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Precise structure analyses of advanced materials under pressure were performed using each advantage of X-ray absorption fine structure (XAFS) and diffraction methods. Measurements were performed in-situ under pressure and temperature using a large-volume multi-anvil pressure apparatus and synchrotron radiation. XAFS spectra are useful for phase study under high temperature and high pressure. The XAFS Debye Waller factor provides anharmonic effective pair potential with a pressure-dependent and temperature-independent shape. The phonon energies and anharmonicity are affected largely by the change in local structure and bonding character. [ABSTRACT FROM AUTHOR]

Abstract: After a brief review of recent studies under high-pressure and high-temperature conditions using large-volume multi-anvil presses in the SPring-8 synchrotron radiation facility, new data of the pressure dependence of the structure factor for silica glass under high pressure is presented. The position of the first sharp diffraction peak in the structure factor of silica glass moved to a higher momentum transfer as pressure is increased. It moves in the same direction as temperature is increased at 8.5GPa. The intermediate-range structure relaxes to a denser one. On decompression at room temperature, the position of the first sharp diffraction peak showed a large hysteresis. A smaller hysteresis was observed for a sample without a heat treatment at high pressure. A mechanism of permanent densification of silica glass by the heat treatment under high pressure is discussed. [Copyright &y& Elsevier]

The article discusses the highlights of the 2012 meeting of the International Union of Crystallography Commission on High Pressure held in conjunction with the International Symposium of the Quantum Beam Science Directorate of the Japan Atomic Energy Agency held from September 23 to 27. Ten scientific sessions were organized on topics including crystal structures, phase transitions, magnetic and electronic phenomena at high pressure and materials science.

Abstract: The density of hydrous peridotite magma containing 5wt.% H2O was measured at pressures and temperatures up to 4.3GPa and 2073K, respectively, using the X-ray absorption method. A fit of pressure–density–temperature data to the high-temperature Birch–Murnaghan equation of state yields isothermal bulk modulus K T =8.8±1.9GPa, its pressure derivative K′=9.9±3.6 and the temperature derivative of the bulk modulus (∂K T /∂T) P =−0.0022±0.0015GPa/K at 1773K. The small bulk modulus of the hydrous peridotite magma compared with that of the dry peridotite magma reflects the effect of water, which is more compressible than the silicate melt. The partial molar volume of H2O in magma under high pressure conditions was calculated and fitted using the Vinet equation of state. The isothermal bulk modulus was K T =2.4±1.0GPa, and its pressure derivative was K′=5.7±1.5 at 1973K. [Copyright &y& Elsevier]