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Structure and dynamics of glasses: using novel X-ray tools to push the boundaries of how we understand them

Periodic Reporting for period 1 - GlassX (Structure and dynamics of glasses: using novel X-ray tools to push the boundaries of how we understand them)

Période du rapport: 2021-08-23 au 2023-08-22

The goal of the GlassX action is to study the structural and dynamical properties of disordered systems (glasses and liquids), using a combination of X-rays and other measurements techniques.

Glasses are ubiquitous in our daily lives, yet the current understanding of them is very limited. Despite decades of research, the structure and dynamics of glasses and the nature of the glass transition remain open problems in physics. With the advent of a new generation of X-ray sources and the development of novel X-ray technologies, these challenges can now be addressed. The GlassX action thus aims at exploiting these new opportunities to significantly better our understanding of glasses. This is important both from a fundamental science point of view, since a comprehensive description of glasses has long been sought after by physicists, and from a practical point of view, since metallic glasses have important industrial applications as well.

The action is divided into four parts, each addressing an important open question in glass physics. Parts 1 and 2 focus on structural properties of vapor-deposited metallic glasses, including the degree of local anisotropy and the relation between their structure and stability. Parts 3 and 4 concentrate on the dynamics of glasses, including the wave-vector dependence and the existence of dynamic heterogeneities. These projects will make use of X-ray nano-diffraction and X-ray photon correlation spectroscopy techniques, both of which will see significant improvements with the newly available fourth-generation X-ray sources, making it possible to reach previously unexplored length and time scales.
Since the beginning of the project, I have led many experiments both at the host institution and at synchrotron X-ray sources to study the properties of glasses and liquids. In particular, I have been the Proposer / Principal Investigator of the following experiments at major X-ray facilities:
• European XFEL (Germany), proposal 3346, “Radiation effects in phase change materials”, 28/03/2023 – 01/04/2023.
• ESRF (France), proposal HC-5097, “Studying the laser amorphization of tellurium”, 24/01/2023 – 30/01/2023.
• ESRF (France), proposal HC-4904, “Studying the long-wavelength dynamics in glass-forming liquids”, 12/04/2022 – 16/04/2022.
• ESRF (France), proposal HC-4889, “Probing nano-scale heterogeneities in metallic glasses”, 07/04/2022 – 11/04/2022.
• ESRF (France), proposal HC-4683, “Studying anisotropies in vapor-deposited metallic glasses”, 26/01/2022 – 29/01/2022.
In addition, I have participated in many other experiments together with members of my current research group to study the thermodynamics and dynamics of glasses.

Given the relatively long turnaround time of projects involving synchrotron X-ray sources (usually one to a few years), there is ongoing work to analyze data and write up the manuscript(s). One project, corresponding to Part 1 of the action, has resulted in a recent publication:
[P. Sun et al., "Observation of long-range anisotropy in a vapor-deposited metallic glass," Materialia, Vol. 30, 101847 (2023).]
This work is presented as a poster for the 9IDMRCS conference (August 2023, Japan). More dissemination activities are planned for the future.

In addition, I have submitted experimental reports which summarize the preliminary results.

In the following year(s), I will continue working on these projects and disseminate the results in the form of scientific publications and conference presentations.
Overall, the GlassX action aims to go beyond the state of in the study of disordered systems (glasses and liquids).

While work is ongoing and will continue after the end fo the project, Part 1 of the action has been completed and we have demonstrated, for the first time to our knowledge, direct observation of long-range structural anisotropy in a metallic glass sample. In other words, the average structure of this sample is different in different directions, even though it appears completely amorphous. This implies that, even though glasses do not have any periodic structure as in crystals, they must still have locally ordered structures on the nanometer scale. Furthermore, these local structure can find a way to align with each other with long-range correlations, a behavior that is unexpected for glasses and almost never considered in the models. Therefore, our results call for further studies to renew the structural description of amorphous materials.

More detailed information can be found in the publication [P. Sun et al., "Observation of long-range anisotropy in a vapor-deposited metallic glass," Materialia, Vol. 30, 101847 (2023)]
Publication [Sun et al., Materialia (2023)]
Graphical abstract for the publication [Sun et al., Materialia (2023)]