High-pressure X-ray absorption fine structure in the diamond anvil cell and its applications in geological materials

Abstract

Although coupling the X-ray absorption fine structure (XAFS) technique to the diamond anvil cell (DAC) has long been recognized as potentially important for understanding the behavior and evolution of the local and electronic structure of matter under extreme conditions, the DAC has been regarded as poorly suited for XAFS due to the DAC imposed glitches. Recently, an iterative method was proposed to distinguish and eliminate the serious interference of the diamond Bragg peaks, and succeeded in acquiring high quality ‘reflection-free’ XAFS spectra at high pressure under the DAC environment. In this paper, we use this method and present demonstration XAFS spectra for GeO2 glass, which is the archetype of network forming glasses with important geophysical implications, at pressures to 64 GPa. This is far above the change in coordination from tetrahedra to octahedra occurring at 6-13 GPa. The results provide important insight into the structural polymorphism of GeO2 glass at high pressure.