Atomic (phason) hopping in perfect icosahedral quasicrystalsAl70.3Pd21.4

Abstract

We report neutron-scattering results on atomic hopping in quasicrystals ͑QC͒ in the system Al-Pd-Mn. Two distinct atomic jump times have been observed and studied as a function of temperature. The unusual temperature behavior reported previously for 3.9 Å jumps in Al-Cu-Fe ͑and interpreted as evidence for assisted hopping͒ is also found here, such that it seems to be universal. We provide a full discussion of all previous quasi-elastic-scattering results in QC, and show that their most reasonable interpretation is in terms of atomic hopping ͑phason dynamics͒. The relation of these data to theoretical predictions of fast diffusion and depinning transitions in the phason dynamics is examined.

Theory of Phasons in Aperiodic Crystals

“…The three types of 'phason' have been seen experimentally. Phason jumps have been seen by time-of-flight neutron scattering [1] and time resolved electron microscopy [2]. Phason strain can often be seen in HREM pictures as discontinuities in rows of particles.…”

Thermal phason fluctuation in an Al–Cu–Co decagonal quasicrystal

“…, and as jogs in atomic rows in high-resolution transmission electron microscopy (HRTEM) images [4,7] and in scanning tunneling microscopy (STM) images [8]. On the other hand, dynamical phasons, or thermally-induced phason flips, have been investigated by neutron scattering [9][10][11][12], by M€ ossbauer spectroscopy [13], by NMR [14,15] and by heat capacity measurements [16,17]. Long wavelength phason fluctuations have been investigated by X-ray and neutron diffuse scattering measurements [18][19][20].…”

A new phasing method based on the principle of minimum charge

“…It should be emphasized that all these artifacts are not speci®c to the phasing method and will exist in any reconstructed quasicrystalline density map. They should not be confused with the phason disorder in real quasicrystals (Lyonnard et al, 1996;de Arau  jo et al, 1996;de Boissieu et al, 1995), which manifests itself in the occurrence of true partially occupied sites at the same positions.…”