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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
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Universal amorphous-amorphous transition in GexSe100-x glasses under pressure.
Can Yildirim1,2, Matthieu Micoulaut2, Punit Boolchand3
1SPIN-Université de Liège, Institut de Physique B5, 4000 Sart-Tilman, Belgium.
Scientific Reports
|June 9, 2016
Summary
Pressure alters the structure of vitreous GeSe alloys, causing unique changes in atomic distances and angles. These amorphous materials exhibit a two-step structural response to pressure, indicating a metallization event around 15-20 GPa.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Solid State Chemistry
Background:
- Vitreous chalcogenides like Ge-Se alloys are technologically important materials.
- Understanding their response to external stimuli, such as pressure, is crucial for material design.
- Previous studies have explored structural properties, but pressure-induced metallization requires further investigation.
Purpose of the Study:
- To investigate pressure-induced structural modifications in vitreous GexSe100-x alloys.
- To determine the behavior of interatomic distances, angle distributions, and coordination numbers under high pressure.
- To elucidate the mechanism of densification and potential metallization in these amorphous materials.
Main Methods:
- X-ray absorption spectroscopy (XAS) for probing local atomic environments.
- X-ray diffraction (XRD) for structural analysis.
- Ab initio molecular dynamics (AIMD) simulations for detailed densification mechanisms and comparison with experimental data.
Main Results:
- All compositions remained amorphous up to 42 GPa.
- A two-step response in Ge-Se interatomic distances was observed, with an increase around 15-20 GPa.
- Evidence of metallization was detected via Ge K-edge energy shifts and structure factor analysis.
- AIMD simulations confirmed experimental findings on densification and structural evolution.
Conclusions:
- Vitreous GeSe alloys exhibit universal structural changes under pressure, independent of composition.
- The observed increase in interatomic distance is linked to a pressure-induced metallization event.
- Combined experimental and computational methods provide a comprehensive understanding of structural modifications in these materials.
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