Temperature-induced phase transition in phlogopite revealed by Raman spectroscopy

Raman study of a natural hydrous phlogopite was carried out at temperatures up to 500 °C for the first time. Evolution of four well-resolved Raman modes at wavenumbers 196, 278, 322, and 682 cm⁻¹ was followed in detail with temperature increase. The analysis of data reveals linear decrease of vibrational wavenumbers in the studied temperature range, with small but experimentally significant discontinuities occurring at a temperature of 365±15 °C. Although the overall appearance of Raman spectra remains intact on crossing this temperature, the presence of discontinuities, as well as a marked difference between Gruneisen parameters calculated for high- and low-temperature ranges, signifies the presence of a temperature-induced phase transformation. By combining and correlating the results of the present Raman study with the high-temperature X-ray work performed by Tutti et al. [High-temperature study and thermal expansion of phlogopite, Phys. Chem. Miner. 27 (2000) 599-603] we arrive at the interpretation of a temperature-induced structural phase transformation in phlogopite without a significant symmetry change, with an underlying microscopic mechanism involving deformation of Mg octahedra and rotation of tetrahedral grid from ditrigonal toward hexagonal at the transition temperature.     

MAX IV is Ready to Make the Invisible Visible

In a ceremony held on June 21, the brightest day of the year in the northern hemisphere, Swedish Prime Minister Stefan Löfven and H.M. King Carl XVI Gustaf, together with Director Christoph Quitmann, inaugurated MAX IV Laboratory in the presence of about 500 staff, funders, stakeholders, and guests from all over the world.     

MAX IV Facility Update: A Pictorial Essay

At MAX IV in Lund, Sweden, commissioning of the linac is ongoing, and a few big milestones have been passed. Electrons have been transported through the first bunch compressor and are now accelerated up to around 1 GeV. They should reach the first transfer line leading to the 1.5 GeV ring shortly. During the fall of 2014, the photo cathode gun was started up and laser electrons were measured. As soon as the electrons from the thermionic gun have reached 3 GeV and are ready for injection into the 3 GeV storage ring, the main focus of commissioning will turn to the photo gun, and high brightness pulses for the Short Pulse Facility. Conditioning of the linac leading up 1.5 GeV is completed, the rest of the structure has been baked, and was expected at press time to reach full conditioning at the end of November 2014 (Figures 1–4).     

In situ X-Ray study of thermal expansion and phase transition of iron at multimegabar pressure

The density of varepsilon-iron has been calculated at pressures and temperatures up to 300 GPa and 1300 K, respectively. We observe varepsilon to beta phase transition at pressures between 135 and 300 GPa and temperature above 1350 K; the pattern can be interpreted in terms of double hexagonal close-packed structure. The density calculated at high pressure and temperature (330-360 GPa and 5000-7000 K) closely matches with preliminary reference Earth model density, thereby imposing constraint on the composition of the Earth's inner core.