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Frontiers in Chemistry 11, 1166475 (2023). doi:10.3389/fchem.2023.1166475 special issue: "Celebrating the work of Prof. C. N. R. Rao: From Solid State to Materials Chemistry", We report the experimental discovery of a new structural phase of well-known orthorhombic R$_2$BaCuO$_5$ (R = Sm and Eu), exhibiting a tetragonal crystal structure with space group $P4∕mbm$. The high-pressure tetragonal phase is isostructural with the brown phase R$_2$BaCuO$_5$ (R = La, Pr, and Nd). In this structure, the Cu ions form an isolated square planar environment, contrary to the orthorhombic phase, where the Cu ions are located in a distorted square pyramid. Magnetization and specific heat measurements reveal the long-range antiferromagnetic order of the Cu$^{2+}$ and/or Sm$^{3+}$ moments for the Sm-sample, with the magnetic specific heat accounting for only 35% of the magnetic entropy. Interestingly, the Eu-sample remains paramagnetic down to the lowest temperature. The high Curie-Weiss temperature of −140 K and magnetic entropy of 3% of the expected value indicates that the system is highly frustrated. We estimated the isothermal entropy change and investigated the magnetocaloric effect for Eu$_2$BaCuO$_5$, and the maximum entropy change detected at a field of 70 kOe at 3 K reaches 5.6 J kg$^{-1}$K$^{−1}$., Published by Frontiers Media, Lausanne

European journal of mineralogy 34(2), 201 - 213 (2022). doi:10.5194/ejm-34-201-2022, The dehydration reaction of phase A + high P clinoenstatite to forsterite + water was experimentally investigated at water-saturated conditions in the pressure range between 7.0 and 10.0 GPa by in situ reversal runs in a multi-anvil press at the synchrotron source of PETRA III in Hamburg. By using closed watertight X-ray transparent Ti capsules, its position is determined by reversal brackets at 8.3 GPa (700–760 ∘C), 8.6 GPa (700–740 ∘C), and 9.8 GPa (750–800 ∘C); thus, the equilibrium of the reaction corresponds ideally to the data reported by Wunder (1998). Optical investigations of the quenched product phases show strong grain coarsening of phase A and clinoenstatite, whereas nucleated forsterite from the breakdown of the aforementioned phases is very fine grained. This corresponds to recent experimental observations that the grain size of phases formed in hydration reactions are significantly larger than those from dehydration reactions.In addition, we performed three time-dependent in situ experiments at 9–10 GPa and 800–870 ∘C and monitored the reaction progress every 10 min to determine the kinetics of the forsterite formation from phase A + high P clinoenstatite. The growth of forsterite at these P–T conditions, already visible after 10 min, confirms the results of the bracketing experiments. However, the reaction is extremely slow, and even after more than 3 h, significant amounts of phase A and high P clinoenstatite are still present. This is in contradiction to other dehydration reactions of former experimental studies, e.g. the fast dehydration of serpentine, which completely dehydrates within 3 h, even at much lower temperatures, closely overstepping serpentine stability.Despite its reaction sluggishness, which would contradict the concept of earthquake initiation, the observed formation of nano-sized forsterite as a dehydration product may still indicate the potential of this reaction to cause mechanical instabilities and, thus, seismicity within cold subduction zones at depths of the Earth's mantle. Additionally, at depths exceeding serpentine dehydration, the phase A + high P/low P clinoenstatite breakdown to forsterite + water might induce geochemical and geophysical processes, including the formation of low-velocity zones within the overlying mantle wedge from the large amounts of fluid liberated by this water line reaction. After the breakdown of antigorite, the assemblage phase A + clinoenstatite might act as a bridge to transport water to larger depths during cold subduction, followed by the formation of other hydrous high P phases., Published by Copernicus Publications, Göttingen

Journal of synchrotron radiation 29(2), 409 - 423 (2022). doi:10.1107/S1600577522001047, Penetrating, high-energy synchrotron X-rays are strongly in demand, particularly for high-pressure research in physics, chemistry, and geosciences and for materials engineering research under less extreme conditions. A new high-energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the end-station P61B. In detail, particular attention is given to the unprecedented high-energy photon flux delivered by the 10 wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world���s first 6-ram, Hall-type LVP called ���Aster-15��� at a synchrotron facility is described for research with synchrotron X-rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy-dispersive X-ray diffraction and radiography techniques are presented., Published by Wiley-Blackwell, [S.l.]

Accepted manuscript of Xie, L., Chanyshev, A., Ishii, T., Bondar, D., Nishida, K., Chen, Z., Bhat, S., Farla, R., Higo, Y., Tange, Y., Su, X., Yan, B., Ma, S., Katsura, T., Simultaneous generation of ultrahigh pressure and temperature to 50 GPa and 3300 K in multi-anvil apparatus, Rev. Sci. Instr., 92, 103902, 2021. https://doi.org/10.1063/5.0059279

The phase relations of iron-rich olivine and its high-pressure polymorphs are important for planetary science and meteoritics because these minerals are the main constituents of terrestrial mantles and meteorites. The olivine–ahrensite binary loop was previously determined by thermochemical calculations in combination with high-pressure experiments; however, the transition pressures contained significant uncertainties. Here we determined the binary loop of the olivine–ahrensite transition in the (Mg,Fe)2SiO4 system at 1740 K in the pressure range of 7.5–11.2 GPa using a multi-anvil apparatus with the pressure determined using in situ X-ray diffraction, compositional analysis of quenched run products, and thermochemical calculation. Based on the determined binary loop, a user-friendly software was developed to calculate pressure from the coexisting olivine and ahrensite compositions. The software is used to estimate the shock conditions of several L6-type chondrites. The obtained olivine–ahrensite phase relations can also be applied for precise in-house multi-anvil pressure calibration at high temperatures., BMBF, H2020 European Research Council http://dx.doi.org/10.13039/100010663, Deutsches Elektronen-Synchrotron (DESY) (4201)