Controlled High Pressure High Temperature Phase Diagram Scanning with Self-Heating Diamonds*

Further advances have been made in the control systems for self-heating diamond anvils, which incorporate laser-etched heating circuits on a pair of metal-sputtered diamond anvils to create a doublesided heating setup. This allows for rapid (100 K/s) heating and cooling rates, with precision limited by measurement rate. Thermally insulating alumina seats and water cooling prevent thermal expansion in the cell body and allow for continuous measurement without realignment of the sample. This system is also portable, allowing it to be incorporated in diffraction measurements at synchrotron.

The Raman microscopy setup at LLNL incorporates a dedicated detector system to measure pressure and drive an automated gas membrane controller. Combined with the temperature control, this allows for Raman measurements to be taken along any arbitrary pre-selected path in P-T space.

Here we present Raman measurements across the phase diagrams of nitrogen and several ammonia compounds. We also present x-ray diffraction scans of various metals taken at synchrotron. The methods and software used to analyze both types of data sets are presented.