Materials properties of defect-stabilized off-stoichiometric τ-phase Al2Ge2Mg

0585613 - ÚFM 2025 RIV GB eng J - Journal Article
Friák, Martin - Zobač, Ondřej - Chlup, Zdeněk - Fikar, O. - Papež, Pavel - Zelený, M. - Kroupa, Aleš
Materials properties of defect-stabilized off-stoichiometric τ-phase Al2Ge2Mg.
Intermetallics. Roč. 169, Jun (2024), č. článku 108294. ISSN 0966-9795. E-ISSN 1879-0216
R&D Projects: GA ČR(CZ) GA22-22187S
Institutional support: RVO:68081723
Keywords : Al-Ge-Mg * Defects * Stability
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 4.4, year: 2022
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S0966979524001134?via%3Dihub

We have performed a quantum-mechanical study of off-stoichiometric Al2Ge2Mg τ-phase intermetallic com pounds. Our calculations focused on evaluating the formation energy of static lattices, their elastic properties as
well as free energy of formation including phonon contributions. While the stoichiometric Al2Ge2Mg τ phase was
found thermodynamically, mechanically and dynamically stable, we have identified an off-stoichiometric
composition Al7Ge8Mg5 which exhibits the free energy of formation lower than the stoichiometric compound.
The Al7Ge8Mg5 was found both mechanically and dynamically stable as well. This off-stoichiometric compound
has Mg atoms located also at the Al sublattice, i.e. these defects exhibit a stabilizing effect. Phonon contributions
into the free energy of formation have turned out to be crucial for a proper description of the thermodynamic
stability. In contrast, several other off-stoichiometric states are significantly thermodynamically destabilized by
anti-site atoms at the Ge sublattice. The formation energy and the homogenized polycrystal Young’s modulus are
found anti-correlated indicating a connection between the thermodynamic and mechanical stability. Regarding
the theoretical values of homogenized polycrystal Young’s moduli, our measurements resulted in values quite
close to the predicted ones.
Permanent Link: https://hdl.handle.net/11104/0353300