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A novel experimental setup dedicated to the study of liquid and amorphous materials, on the white beam station of the PSICHE' beamline at SOLEIL, is described. The Beer-Lambert absorption method has been developed using a broad-spectrum (white) incident beam for in situ density measurements at extreme conditions of pressure and temperature. This technique has been combined with other existing X-ray techniques (radiographic imaging, tomography and combined angle energy dispersive X-ray diffraction). Such a multi-technical approach offers new possibilities for the characterization of liquid and amorphous materials at high pressure and high temperature. The strength of this approach is illustrated by density measurements of liquid gallium at pressures up to 4 GPa, combining the three independent X-ray techniques (the Beer-Lambert absorption method, tomography and X-ray diffraction). [ABSTRACT FROM AUTHOR]

We have implemented anin situX-ray diffraction analysis method suitable for the determination of pressure–volume–temperature equations of state in the critical case of liquid and amorphous materials over an extended thermodynamic range (T>2000 K andP>40 GPa). This method is versatile, it can be applied to data obtained using various angle-dispersive X-ray diffraction high pressure apparatus and, contrary toin situX-ray absorption techniques, is independent from the sample geometry. Further advantage is the fast data acquisition (between 10 and 300 s integration time). Information on macroscopic bulk properties (density) and local atomic arrangement (pair distribution functiong(r)) can be gathered in parallel. To illustrate the method, we present studies on liquid Fe–S alloys in the Paris Edinburgh press and in laser-heated diamond anvil cell (DAC), and measurements on Ce glass in DAC at room temperature. [ABSTRACT FROM AUTHOR]

• Liquid Fe-S alloys have been investigated by X-ray diffraction in multi-anvil press. • Density has been measured at high pressure and high temperature. • Thermal expansion of liquid Fe-S alloys has been determined up to 7 GPa and 2200 K. • Top-down crystallization common in Fe-FeS cores of planetesimals and small planets. Local structure and density of liquid Fe-S alloys at high pressure have been determined in situ by combined angle and energy dispersive X-ray diffraction experiments in a multi-anvil apparatus, covering a large temperature and compositional range. Precise density measurements collected for increasing temperature allowed us to directly derive the thermal expansion coefficients for liquid Fe-S alloys as a function of composition. In turn, thermal expansion has been used to refine thermodynamic models and to address the crystallization regime of telluric planetary cores by comparing the adiabatic temperature gradient and the slope of the liquidus in the Fe-FeS system. For Fe-S cores of asteroids and small planetesimals, top-down solidification is the dominant scenario as the compositional domain for which the slope of the liquidus is greater than the adiabatic gradient is limited to a narrow portion on the Fe-rich side. However, bottom-up growth of the inner core is expected for S-poor cases, with this compositional domain expanding to more S-rich compositions with increasing pressure (size of the planetary body). In particular, bottom-up crystallization cannot be excluded for the Moon and Ganymede. [ABSTRACT FROM AUTHOR]

Abstract: High-pressure, high-temperature in situ X-ray diffraction has been measured in liquid iron alloys (Fe–5wt% Ni–12wt% S and Fe–5wt% Ni–15wt% Si) up to 94GPa and 3200K in laser-heated diamond anvil cells. From the analysis of the X-ray diffuse scattering signal of the metallic liquids, we determined density and bulk modulus of the two liquid alloys. Comparison with a reference Earth model indicates that a core composition containing 6% of sulfur and 2% of silicon by weight would best match the geophysical data. Models with 2.5% of sulfur and 4–5% of silicon are still consistent with geophysical constraints whereas silicon only compositions are not. These results suggest only moderate depletion of sulfur in the bulk Earth. [Copyright &y& Elsevier]