Pressure-induced nonmonotonic cross-over of steady relaxation dynamics in a metallic glass

Abstract

Relaxation dynamics, as a key to understand glass formation and glassy properties, remains an elusive and challenging issue in condensed matter physics. In this work, in situ high-pressure synchrotron high-energy X-ray photon correlation spectroscopy has been developed to probe the atomic-scale relaxation dynamics of a cerium-based metallic glass during compression. Although the sample density continuously increases, the collective atomic motion initially slows down as generally expected and then counterintuitively accelerates with further compression (density increase), showing an unusual nonmonotonic pressure-induced steady relaxation dynamics cross-over at ~3 GPa. Furthermore, by combining in situ high-pressure synchrotron X-ray diffraction, the relaxation dynamics anomaly is evidenced to closely correlate with the dramatic changes in local atomic structures during compression, rather than monotonically scaling with either sample density or overall stress level. These findings could provide insight into relaxation dynamics and their relationship with local atomic structures of glasses.

Improvement of ultra-small-angle XPCS with the Extremely Brilliant Source

“…The data obtained are in good agreement with the theoretical estimates for ' 0.12. This demonstrates the feasibility of such measurements, which were challenging to perform earlier because of the lack of flux and small speckle contrast at this higher energy (Moron et al, 2022;Zhang et al, 2023). This opens new opportunities for the XPCS technique with this kind of sample environments and samples which require use of higher photon energies.…”

“…If needed, XPCS measurements can be performed even at higher energies, $ 20 keV, with a speckle contrast of 20%. This opens new perspectives for XPCS studies of highly absorbing samples and sample environments, such as a high-pressure cell that has thick diamond windows (Moron et al, 2022;Zhang et al, 2023).…”

“…In this region, the background scattering and sample scattering become closer, as shown by the SAXS profile in Fig.3of SI. This reduces by a factor of (1 + X) 2 , where X is the ratio of background to sample scattering intensity(Lhermitte et al, 2017;Chushkin, 2023). This factor can be obtained directly by considering a constant background intensity (I B ) and computing the correlation function on I Ã ðt; pÞ = I(t, p) + I B (p) instead of I(t, p).…”