An Analytic X-Ray Absorption Near-Edge Spectroscopy Model for Compressed Fe₂O₃

Understanding various electronic and magnetic changes at high pressures in Fe₂O₃ is not only an important solid-state physics question, but is crucial in describing Earth’s lower mantle. An x-ray absorption platform is being developed at the Laboratory for Laser Energetics to understand the electronic and crystal structure of compressed materials by simultaneously measuring x-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption fine structure. Fe₂O₃ was quasi-ramp compressed up to 700 GPa and the pressure was determined using a velocity interferometry system for any reflector (VISAR) on the OMEGA-60 laser. An analytic method to extract the electronic occupation and temperature of the compressed sample from the XANES edge is being developed and compared to electronic structure calculations from ab initio molecular-dynamics simulations based on density function theory.