Compressibility of structural modulation waves in the chain compounds BaCoXO (X = As, P): a powder study.

BaCoXO (X = As, P) are built on magnetic 1D units in which strong aperiodic undulations originate from incommensurate structural modulations with large atomic displacive amplitudes perpendicular to the chain directions, resulting in very unique multiferroic properties. High-pressure structural and vibrational properties of both compounds have been investigated by synchrotron X-ray powder diffraction and Raman spectroscopy at room temperature and combined with density functional calculations. A structural phase transition is observed at 1.

Jahn-Teller, polarity, and insulator-to-metal transition in BiMnO3 at high pressure.

The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained thin films. Here we investigate the multiferroic BiMnO3 with its peculiar 6s2 electrons and four interacting mechanisms: electric polarity, octahedra tilts, magnetism, and cooperative Jahn-Teller distortion. We have probed structural transitions under high pressure by synchrotron x-ray diffraction and Raman spectroscopy up to 60 GPa.

Strategies for in situ laser heating in the diamond anvil cell at an X-ray diffraction beamline.

An overview of several innovations regarding in situ laser-heating techniques in the diamond anvil cell at the high-pressure beamline ID27 of the European Synchrotron Radiation Facility is presented. Pyrometry measurements have been adapted to allow simultaneous double-sided temperature measurements with the installation of two additional online laser systems: a CO2 and a pulsed Nd:YAG laser system. This reiteration of laser-heating advancements at ID27 is designed to pave the way for a new generation of state-of-the-art experiments that demand the need for synchrotron diffraction techniques.

Synthesis of tetragonal and orthorhombic polymorphs of Hf3N4 by high-pressure annealing of a prestructured nanocrystalline precursor.

Hf3N4 in nanocrystalline form is produced by solution phase reaction of Hf(NEtMe)4 with ammonia followed by low-temperature pyrolysis in ammonia. Understanding of phase behavior in these systems is important because early transition-metal nitrides with the metal in maximum oxidation state are potential visible light photocatalysts. A combination of synchrotron powder X-ray diffraction and pair distribution function studies has been used to show this phase to have a tetragonally distorted fluorite structure with 1/3 vacancies on the anion sites.

Pressure-induced phase transition(s) in KMnF3 and the importance of the excess volume for phase transitions in perovskite structures.

We report a pressure-dependent investigation of KMnF(3) by x-ray diffraction up to 30 GPa. The results are discussed in the framework of Landau theory and in relation to the isostructural phase transition in SrTiO(3). The phase transition temperature near 186 K in KMnF(3) shifts to room temperature at a critical pressure of P(c) = 3.

Structural investigation of LaAlO3 up to 63 GPa.

We report a high-pressure synchrotron x-ray diffraction on a LaAlO(3) single crystal. The transition from rhombohedral to cubic at 14.8 GPa is confirmed by the loss of the superstructure reflections, whose intensity shows a linear pressure dependence, characteristic of a second-order transition.

The structural behaviour of LaF(3) at high pressures.

We have performed in situ X-ray diffraction, Raman scattering, pseudosymmetry analysis and quantum mechanical atomistic simulations of the structure and behaviour of LaF(3) at high pressure, up to and exceeding the phase transition pressure reported for the I4/mmm structure and Cmma symmetry proposed previously. We observe that the structure of LaF(3)-II is best described as being of anti-Cu(3)Ti-type (oP8, Pmmn, SG59), which is closely related to the I4/mmm structure obtained by simulation, through notional distortion, and is evidently similar to the Cmma symmetry by comparison of published diffraction data. We demonstrate that the models are also related to each other, and can be derived through pseudosymmetry searches.

Raman imaging and Kelvin probe microscopy for the examination of the heterogeneity of doping in polycrystalline boron-doped diamond electrodes.

The issue of the heterogeneity of boron doping in microcrystalline diamond films was addressed by four different methods: micro-Raman spectroscopy and Raman imaging, Kelvin probe force microscopy, conducting atomic force microscopy, and scanning electrochemical microscopy. The samples were commercially available films from Windsor Scientific, with an average boron concentration of about 5 x 10(20) cm(-3). In agreement with previous works, all of the methods showed that the boron uptake was nonuniform across the surface of the electrode.

Biotin grafting on boron-doped diamond.

Grafting of biotin on top of a polycrystalline boron-doped diamond layer was achieved by surface oxidation followed by an esterification reaction and revealed by fluorescently labelled streptavidin.

Opening the high-pressure domain beyond 2 kbar to protein and virus crystallography--technical advance.

The combined use of a diamond anvil cell and ultrashort-wavelength undulator radiation has allowed the collection of high-resolution diffraction data from protein and virus crystals submitted to hydrostatic pressures beyond 2 kbar. Crystals of cubic cowpea mosaic virus (CPMV) can be compressed to at least 3.5 kbar.