Compression-rate dependence of pressure-induced phase transitions in Bi

Abstract

It is qualitatively well known that kinetics related to nucleation and growth can shift apparent phase boundaries from their equilibrium value. In this work, we have measured this effect in Bi using time-resolved X-ray diffraction with unprecedented 0.25 ms time resolution, accurately determining phase transition pressures at compression rates spanning five orders of magnitude (10–2–103 GPa/s) using the dynamic diamond anvil cell. An over-pressurization of the Bi-III/Bi-V phase boundary is observed at fast compression rates for different sample types and stress states, and the largest over-pressurization that is observed is ΔP = 2.5 GPa. The work presented here paves the way for future studies of transition kinetics at previously inaccessible compression rates.

Dynamic compression of Ce and Pr with millisecond time-resolved X-ray diffraction

“…In contrast, the onset transition pressure of the Pr-III to Pr-IV VC transition increases as the compression rate increases , in agreement with results from the ramp compression study of Bastea and Reisman 35 . Similar behavior was observed in Bi, where the Bi-III to Bi-V transition is observed at higher pressures at faster compression rates 16 . This may be characteristic of structural transitions where atomic rearrangements occur.…”

“…Time-resolved synchrotron X-ray diffraction experiments were performed on dynamically-compressed Ce and Pr samples at the Extreme Conditions Beamline (ECB, P02.2) at PETRA III 44 using the LLNL dDAC design 14 . The experimental setup was described in greater detail by Husband et al 16 . Data were collected using a 25.6 keV (~ 0.4843 Å) incident X-ray beam focused to a ~ 8(h) × 3(v) μm 2 spot using compound refractive lenses.…”

“…This, in turn, could result in a shift of the phase transition pressure to higher or lower pressures, depending on the P–T slope of the phase boundary. However, the extremely high thermal conductivity of the diamond anvils (2000 W/mK at ambient pressure) means that samples that are in contact with the diamond cool on μs timescales 15 , and so the possibility of sample heating has typically been ignored in previous dDAC experiments 16 .…”

Femtosecond Diffraction and Dynamic High Pressure Science

“…It also raises the possibility that the phases seen under extreme P-T conditions in short-lived laser compression experiments are not necessarily the equilibrium phases existing under the same P-T conditions within planets: a fact that reinforces the weight of our view that a degree of circumspection is advised when attempting to directly relate dynamic experiments to static contexts. We are only starting to make progress in this area, where the results from static compression, dynamic DAC 150 , impactor, and laser compression experiments will be required in order to probe sample behaviour over strain rates spanning 9 orders of magnitude.…”

A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell

“…Although the next generation of photon-counting detectors promises about a tenfold increase in collection rate, this is still far from what is required to utilize the full dDAC capabilities. Synchrotron experiments are further limited by the available flux, where high-frame-rate data collection is limited to mid-or high-Z materials (Husband, O'Bannon et al, 2021 as low-Z materials require much longer exposure times [e.g. $ 100 ms for H 2 O (Me ´ndez et al, 2021) and $ 1 s for Li (Frost et al, 2019)].…”