A. Bosak

Phonon dispersion of graphite by inelastic x-ray scattering

We present the full in-plane phonon dispersion of graphite obtained from inelastic x-ray scattering, including the optical and acoustic branches, as well as the mid-frequency range between the

Spin crossover in ferropericlase at high pressure: a seismologically transparent transition?

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Inelastic X-ray scattering in YBa2Cu3O6.6 reveals giant phonon anomalies and elastic central peak due to charge-density-wave formation

and

High‐Resolution Transmission X‐ray Microscopy: A New Tool for Mesoscopic Materials

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Suppression of thermal conductivity by rattling modes in thermoelectric sodium cobaltate

points in the Brillouin zone, where experimental data have been unavailable so far. The existence of a Kohn anomaly at the

Elasticity of hexagonal boron nitride: Inelastic x-ray scattering measurements

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Diffuse scattering in relaxor ferroelectrics: true three-dimensional mapping, experimental artefacts and modelling

point is further supported. We fit a fifth-nearest neighbour force-constants model to the experimental data, making improved force-constants calculations of the phonon dispersion in both graphite and carbon nanotubes available.

Phonon surface mapping of graphite: Disentangling quasi-degenerate phonon dispersions

An iron spin transition has no effect on the seismologic properties of lower-mantle minerals. Seismic discontinuities in Earth typically arise from structural, chemical, or temperature variations with increasing depth. The pressure-induced iron spin state transition in the lower mantle may influence seismic wave velocities by changing the elasticity of iron-bearing minerals, but no seismological evidence of an anomaly exists. Inelastic x-ray scattering measurements on (Mg0.83Fe0.17)O-ferropericlase at pressures across the spin transition show effects limited to the only shear moduli of the elastic tensor. This explains the absence of deviation in the aggregate seismic velocities and, thus, the lack of a one-dimensional seismic signature of the spin crossover. The spin state transition does, however, influence shear anisotropy of ferropericlase and should contribute to the seismic shear wave anisotropy of the lower mantle.

Structural Heterogeneity and Diffuse Scattering in Morphotropic Lead Zirconate-Titanate Single Crystals

1 Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart, Germany 2 European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France 3 CNR-SPIN, CNISM and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy 4 Institut für Festkörperphysik, Karlsruher Institut für Technologie (KIT), P.O.B. 3640, D-76021 Karlsruhe, Germany

Strong anharmonicity induces quantum melting of charge density wave in 2H-NbSe

The whole is sometimes more than the sum of its parts. Certainly it is true for ordered mesoscopic materials, when the assembly of particles acquires properties which are not the intrinsic ones of the constituent particles. One of the best illustrative examples is the case of photonic crystals – attractive optical materials for controlling and manipulating the fl ow of light. Since the appearance of seminal papers in 1987 the number of research papers devoted to the subject, began to grow exponentially. [ 1–2 ] Three-dimensional photonic crystals offer additional features compared to 1D (gratings, multilayers) and 2D cases, possibly leading to new device concepts (e.g., for optical computing), but manufacturing problems are still far from being solved. While 2D structures could be created by techniques adapted from semiconductor industry, this is less obvious for the 3D case, and as an alternative self-assembly approaches are considered to have a great potential. [ 3 ] The effi ciency of the latter approach is demonstrated long ago by the very existence of prototypical photonic crystals – gem opals. In the case of photonic materials, the crystalline structure of individual subunits is practically of no relevance. The target design properties are not only defi ned by the average mesoscopic structure, but by its specifi c realization, including random or correlated defects (non-monodisperse subunits, vacancies, dislocations, stacking faults, etc.). The mesoscale can be probed by imaging-related or diffraction-related methods. The fi rst family of techniques was exclusively limited to surface imaging, namely to scanning electron microscopy and a replica-technique variety of transmission electron microscopy. [ 4–6 ]