A new spectroscopy method reveals accelerated relaxation dynamics in cerium-based compressed metallic glass

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Two-time correlation functions of ce-based MG measured by HP-XPCS at different pressures during compression. With each press, the width of the reddish diagonal outline is proportional to the relaxation time, which widens below 2.9 GPa and then narrows during further compression. Credit: Dr. Qiaoshi Zeng of HPSTAR

A major obstacle in our understanding of glass and glass phenomena is the elusive relationship between relaxation dynamics and glass structure. A team led by Dr. Qiaoshi Zeng of HPSTAR recently developed a novel in situ high-pressure wide-angle X-ray photon correlation spectroscopy method to enable dynamic studies of atomic-scale relaxation in metallic glass systems subjected to extreme pressures. The study is published in Proceedings of the National Academy of Sciences (PNAS).

Metallic glasses (MG), with many properties superior to both metals and conventional glasses, have been the focus of worldwide research. As thermodynamically metastable materials, like typical glasses, MGs spontaneously evolve into their most stable states all the time through various dynamic relaxation behaviors.

These relaxation behaviors have significant effects on the physical properties of MGs. However, until now, the ability of scientists to further their understanding of the relaxation dynamics of glass and in particular its relationship to atomic structures has been limited by the available techniques.

“Thanks to recent improvements in synchrotron X-ray photon correlation spectroscopy (XPCS), it is possible to measure the collective particle motions of glassy samples with a high resolution and a large coverage in the time scale, and thus, various processes otherwise inaccessible microscopic dynamics have been explored with glasses,” said Dr. Zeng.

“However, the change in atomic structures is subtle in previous measurements of the relaxation process, which still makes it difficult to probe the relationship between structure and relaxation behavior. To overcome this problem, we decided to employ high pressure because it can effectively alternate the structure of various materials, including MG.”

To this end, the team developed in situ high-pressure synchrotron wide-angle XPCS for probing a cerium-based MG material during compression. In situ high-pressure wide-angle XPCS revealed that collective atomic motion initially slows down, as generally expected with increasing density. It then, counterintuitively, accelerates with further compression, exhibiting an unusual dynamic crossover of nonmonotonic pressure-induced constant relaxation at ~3 GPa.

Furthermore, combining these results with in situ high-pressure synchrotron X-ray diffraction, the relaxation dynamics anomaly is closely related to dramatic changes in local atomic structures during compression, rather than monotonic scaling with sample density. or your overall stress level.

‘As the density increases, the atoms in the beaker generally become more difficult to move or spread out, slowing its relaxation dynamics. This is what we normally expect from hydrostatic compression,’ explained Dr. Zeng.

“So the non-monotonic relaxation behavior observed here in cerium-based MG under pressure is quite unusual, indicating that in addition to density, structural details could also play an important role in the relaxation dynamics of the glass,” explained the dr. Zeng.

These results demonstrate that there is a close relationship between the relaxation dynamics of glass and the atomic structures in MGs. The technique developed here by Dr. Qiaoshi Zeng’s group can also be extended to explore the relationship between relaxation dynamics and atomic structures in various glasses, especially those significantly tunable by compression, providing new opportunities for relaxation dynamics studies glass under extreme conditions.

More information:
Qiaoshi Zeng et al, Pressure-induced non-monotonic crossing of constant relaxation dynamics in a metallic glass, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.230228112

About the magazine:
Proceedings of the National Academy of Sciences

Provided by the Center for High Pressure Science & Technology Advanced Research

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