctuations were observed above 873 K (Francoual et al, 2003). In Francoual et al (2006), the dynamics of the phason fluctuations was shown to be of a diffusive type, with a diffusion constant D ? like in equation (23) Charge-density waves (CDW) are observed from Bragg peaks in metals.…”

Section: Fluctuations In Metalsmentioning

confidence: 99%

Diffraction with a coherent X-ray beam: dynamics and imaging

Livet

2007

Acta Cryst Sect A

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Methods for carrying out coherent X‐ray scattering experiments are reviewed. The brilliance of the available synchrotron sources, the characteristics of the existing optics, the various ways of obtaining a beam of controlled coherence properties and the detectors used are summarized. Applications in the study of the dynamics of speckle patterns are described. In the case of soft condensed matter, the movement of inclusions like fillers in polymers or colloidal particles can be observed and these can reflect polymer or liquid‐crystal fluctuations. In hard condensed‐matter problems, like phase transitions, charge‐density waves or phasons in quasicrystals, the study of speckle fluctuations provides new time‐resolved methods. In the domain of lensless imaging, the coherent beam gives the modulus of the sample Fourier transform. If oversampling conditions are fulfilled, the phase can be obtained and the image in the direct space can be reconstructed. The forthcoming improvements of all these techniques are discussed.

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“…The characteristic time is smaller for longer wavevector and is of the order of 20 to 100 seconds for the wavevector considered. 18,19 The characteristic times go like 1/q 2 as expected for a diffusive mode. The process is energy activated with an activation energy equal to about 3 eV.…”

Section: Marc De Boissieumentioning

confidence: 91%

Phonons, phasons and atomic dynamics in quasicrystals

Boissieu

2012

Chem. Soc. Rev.

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We review some of the results obtained for the study of phason, phonon and atomic dynamics in quasicrystals. In the framework of the hydrodynamic theory long-wavelength phason modes are characteristic of quasicrystal and are diffusive modes. Quenched-in phason mode gives rise to a characteristic diffuse scattering, observed in all the 'stable' icosahedral quasicrystals studied so far. In the AlPdMn icosahedral phase, above T = 500 °C, equilibrium phason modes are shown to be diffusive modes in agreement with the hydrodynamic theory. The lattice dynamics has been studied by inelastic neutron or X-ray scattering. Well defined acoustic modes are only observed for wavevectors smaller than 0.3 Å(-1). Above this value, the mode rapidly broadens as a result of mixing with higher energy modes. We show that the results can be interpreted using the concept of pseudo-Brillouin zone boundary and can qualitatively explain the differences observed in the response function of the ZnSc 1/1 approximant and its quasicrystalline counterpart. The observations are qualitatively and quantitatively reproduced using oscillating pair potentials, which open the route for a detailed analysis of the lattice dynamics at the atomic scale. An exceptional dynamical flexibility is also evidenced in the 1/1 approximant. A brief discussion on the implication of those results on the stabilizing mechanisms of quasicrystals is given at the end of the paper.

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Dynamics of long-wavelength phason fluctuations in the i-Al–Pd–Mn quasicrystal

Cited by 31 publications

References 14 publications

Stability of aperiodic crystals

Stability of aperiodic crystals

Diffraction with a coherent X-ray beam: dynamics and imaging

Phonons, phasons and atomic dynamics in quasicrystals

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