Using a synchrotron radiation source and a diamond anvil cell, we measured the pressure dependence of the lattice parameters of a polycrystalline Ti 3 Si 0.5 Ge 0.5 C 2 sample. Up to a pressure of 53 GPa, no phase transformations were observed. As for the isostructural hexagonal Ti 3 SiC 2 , the compressibility along the c axis was greater than along a. The bulk modulus is 183Ϯ4 GPa with a pressure derivative of 3.4Ϯ0.2. This work shows that the replacement of Si by Ge in Ti 3 SiC 2 results in a systematic decrease in the bulk moduli.

A resistively-heated dynamic diamond anvil cell (RHdDAC) setup is presented. The setup enables the dynamic compression of samples at high temperatures by employing a piezoelectric actuator for pressure control and internal heaters for high temperature. The RHdDAC facilitates the precise control of compression rates and was tested in compression experiments at temperatures up to 1400 K and pressures of ∼130 GPa. The mechanical stability of metallic glass gaskets composed of a FeSiB alloy was examined under simultaneous high-pressure/high-temperature conditions. High-temperature dynamic compression experiments on H 2 O ice and (Mg, Fe)O ferropericlase were performed in combination with time-resolved x-ray diffraction measurements to characterize crystal structures and compression behaviors. The employment of high brilliance synchrotron radiation combined with two fast GaAs LAMBDA detectors available at the Extreme Conditions Beamline (P02.2) at PETRA III (DESY) facilitates the collection of data with excellent pressure resolution. The pressure-temperature conditions achievable with the RHdDAC combined with its ability to cover a wide range of compression rates and perform tailored compression paths offers perspectives for a variety of future experiments under extreme conditions.

A laser heating system for samples confined in diamond anvil cells paired with in situ X-ray diffraction measurements at the Extreme Conditions Beamline of PETRA III is presented. The system features two independent laser configurations (on-axis and off-axis of the X-ray path) allowing for a broad range of experiments using different designs of diamond anvil cells. The power of the continuous laser source can be modulated for use in various pulsed laser heating or flash heating applications. An example of such an application is illustrated here on the melting curve of iron at megabar pressures. The optical path of the spectroradiometry measurements is simulated with ray-tracing methods in order to assess the level of present aberrations in the system and the results 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 aspects for accurate temperature measurements are evaluated.

The blueschist to eclogite transition is one of the major geochemical–metamorphic processes typifying the subduction zone, which releases fluids triggering earthquakes and arc volcanism. Although glaucophane is an index hydrous mineral for the blueschist facies, its stability at mantle depths in diverse subduction regimes of contemporary and early Earth has not been experimentally determined. Here, we show that the maximum depth of glaucophane stability increases with decreasing thermal gradients of the subduction system. Along cold subduction geotherm, glaucophane remains stable down ca. 240 km depth, whereas it dehydrates and breaks down at as shallow as ca. 40 km depth under warm subduction geotherm or the Proterozoic tectonic setting. Our results imply that secular cooling of the Earth has extended the stability of glaucophane and consequently enabled the transportation of water into deeper interior of the Earth, suppressing arc magmatism, volcanism, and seismic activities along subduction zones.

The integration of a high energy nanosecond pulse duration laser system in the High Energy Density (HED) instrument of the European XFEL [1] will enable studying atomic structure of materials at extreme pressures and densities. So-called ramp compression [2] using shaped nanosecond laser pulses will allow to generate states of pressure exceeding current limitations of static compression avoiding at the same time steep temperature rise following hugoniot curves. The development and implementation at European XFEL of the required optical laser system with pulse energies in the range beyond 100 J, temporal shaped nanosecond pulses and repetition rates of 0.1 to 10 Hz was recently proposed by an international consortium. Probing of the dynamic, optical laser generated high pressure states will be performed by using high brilliance ultrashort pulse hard x-ray free electron laser (FEL) radiation. In the regime 5 to 25 keV it will be possible to use diffraction, spectroscopy or imaging techniques for investigations of the geometric and electronic structure. The intensity and overall time resolution will enable to perform time-resolved analysis of the evolution of the dynamically compressed systems. Furthermore the high brilliance and coherence of the FEL radiation shall be employed for higher measurement accuracy using spatially resolving techniques avoiding integration over sample volumes of varying excitation and thermo-dynamical properties. Such techniques would become extremely important in case of non-planar and microscopic sample excitation using focused optical laser pulses. [1] for Commonly, structure solution is performed using X-ray diffraction data. However, if single crystals of studied materials are unavailable and/or the alloy contains multiple complex phases -single X-ray diffractometry can not be used and powder X-ray diffraction is powerless due to severe peak overlapping, especially if studied phases are of nano size and peak broadening occurs. In such cases, electron crystallography (EC) emerges as the only tool for structure determination. Although EC was not commonly used for determination of atom positions due to dynamical nature of electron diffraction intensities, the situation has changed when Precession Electron Diffraction (PED), which produces quasi-kinematic intensities, was invented [1]. Using PED method, structures of minerals, complex oxides and zeolites were solved by several research groups. Structures of intermetallics were not solved previously using solely electron diffraction methods. Reason for that is in the nature of intermetallic compounds. Contrarily to zeolites or complex oxides, the atomic distances and angles of intermetallics are not fixed and coordination polyhedra are usually unknown. Thus, structure solution of these compounds is harder to validate and appropriateness of EC methods for their structure solution should be addressed. Present work shows structure solution of several ternary alluminides (as an example of intermetallics) using solely electron crystallography ...