Parallel background subtraction in diamond anvil cells for high pressure X-ray data analysis

ABSTRACT

We present a simple and effective approach to improve X-ray data collected under extreme conditions of pressure and temperature. The X-ray data of the sample and the amorphous, liquid, or crystalline pressure transmitting media (PTM) which surround the sample are collected separately at each pressure and temperature, allowing a satisfactory background subtraction. Using this method, we are able to identify weak diffraction peaks of the low-Z elements Li and Na and amorphous silica under pressure and at cryogenic temperatures. In addition to exploration of phase diagrams of low-Z materials, this method can also be applied to recognize new phases of other unknown materials such as binary hydrides in the high pressure and high-temperature synthesis, and to allow deterministic identification of the onset pressure of structural phase transitions and the presence of mixed phases.

KEYWORDS:

• Diamond anvil cell
• high pressure
• low temperature
• X-ray diffraction
• low Z elements

Acknowledgements

We would like to acknowledge T. Bhowmick for the help of X-ray diffraction data collection on the amorphous silica and S. Tkachev in GSECARS for providing the helium gas loading and J. Smith, C. Kenney-Benson and R. Ferry in 16-ID-B for tremendous experimental support. The experimental work was performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Weizhao Cai http://orcid.org/0000-0001-7805-2108

Shanti Deemyad http://orcid.org/0000-0001-5661-8801

Additional information

Funding

This work was supported by Division of Materials Research [grant number 1351986]; National Nuclear Security Administration [grant number DE-NA-0002006,DE-NA0001974]. HPCAT operations are supported by DOE-NNSA under Award No. DE-NA0001974 with partial instrumentation funding by NSF. HPCAT beam time for these experiments was provided by the Carnegie-DOE Alliance Center, which is supported by DOE-NNSA under grant number DE-NA-0002006. Use of the COMPRES-GSECARS gas loading system was supported by COMPRES under NSF Cooperative Agreement EAR -1606856 and by GSECARS through NSF grant EAR-1634415 and DOE grant DE-FG02-94ER14466. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The research at University of Utah was supported by National Science Foundation-Division of Materials Research Award No. 1351986.