MR11A-02
High-energy X-ray diffraction of melts and amorphous solids at extreme conditions

Monday, 14 December 2015: 08:12
301 (Moscone South)
Clemens Prescher1, Tony Yu1, Yanbin Wang2, Peter J Eng3, Lawrie B Skinner4, Joanne Stubbs3 and Vitali Prakapenka2, (1)University of Chicago, Center for Advanced Radiation Sources, Chicago, IL, United States, (2)University of Chicago, Chicago, IL, United States, (3)The University of Chicago, Argonne, IL, United States, (4)Stony Brook University, Mineral Physics Institute, Stony Brook, NY, United States
Abstract:
The structural analysis of amorphous materials, glasses and liquids at extreme conditions using X-ray diffraction is a very challenging endeavor. The samples are typically very small and surrounded by pressure vessels, which result in a huge background signal which may be orders of magnitude stronger than the actual sample signal. Furthermore, the background signal changes during compression in diamond anvil cells (DAC), making analysis of the diffraction data impossible at large pressures (>60 GPa). A key factor for obtaining high quality structural data is the maximum obtainable Q of the data collection. While at ambient conditions a maximum Q of more than 20 Å-1 has become standard, at high pressures data have been reported and analyzed with a maximum Q as low as 7 Å-1, which significantly reduces the resolution of the obtained real space data for multicomponent systems.

In order to overcome those challenges, we have successfully installed a multichannel collimator (MCC) for the DAC setup at APS/GSECARS 13-IDD and for the Paris Edinburgh Press (PEP) at 13-IDC. The MCC leads to a significant increase in signal to background ratio and the background remains almost constant during compression in a DAC and removes the additional diffraction signal from the pressure media in the PEP.

The combination of MCC and the high-energy X-ray optics of the 13ID beamline enables data collection of melts, glasses and amorphous materials up to 10 GPa in the PEP with a maximum Q of about 16 Å-1 and the collection of amorphous materials and glasses up to pressures above 150 GPa with a maximum Q of about 13 Å-1, thus, enabling the structural investigation of amorphous materials at much larger pressures than previously achievable.

Further, we have developed several new user-friendly software packages for the analysis of X-ray diffraction data with specific data reduction and optimization algorithms for the analysis of amorphous materials at high-pressure.

In order to show the capabilities of the new setups we will present results on the structure of selected melts up to 6 GPa measured in the PEP and on the structure of SiO2 glass up to 180 GPa.

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