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Résumé |
Recent advances in instrumentation and data-analysis allowed us to perform x-ray absorption (XAS) studies of liquids, undercooled liquids and glasses under high-temperature and high-pressure conditions [1, 2]. XAS is used as a probe for the local structure, X-ray diffraction (XRD) for measuring long-range ordering, checking the sample status and determining relevant environmental parameters (pressure), while single-energy X-ray absorption temperature or pressure scans are used to detect and study phase transitions. Reliable reconstruction of the structure of disordered systems by combining XAS and XRD can be now obtained using Reverse Monte Carlo (RMC) simulations implemented into modern XAS data-analysis algorithms (RMC-GnXAS)[1]. The experimental set-up used for combined XAS and X-ray diffraction synchrotron radiation experiments will be briefly presented as well as advances in XAS data-analysis allowing detailed structural insight about pair and higher-order distributions. In the seminar I will try to show the potential of the techniques in measuring and understanding disordered matter under extreme conditions, illustrating new results on liquid Sn under pressure [2] as compared to liquid Cu [1].
[1] A. Di Cicco et al, Phys. Rev. Lett. 91, 135505 (2003).
[2] A. Di Cicco et al, Appl. Phys. Lett. 89, 221912 (2006).
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