The study of the dynamic properties of quasicrystals, especially vibrational excitations, is of considerable interest for understanding their unique atomic structure and the associated physical characteristics. Inelastic neutron scattering is a powerful tool for probing these excitations, providing information on phonon spectra and interatomic interactions.
This paper presents the results of studies of inelastic neutron scattering on an icosahedral AlFeCu quasicrystal. The experiments were carried out on a high-resolution neutron spectrometer. The data obtained allowed us to determine the phonon state density function in a wide energy range.
Analysis of experimental data revealed features in the phonon spectrum characteristic of a quasi-crystalline structure, in particular, the presence of a pseudo-gap near the Fermi energy. The influence of icosahedral symmetry on the dynamic properties of the quasicrystal under study is discussed. The results obtained are compared with theoretical calculations and data from other experimental methods.
For a more detailed study of the lattice dynamics, measurements were carried out at different temperatures. The temperature dependence of the phonon spectrum allowed us to estimate the anharmonic effects and the contribution of various vibrational modes to the heat capacity of the quasicrystal. It was found that with increasing temperature, the phonon peaks broaden and their position shifts, which indicates an increase in the role of anharmonic interactions.
Comparison of the obtained data with the results obtained for related crystalline alloys allowed us to identify specific features of the phonon spectrum caused by the quasi-crystalline structure. In particular, an increase in the density of states in the low-energy region is observed, which may be associated with the presence of localized vibrational modes arising due to the disorder of the atomic structure.
The conducted research allowed to obtain valuable information about the dynamic properties of the icosahedral quasicrystal AlFeCu. The obtained data can be used to develop more accurate theoretical models describing the structure and physical properties of quasicrystals.
In conclusion, it should be noted that further studies using higher-resolution inelastic neutron scattering methods and on other quasi-crystalline systems will undoubtedly contribute to understanding the complex dynamics of these unique materials.
Author: M. Quilichini, B. Hennion, G. Heger
Institute: Léon Brillouin Laboratory (CEA-CNRS), CEN-Saclay, 91191 Gif-sur-Yvette, France