DETERMINATION OF EQUATION OF STATE OF AMORPHOUS MATERIALS AT HIGH PRESSURE USING NANOSCALE TRANSMISSION X-RAY MICROSCOPY
Group IV elements, including carbon, silicon, and germanium, both alone and in combination, exhibit a variety of amorphous forms that show unique behavior upon compression. Compressing glassy carbon above 40 GPa, we observed a new carbon allotrope with a fully sp3-bonded amorphous structure and diamond-like strength. Amorphous SiO2 and GeO2 are classic network-forming glasses which display rich structural polymorphism at high pressure. We used TXM for accurate P-V determination of glassy carbon, SiO2 glass, and GeO2 glass in a cross diamond anvil cell. The results provide guidance for understanding the mechanisms of the structure and bonding changes in these amorphous materials at high pressure.