A scanning angle energy-dispersive X-ray diffraction technique for high-pressure structure studies in diamond anvil cells

Abstract

A scanning angle diffraction technique with an energy-dispersive solid-state detector (SSD) and white synchrotron radiation has been developed for high-pressure structure studies in diamond anvil cells (DACs). This technique is similar to the CAESAR technique [Y. Wang, T. Uchida, R. Von Dreele, M.L. Rivers, N. Nishiyama, K. Funakoshi, A. Nozawa, and H. Kaneko, A new technique for angle-dispersive powder diffraction using an energy-dispersive setup and synchrotron radiation, J. Appl. Cryst. 37 (2004), p. 947] developed for large-volume presses, but extended to DAC applications with high spatial resolution. The main feature of the technique is the well-defined collimation in the beam path to the detector, which improves the signal-to-noise ratio significantly, compared to routine monochromatic angle-dispersive powder diffraction with area detectors. This is particularly useful and essential for low-scattering materials and for amorphous and liquid diffraction/scattering studies using DACs. Data collected from crystalline and amorphous samples in DACs show that a coarse 2θ scan (0.1–0.2° for crystals and 0.5° for amorphous structure) is sufficient to obtain reasonable diffraction resolution. The scanning angle energy-dispersive X-ray diffraction technique provides angle-dispersive X-ray diffraction (ADXD) data in multiple energies. Such multi-energy ADXD data carry much more information than regular single-energy ADXD, which could provide site-specific atomic structure information for full structure refinement.

Keywords:

• diamond anvil cell
• energy-dispersive
• structure refinement
• amorphous
• anomalous X-ray scattering

Acknowledgements

We would like to thank M. Guthrie for helpful comments. This work was performed at HPCAT (Sector 16), Advanced Photon Source, Argonne National Laboratory. Part of the work was supported by an NSF grant (EAR-0738852). HPCAT was supported by DOE-BES, DOE-NNSA, NSF and W.M. Keck Foundation. APS was supported by DOE-BES, under Contract No. DE-AC02-06CH11357.