Icosahedral quasicrystals, with their unique aperiodic structure, represent an intermediate state between periodic crystals and amorphous glasses. Studying the dynamic properties of these materials is critical to understanding their fundamental characteristics and potential applications. This paper is devoted to a comparative study of the lattice dynamics of an icosahedral quasicrystal and Al77Cu13V10 glass using inelastic neutron scattering (INS).
The INS method, being a powerful tool for studying collective excitations in condensed media, allows obtaining information on phonon spectra and density of vibrational states. Comparative analysis of INS data obtained for the Al77Cu13V10 quasicrystal and glass allows revealing differences in their dynamic properties caused by differences in structure.
Analysis of the structure of the icosahedral quasicrystal and amorphous Al77Cu13V10 revealed the presence of a common nanoscale structural component – an icosahedral atomic cluster. In the amorphous material, a dense, chaotic packing of these clusters is observed, devoid of long-range orientational order. Therefore, the icosahedral quasicrystal and amorphous Al77Cu13V10 are valuable objects for studying the dynamics of disordered substances.
We have investigated the dynamic structure factors S(Q,ω) of icosahedral and amorphous Al77Cu13V10, as well as a crystallized analogue, at room temperature using the inelastic neutron scattering method. The experiments were carried out on time-of-flight spectrometers with LAM-40 crystal analyzers located in KENS. A generalized function of the vibrational density of states G(ω) was obtained. Low-energy excitations in the energy range up to 8 meV were detected in icosahedral and amorphous Al77Cu13V10.
Despite significant differences in the static structural factors S(Q) of icosahedral and amorphous Al77Cu13V10, their dynamic characteristics are almost identical and differ significantly from the dynamics of the crystallized sample.
In particular, for a quasicrystal, a broadening of phonon lines and the presence of characteristic features in the density of vibrational states associated with the presence of localized modes and a fractal structure are observed. At the same time, for glass, a more diffuse picture is observed, characteristic of amorphous systems with a wide distribution of interatomic distances.
The obtained results allow us to better understand the influence of the aperiodic structure on the dynamic properties of quasicrystals and can be used to develop new materials with specified characteristics. Further research is aimed at studying the influence of temperature and pressure on the lattice dynamics of quasicrystals and glasses.
Author: Kaoru Shibata, Hiroshi Mizuseki, An Pang Tsai, Kenji Susuki
Institute: Institute of Materials Science, Tohoku University, Katahira 2-1-1, Aobaku, Sendai 980-77, Japan