Uncovering the bridging role of slow atoms in unusual caged dynamics and β-relaxation of binary metallic glasses

YX Chen and SD Feng and XQ Lu and SP Pan and CQ Xia and LM Wang, JOURNAL OF CHEMICAL PHYSICS, 158, 134511 (2023).

DOI: 10.1063/5.0146108

The origin of beta-relaxation in metallic glasses is still not fully understood, and the guidance of slow atoms for caged dynamics and beta- relaxation is rarely mentioned. Using molecular dynamics simulations, we reveal the bridging role of slow atoms on unusual caged dynamics and beta-relaxation. In the stage of unusual caged dynamics, slow atoms are bounded by neighboring atoms. It is difficult for the slow atoms to break the cage, producing more high-frequency vibration, which causes more atoms to jump out of the cage randomly in the next stage. Precisely, the movement of the slow atoms changes from individual atoms vibrating inside the cage and gradually breaking out of the cage into a string-like pattern. The string-like collective atomic jumps cause decay of the cages, inducing beta-relaxation. This situation generally exists in binary systems with the large atomic mass difference. This work offers valuable insights for understanding the role of slow atoms in unusual caged dynamics and beta-relaxation, complementing studies on the origin of beta-relaxation in metallic glasses and their glass-forming liquids.

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