Mircobeam X-ray total scattering experiments at the high-pressure beamline X17B3 at the National Synchrotron Light Source

Structure of minerals under extreme conditions of high pressure and temperature is very important in Geosciences. The total scattering pair distribution function (PDF) technique using high energy X-ray microbeam to access a large range of scattering vector, e.g. 20Å-1-40Å-1, is an emerging structural analysis method in high pressure research, which allows simultaneous probing of local, intermediate and long-range structure in crystalline, amorphous or complex materials[1-3]. Using high-energy X-rays of 80 keV at X17B3 beamline, National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, PDF measurements has been carried out by users from multiple disciplines [4]. At this AGU meeting, we will present the current status of high-pressure total scattering pair distribution function (PDF) measurements and recent achievements on the availability of high energy X-ray microbeam at X17B3 beamline, NSLS. Accurate X-ray energy calibration is indispensable for X-ray energy-sensitive scattering and diffraction experiments, but there is still a lack of effective methods to precisely calibrate the high energy X-ray beam, because precise energy calibration XAS is problematic due to the lack of suitable X-ray absorption edges at the desired high energy. We have recently proposed an iterative method [5] for a precise and fast X-ray energy calibration over a wide range, including high energy X-ray beam for PDF measurements. Some PDF measurements on the geophysical important materials, such as GeO2 and SiO2 materials, under ambient and high-pressure using diamond anvil cell will be presented. References: 1. Billinge, S.J.L., The atomic pair distribution function: past and present. Zeitschrift für Kristallographie, 2004. 219(3-2004): p. 117-121. 2. Billinge, S.J. and I. Levin, The problem with determining atomic structure at the nanoscale. Science, 2007. 316(5824): p. 561-5. 3. Billinge, S.J.L., et al., Characterisation of amorphous and nanocrystalline molecular materials by total scattering. CrystEngComm, 2010. 12(5): p. 1366-1368. 4. Ehm, L., et al., Evidence of tetragonal nanodomains in the high-pressure polymorph of BaTiO3. Applied Physics Letters, 2011. 98(2): p. 021901-3. 5. Hong, X., Z. Chen, and T.S. Duffy, Absolute x-ray energy calibration over a wide energy range using a diffraction-based iterative method. Review of Scientific Instruments, 2012. 83(6): p. 063901-10.