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.
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