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

• Published in: Philosophical magazine (2003. Print) Vol. 88; no. 13-15; pp. 2311 - 2318
• Main Authors: Mihalkovič, M., Francoual, S., Shibata, K., Boissieu, M. De, Baron, A.Q.R., Sidis, Y., Ishimasa, T., Wu, D., Lograsso, T., Regnault, L. -Pierre, Gähler, F., Tsutsui, S., Hennion, B., Bastie, P., Sato, T.J., Takakura, H., Currat, R., Tsai, A.-P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Abingdon Taylor & Francis Group 01-05-2008; Taylor & Francis
• Subjects: Chemical and Process Engineering; Chemical Sciences; Condensed matter: structure, mechanical and thermal properties; Engineering Sciences; Exact sciences and technology; Lattice dynamics; Material chemistry; phonons; Physics; Quasicrystals; Semi-periodic solids; Structure of solids and liquids; crystallography; Vibrational states in disordered systems; Cubic lattices; Pair potentials; Brillouin zones; Magnesium alloys; Ternary alloys; Response functions; Quasicrystals; Quasi periodic structure; Zinc alloys; Shell models; Local structure; Energy gap; X-ray scattering; Ab initio calculations; Model potential; Scandium alloys; Dispersion relations; Digital simulation; Long-range order; Theoretical study; Phonon density of states; Physical properties; Icosahedral phase; Approximant; Lattice dynamics; Atomic models
• ISSN: 1478-6435; 1478-6443; 1478-6433
• DOI: 10.1080/14786430802077909

Quasicrystals are long-range ordered materials that 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.