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The structure of a 4,4′-dinitrobiphenyl and biphenyl 3 : 1 composite cocrystal is presented in (3 + 1)D superspace.

Iron phosphate materials have attracted a lot of attention due to their potential as cathode materials for lithium-ion rechargeable batteries. It has been shown that lithium insertion or extraction depends on the Fe mixed valence and reduction or oxidation of the Fe ions' valences. In this paper, we report a new synthesis method for the Fe

The high-Z′ (Z′ = 7) structure of glycyl-l-valine has been redetermined at 298 K, using synchrotron radiation and exploiting the superspace approach. The analysis of the diffraction data reveals th...

The nuclear and magnetic structures of Mn

14th International Conference on Synchrotron Radiation Instrumentation, (SRI 2021), Hamburg, Germany, 28 Mar 2022 - 1 Apr 2022; Journal of physics / Conference Series 2380(1), 012098 (2022). doi:10.1088/1742-6596/2380/1/012098, Alternative to the traditional analog methods, several digital data preprocessing, shaping and postprocessing techniques have been investigated for the improvement in energy resolution of energy dispersive x-rays detectors. Initial experimental results show that by preprocessing the data, better energy resolution can be obtained at shorter shaping times; thus, it will allow good energy and time resolution at high count rates., Published by IOP Publ., Bristol

Materials 15(22), 8059 (2022). doi:10.3390/ma15228059, Iron phosphate materials have attracted a lot of attention due to their potential as cathode materials for lithium-ion rechargeable batteries. It has been shown that lithium insertion or extraction depends on the Fe mixed valence and reduction or oxidation of the Fe ions’ valences. In this paper, we report a new synthesis method for the Fe$_3$(PO$_3$OH)$_4$(H$_2$O)$_4$ mixed valence iron phosphate. In addition, we perform temperature-dependent measurements of structural and physical properties in order to obtain an understanding of electronic–structural interplay in this compound. Scanning electron microscope images show needle-like single crystals of 50 μm to 200 μm length which are stable up to approximately 200 °C, as revealed by thermogravimetric analysis. The crystal structure of Fe$_3$(PO$_3$OH)$_4$(H$_2$O)$_4$ single crystals has been determined in the temperature range of 90 K to 470 K. A monoclinic isostructural phase transition was found at ~213 K, with unit cell volume doubling in the low temperature phase. While the local environment of the Fe$^{2+}$ ions does not change significantly across the structural phase transition, small antiphase rotations occur for the Fe$^{3+}$ octahedra, implying some kind of electronic order. These results are corroborated by first principle calculations within density functional theory, which also point to ordering of the electronic degrees of freedom across the transition. The structural phase transition is confirmed by specific heat measurements. Moreover, hints of 3D antiferromagnetic ordering appear below ~11 K in the magnetic susceptibility measurements. Room temperature visible light absorption is consistent with the Fe$^{2+}$/Fe$^ {3+}$ mixed valence., Published by MDPI, Basel

Advanced functional materials 32(38), 2202226 (2022). doi:10.1002/adfm.202202226, Different SrTiO$_3$ thin films are investigated to unravel the nature of ultra-low conductivities recently found in SrTiO$_3$ films prepared by pulsed laser deposition. Impedance spectroscopy reveals electronically pseudo-intrinsic conductivities for a broad range of different dopants (Fe, Al, Ni) and partly high dopant concentrations up to several percent. Using inductively-coupled plasma optical emission spectroscopy and reciprocal space mapping, a severe Sr deficiency is found and positron annihilation lifetime spectroscopy revealed Sr vacancies as predominant point defects. From synchrotron-based X-ray standing wave and X-ray absorption spectroscopy measurements, a change in site occupation is deduced for Fe-doped SrTiO$_3$ films, accompanied by a change in the dopant type. Based on these experiments, a model is deduced, which explains the almost ubiquitous pseudo-intrinsic conductivity of these films. Sr deficiency is suggested as key driver by introducing Sr vacancies and causing site changes (Fe$_{Sr}$ and Ti$_{Sr}$) to accommodate nonstoichiometry. Sr vacancies act as mid-gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably Ti$_{Sr}^{\bullet\bullet}$) are present. Defect chemical modeling revealed that such a Fermi level pinning also causes a self-limitation of the Ti site change and leads to a very robust pseudo-intrinsic situation, irrespective of Sr/Ti ratios and doping., Published by Wiley-VCH, Weinheim

The three-dimensional charge density wave (CDW) compound ${\mathrm{Lu}}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$ undergoes a first-order CDW phase transition at around 200 K. An atypical CDW state is found, that is characterized by an incommensurate CDW with $\mathbf{q}=[0.2499(3),0.4843(4),0.2386(2)]$ at 60 K, and a large orthorhombic-to-triclinic lattice distortion with $\ensuremath{\beta}=91.945{(2)}^{\ensuremath{\circ}}$. We present the modulated crystal structure of the incommensurate CDW state. Structural analysis shows that the CDW resides on the zigzag chains of iridium atoms along $\mathbf{c}$. The structural distortions are completely similar between nonmagnetic ${\mathrm{Lu}}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$ and previously studied isostructural magnetic ${\mathrm{Er}}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$ with the small differences explained by the different values of the atomic radii of Lu and Er. Such a similarity is unique to ${R}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$ $(R=\mathrm{rare}\phantom{\rule{0.28em}{0ex}}\mathrm{earth})$. It differs from, for example, the rare-earth CDW compounds ${R}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}$ for which ${\mathrm{Lu}}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}$ and ${\mathrm{Er}}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}$ possess entirely different CDW states. We argue that the mechanism of CDW formation, thus, is different for ${R}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$ and ${R}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}$.

