Local structure of solid Rb at megabar pressures

摘要: We have investigated the local and electronic structure of solid rubidium by means x-ray absorption spectroscopy up to 101.0 GPa, thus doubling maximum experimental pressure. This study confirms predicted stability phase VI was completed combination two pivotal instrumental solutions. On one side, we made use nanocrystalline diamond anvils, which, contrary more commonly used single crystal do not generate sharp Bragg peaks (glitches) at specific energies that spoil weak fine oscillations in cross section. Second, exploited performance a state-of-the-art focussing device yielding beam spot size 5 × μm2, spatially stable over entire energy scan. An advanced data analysis protocol implemented extract pressure dependence structural parameters Rb from 51.2 GPa highest A continuous reduction nearest neighbour distances observed, reaching about 6% probed range. also discuss phenomenological model based on Einstein approximation describe behaviour mean-square relative displacement. Within this simplified scheme, estimate Gruneisen parameter for high be 1.3–1.5 interval.