Pressure-induced transformations in Ce-Al metallic glasses: The role of stiffness of interatomic pairs

When high pressure is applied to Ce-Al metallic glasses, their disordered atomic structure exhibits some unusual properties like polyamorphism or transformation into a crystalline phase. In this work, we probe the atomic arrangement of Ce₅₅Al₄₅ and Ce₇₅Al₂₅ glasses by X-ray absorption spectroscopy and X-ray diffraction in the pressure range of 0–30 GPa. The pressure-dependent parameters of local environment of cerium atoms are evaluated by extended X-ray absorption fine structure (EXAFS) fitting. We demonstrate that due to compositional dependence of stiffness of Ce-Al pairs, densification of Ce55Al45 is accompanied by an increase of atomic size mismatch between Ce and Al stabilizing the amorphous phase, while a decrease of the mismatch is observed in Ce₇₅Al₂₅ alloy which eventually leads to its devitrification at 25 GPa.