Atomic dynamics of the i-ScZnMg and its 1/1 approximant phase: experiment and simulation

Marek Mihalkovic (1) , Sonia Francoual (2, 3) , Kaoru Shibata , Marc de Boissieu (2) , a Q.R. Baron (4) , Yvan Sidis (5) , Tsutomu Ishimasa (6) , Thomas Lograsso (7) , L.P. Regnault (8) , Franz Gähler (9) , T Tsutsui (4) , Bernard Hennion (5) , P Bastie (10) , Taku Sato (11) , Hiroyuki Takakura (12) , R. Currat (13) , a Peter Tsai (14)

1 Institute of Physics
2 SIMaP - Science et Ingénierie des Matériaux et Procédés
3 ILL
4 JASRI - Japan Synchrotron Radiation Research Institute [Hyogo]
5 LLB - UMR 12 - Laboratoire Léon Brillouin
6 Division of Applied Physics
7 Ames Laboratory [Ames, USA]
8 CEA
9 Institut für Theoretische und Angewandte Physik
10 UJF
11 Neutron Science Laboratory
12 Applied Physics
13 ILL
14 NIMS - National Institute for Materials Science

Quasicrystals are long range ordered materials which lack translational invariance so that the study of their physical properties remains a challenging problem. In order to study the respective influence of the local order and of the long range order (periodic or quasiperiodic) on lattice dynamics, we have carried out inelastic x-ray and neutron scattering experiments on single grain samples of the Zn-Mg-Sc icosahedral quasicrystal and of the Zn-Sc periodic cubic 1/1 approximant. Besides the overall similarities and the existence of a pseudo gap in the transverse dispersion relation, marked differences are observed, the pseudo gap being larger and better defined in the approximant than in the quasicrystal. This can be qualitatively explained using the concept of pseudo Brillouin zone in the quasicrystal. These results are compared to simulations on atomic models and using oscillating pair potentials which have been fitted against ab-initio data. The simulated response function reproduces both the dispersion relation but also the observed intensity distribution in the measured spectra. The partial vibrational density of states, projected on the cluster shells, is computed from this model.

Mots clés: Physical Sciences

Marek Mihalkovic, Sonia Francoual, Kaoru Shibata, Marc de Boissieu, a Q.R. Baron, et al.. Atomic dynamics of the i-ScZnMg and its 1/1 approximant phase: experiment and simulation. Philosophical Magazine, 2008, 88 (13-15), pp.2311-2318. ⟨10.1080/14786430802077909⟩. ⟨hal-00513888⟩