Author: Sota Takagi, Atsushi Kyono, Saki Mitani, Neo Sugano, Yuki Nakamoto, Naohisa Hirao

Institute: Department of Earth Evolutionary Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan

The X-ray diffraction study of the icosahedral AlCuFe quasicrystal at megabar pressures represents an important step in understanding the physical properties of quasicrystalline structures. Experiments conducted at different pressure levels investigated the relationship between the structural temperature and the symmetry of the crystal lattice. X-ray diffraction made it possible to accurately determine the lattice parameters and to identify patterns characteristic of the transition to a new phase.

We present the results of in-situ synchrotron X-ray diffraction study of icosahedral (i)-AlCuFe (QC) quasicrystal at high pressure up to 104 GPa and at room temperature using the diamond anvil cell method. During compression, no noticeable changes in the diffraction pattern are observed at all studied pressures. Five characteristic peaks of i-AlCuFe QC are preserved up to 104 GPa. The unit cell volume of i-AlCuFe QC consistently decreases up to 72 GPa. The experimental compression curve showed PV 0 = 2023(19)Å3, 0 = 131(7) GPa, K,’ = 4.0 (fixed). The obtained EoS parameters correspond to those recorded in previously conducted studies. A continuous change in volume is observed in the range from 72 to 75 GPa. These data indicate a phase transition from i-AlCuFe QC to an approximating crystal (AC) with a similar local arrangement of atoms. The study confirms that the i-AlCuFe QC structure remains stable at least up to 72 GPa, after which a transition to AC occurs with minor displacement of atoms.

The results obtained confirm the existence of stable quasi-crystalline states that retain their unique symmetry even under extreme conditions. Analysis of diffraction patterns showed changes in the arrangement of atoms, indicating the emergence of new interatomic interactions. These interactions can significantly affect the mechanical and thermal properties of materials.

The study of AlCuFe as a model of systems with a hierarchical structure is of great importance for the creation of new materials with specified properties. The results of the study open new horizons for further search and development of quasicrystals that can find application in various fields of science and technology.