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Journal of synchrotron radiation 30(4), 671 - 685 (2023). doi:10.1107/S1600577523003910, An experimental platform for dynamic diamond anvil cell (dDAC) research hasbeen developed at the High Energy Density (HED) Instrument at the EuropeanX-ray Free Electron Laser (European XFEL). Advantage was taken of the highrepetition rate of the European XFEL (up to 4.5 MHz) to collect pulse-resolvedMHz X-ray diffraction data from samples as they are dynamically compressed atintermediate strain rates ( 10 3 s1), where up to 352 diffraction images can becollected from a single pulse train. The set-up employs piezo-driven dDACscapable of compressing samples in 340 ms, compatible with the maximumlength of the pulse train (550 ms). Results from rapid compression experimentson a wide range of sample systems with different X-ray scattering powers arepresented. A maximum compression rate of 87 TPa s1 was observed duringthe fast compression of Au, while a strain rate of 1100 s1 was achievedduring the rapid compression of N2 at 23 TPa s1., Published by Wiley-Blackwell, [Erscheinungsort nicht ermittelbar]

Physical review / B 107(22), 224108 (2023). doi:10.1103/PhysRevB.107.224108, Understanding the high-pressure behavior of ammonia hydrates is relevant for modeling the interior of solarand extrasolar icy bodies. We present here the results of high-pressure x-ray diffraction studies on ammonia-dihydrate (ADH) at room temperature (298 K) up to 112 GPa, employing both static and dynamic compressionexperiments performed in diamond anvil cells. The derived pressure-volume (P-V) compression curves arein excellent agreement regardless of the compression technique. In contrast to early theoretical predictions,our results indicate the stability of the disordered molecular alloy (DMA) phase, a body centered cubic (bcc)structure, and the absence of self-ionization in the investigated pressure range. By combining the P-V data fromseven different compression runs, we derive the first equation of state for ADH-DMA based on the third-orderBirch-Murnaghan formalism with best-fit parameters: V$_0$ = 23.96 ± 0.03 (Å$^3$ /molecule), B$_0$ = 9.95 ± 0.14 GPa,and B′$_0$ = 6.59 ± 0.03. The instantaneous bulk modulus directly derived from the quasicontinuous compressioncurves displays a smooth increase upon compression that further supports the absence of structural transitions., Published by Inst., Woodbury, NY

In this study, we investigated the phase stability of Al‐free and Al‐bearing superhydrous phase B (shy‐B) up to 55 GPa and 2500 K. In comparison with Al‐free shy‐B, the incorporation of 11.7 wt.% Al2O3 in shy‐B expands the stability by ∼400–800 K at 20–30 GPa. The determined dehydration boundary for Al‐bearing phase D indicates that it could be present even at normal mantle geotherm conditions at 30–40 GPa. Up to 23.8 mol.% Al2O3 can be dissolved into the structures of akimotoite and bridgmanite as a result of the decomposition reactions of Al‐bearing shy‐B and phase D between 20 and 40 GPa. Results of further experiments indicate that δ‐AlOOH is the stable hydrous phase coexisting with Al‐depleted bridgmanite at pressures above 52 GPa. This study shows that the incorporation of Al in dense hydrous magnesium silicates can have a profound impact on our picture of the water cycle in the deep Earth., Plain Language Summary: Constraining the deep cycle of water has a tremendous impact on our picture of the current state of the Earth and the evolution of the Earth's interior. Dense hydrous magnesium silicates (DHMSs) are considered potential H2O carriers in the Earth's mantle. However, the DHMSs can only be present at the relatively cold conditions of subduction slabs due their limited thermal stability. We determined the phase stability of Al‐bearing DHMSs at high pressure and temperature (P‐T) conditions. Our results show that the thermal stability of Al‐bearing shy‐B extends by 400–800 K with respect to its Al‐free counterpart at 600–800 km depth. The incorporation of Al also expands the phase stability of phase D and enhances the likelihood of its occurrence at normal mantle conditions at 800–1100 km. In addition, we observe that 23.8 mol.% Al2O3 can be dissolved into the structures of akimotoite and bridgmanite as a result of the decomposition reactions of Al‐bearing shy‐B and phase D between 600 and 100 km depth. Furthermore, δ‐AlOOH is the stable hydrous phase coexisting with Al‐depleted bridgmanite in the MgO‐SiO2‐Al2O3‐H2O system at pressures above 52 GPa and 1500 K., Key Points: In comparison with Al‐free shy‐B, the incorporation of 11.7 wt.% Al2O3 in superhydrous phase B (shy‐B) expands the stability by ∼400–800 K at 20–30 GPa. Al‐bearing phase D could be present even at normal mantle geotherm conditions at 30–40 GPa. δ‐AlOOH is the stable hydrous phase coexisting with Al‐depleted bridgmanite at pressures above 52 GPa., Center for Molecular Water Science, CMWS, https://doi.org/10.5281/zenodo.6320835

Journal of synchrotron radiation 28(6), 1747 - 1757 (2021). doi:10.1107/S1600577521009231, A laser heating system for samples confined in diamond anvil cells paired within situ X-ray diffraction measurements at the Extreme Conditions Beamlineof PETRA III is presented. The system features two independent laserconfigurations (on-axis and off-axis of the X-ray path) allowing for a broadrange of experiments using different designs of diamond anvil cells. The powerof the continuous laser source can be modulated for use in various pulsed laserheating or flash heating applications. An example of such an application isillustrated here on the melting curve of iron at megabar pressures. The opticalpath of the spectroradiometry measurements is simulated with ray-tracingmethods in order to assess the level of present aberrations in the system and theresults are compared with other systems, that are using simpler lens optics.Based on the ray-tracing the choice of the first achromatic lens and other aspectsfor accurate temperature measurements are evaluated., Published by Wiley-Blackwell, [S.l.]

Scientific reports 11(1), 14859 (1-9) (2021). doi:10.1038/s41598-021-94260-y, 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$^{–2}$–10$^3$ 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., Published by Macmillan Publishers Limited, part of Springer Nature, [London]