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

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.