Inelastic neutron scattering study of the dynamics of the AlNiCo decagonal phase

Dugain, F.; Boissieu, M. de; Shibata, Kaoru; Currat, R.; Sato, Toyoto; Kortan, A. R.; Suck, J.-B.; Hradil, K.; Frey, Friedrich; Tsai, A. P.

doi:10.1007/s100510050640

Cited by 33 publications

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“…In the range of 0.3 to 0.6 Å À1 one observes a rapid broadening of the observed excitation, whereas the dispersion relation bends over. 48,[50][51][52] This generally corresponds to the crossing of the acoustic branch with a dispersionless broad optical excitation or to a pseudo-gap opening as in the case of the i-Zn-Mg-Sc quasicrystal shown in Fig. 4.…”

Section: Phonons In Quasicrystalsmentioning

confidence: 96%

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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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Section: Phonons In Quasicrystalsmentioning

confidence: 96%

“…51 For all phases there is a well defined acoustic mode for wavevectors smaller than 0.3 Å À1 with a width limited by the instrumental resolution and a linear dispersion. In the range of 0.3 to 0.6 Å À1 one observes a rapid broadening of the observed excitation, whereas the dispersion relation bends over.…”

Section: Phonons In Quasicrystalsmentioning

confidence: 99%

Phonons, phasons and atomic dynamics in quasicrystals

Boissieu

2012

Chem. Soc. Rev.

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“…6,7 However, it is only recently that there has been increasing evidence for nonacoustic low-energy states that show up in the phonon DOS ͑Refs. 15 and 28, in excess heat capacity 11 or in an atypical low-temperature variation of the sound velocity.…”

Section: F Nonacoustic Excitations At Low Energiesmentioning

confidence: 99%

Atomic dynamics in Al-rich Al-Co alloys near the composition of the decagonal quasicrystal

2001

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We used realistic Al-Co pair potentials ͓R. Phillips, J. Zou, A. E. Carlsson, and M. Widom, Phys. Rev. B 49, 9322 ͑1994͒; J. A. Moriarity and M. Widom, ibid. 56, 7905 ͑1997͔͒ to study the atomic dynamics of Al 1Ϫx TM x crystalline structures with the fractional content x of the transition metal ͑TM͒ atom xՇ0.3. Our list comprises rather simple structures of Al 3 Ni and Al 5 Co 2 alloys, complex structures related to the decagonal quasicrystal (Al 9 Co 2 Ni, O-Al 13 Co 4 ), and a model of the crystalline approximant of the decagonal quasicrystal d-AlNiCo. Within the harmonic approximation, we assess the impact of the structural complexity on the phonon density of states, sound velocity, Debye-Waller factor, and the character of the phonon states at low energies. In complex structures related to the decagonal quasicrystal, a significant fraction of low-energy vibrations have nonacoustic, strongly localized character. In a molecular-dynamics annealing of the decagonal approximant model performed at elevated temperature, a fraction of aluminum atoms display signs of diffusive motion, while the equilibrium positions of the cobalt atoms do not change.

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“…To measure the largest signal one should measure S(Q,) at high momentum transfer and close to a strong Bragg peak. Neutron scattering investigations were performed for different icosahedral [12][13][14][15] and decagonal 16 structures and it turned out that in spite of the fact that, structurally, decagonal and icosahedral QCs are rather different, and that their physical properties ͑e.g., elastic moduli͒ might be also very different, they exhibit many common vibrational features. The purpose of our paper is to propose a simple phenomenological model to try to obtain as much theoretical information concerning vibrations in QCs as is possible on a phenomenological level without specific microscopic treatment.…”

Section: Introductionmentioning

confidence: 99%

Sound-mode broadening in quasicrystals: A simple phenomenological model

et al. 2004

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We propose a simple phenomenological model to analyze vibrational characteristics of quasicrystals ͑QCs͒. The interpretation of the obtained recently data is based on the existence of almost dispersionless optical modes most probably related to the specific clusters which constitute the characteristic building blocks of any QC structure. We generalize to QCs the well-known Akhiezer mechanism ͑responsible for the absorption of sound even in an ideal crystal͒, which in our case is related to a ''long wave'' disturbance of the quasicrystalline optical modes by the propagating sound modes. At higher wave vectors strong hybridization of acoustic and optical modes takes place, and it leads to a more steep broadening dependence on wave vectors, and besides the excitation can no longer be described as a single acoustic mode with a well defined wave vector. We show that the observed sound-mode attenuation behavior can be consistently described by these scenarios without invoking additional mechanisms.

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Inelastic neutron scattering study of the dynamics of the AlNiCo decagonal phase

Cited by 33 publications

References 0 publications

Phonons, phasons and atomic dynamics in quasicrystals

Phonons, phasons and atomic dynamics in quasicrystals

Atomic dynamics in Al-rich Al-Co alloys near the composition of the decagonal quasicrystal

Sound-mode broadening in quasicrystals: A simple phenomenological model

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