Pressure weakening unusual-caged dynamics of La80Al20 metallic glassforming liquid

YX Chen and S Feng and X Lu and H Kang and KL Ngai and L Wang, JOURNAL OF MOLECULAR LIQUIDS, 368, 120706 (2022).

DOI: 10.1016/j.molliq.2022.120706

Caged dynamics is the precursor of b-relaxation and is part of the complex relaxation dynamics of metallic glasses. However, limited by the lack of suitable experimental techniques, the pressure dependence of the caged dynamics of glass-forming metallic liquids and its underlying mechanism are still an open question to date. An unusual caged dynamics manifests a sudden drop near 0.1 ps in the partial nonGaussian parameter of Al atoms in metallic alloy La80Al20 liquid was recently found by molecular dynamics simulations. The present work investigates the caged dynamics of the La80Al20 liquid with strong atomic interactions under different pressures again by molecular dynamics simulations. It is found that the dominant polyhedra are transformed from the stable icosahedral- like polyhedra to the unstable ones that are compatible with crystal symmetry, resulting in the promotion of the rearrangement of atoms. These changes in turn cause the central Al atoms to be less hindered by the surrounding atoms, enhancing the cage-breaking motion and weakening the unusual caged dynamics. In addition, the applied pressure not only increases the diversity of vibrational frequencies but also weakens the difference in atomic vibrational amplitudes, leading to the weakening of the unusual caged dynamics. These findings provide new insights into the caged dynamics under pressure from the perspective of microstructure and vibrational properties. (c) 2022 Elsevier B.V. All rights reserved.

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