Structural analysis of spin frustrated Ho

The first-order charge density wave (CDW) phase transition of ${\mathrm{Er}}_{2}{\mathrm{Ir}}_{3}{\mathrm{Si}}_{5}$ is characterized by a crystal structure analysis, and electrical resistivity, magnetic susceptibility and specific heat measurements. The incommensurate CDW is accompanied by a strong lattice distortion, from which it is shown that the CDW resides on zigzag chains of iridium atoms. The CDW transition affects the magnitude of the local magnetic moments on ${\mathrm{Er}}^{3+}$, implying strong coupling between CDW and magnetism. This could account for the observation that magnetic order is suppressed down to at least 0.1 K in the high-quality single crystal presently studied. Any disorder in the crystallinity, as in ceramic material, broadens and suppresses the CDW transition, while magnetic order appears at 2.1 K.

We present the temperature dependence of the electrical resistivity, the magnetic susceptibility, and the specific heat of a high-quality single crystal of ${\mathrm{La}}_{3}{\mathrm{Co}}_{4}{\mathrm{Sn}}_{13}$. As opposed to earlier reports on this system, these bulk properties exhibit clear anomalies at the phase transition at ${T}^{*}=151(1)$ K, while the present data confirm the second-order character of this transition. X-ray diffraction with synchrotron radiation is used to solve the fourfold superstructure in space group $I{2}_{1}3$ as it exists below ${T}^{*}$ in the charge-density-wave (CDW) state of ${\mathrm{La}}_{3}{\mathrm{Co}}_{4}{\mathrm{Sn}}_{13}$. Unlike conventional CDW systems, we have observed hysteresis between the zero-field-cooled and field-cooled magnetization below the CDW transition. This discrepancy can be attributed to a possible magnetic instability arising out of correlations of Co in the lattice, developing at the CDW transition. The crystal structure shows that any modifications of the electronic state of Co might be due to modified binding characteristics of the Sn atoms comprising the trigonal prismatic coordination of Co, while the coordination of Co itself is hardly changed at the phase transition. The superconducting transition is observed at ${T}_{\text{sc}}=2.85(2)$ K. The superconducting energy gap is estimated as 5 K on the basis of the specific heat measured down to 0.1 K. These results suggest that ${\mathrm{La}}_{3}{\mathrm{Co}}_{4}{\mathrm{Sn}}_{13}$ is a conventional weak-electron-phonon-coupling superconductor.

The three-dimensional charge density wave (CDW) compound ${\mathrm{CuV}}_{2}{\mathrm{S}}_{4}$ is known to undergo phase transitions at $\ensuremath{\sim}91$ and $\ensuremath{\sim}50\phantom{\rule{4pt}{0ex}}\mathrm{K}$. Employing single-crystal x-ray diffraction on an annealed crystal, we confirm the formation of an incommensurate CDW at ${T}_{\text{CDW}}\ensuremath{\approx}91\phantom{\rule{4pt}{0ex}}\mathrm{K}$, and we establish the nature of the transition at ${T}_{\text{lock-in}}\ensuremath{\approx}50\phantom{\rule{4pt}{0ex}}\mathrm{K}$ as a lock-in transition toward a threefold superstructure. As-grown crystals develop the same incommensurate CDW as the annealed crystal does, but they fail to go through the lock-in transition. Instead, the length of the modulation wave vector continues to decrease down to low temperatures in as-grown crystals. These findings are corroborated by distinct temperature dependencies of the electrical resistivity, magnetic susceptibility, and specific heat measured on as-grown and annealed crystals. A superspace model for the crystal structure of the incommensurate CDW suggests that the formation of extended vanadium clusters is at the origin of the CDW. In the lock-in phase, short and long V-V distances persist, but clusters now percolate the entire crystal. The lowering toward orthorhombic symmetry appears to be responsible for the precise pattern of short and long V-V distances. However, the orthorhombic lattice distortion is nearly zero for the annealed crystal, while it is visible for the as-grown material, again suggesting the role of lattice defects in the latter.

Physical review letters 122(12), 123608 (2019). doi:10.1103/PhysRevLett.122.123608, By embedding a thin layer of tantalum in an x-ray cavity, we observe a change in the spectral characteristics of an inner-shell transition of the metal. The interaction between the cavity mode vacuum and the $L_{III}$-edge transition is enhanced, permitting the observation of the collective Lamb shift, superradiance, and a Fano-like cavity-resonance interference effect. This experiment demonstrates the feasibility of cavity quantum electrodynamics with electronic resonances in the x-ray range with applications to manipulating and probing the electronic structure of condensed matter with high-resolution x-ray spectroscopy in an x-ray cavity setting., Published by APS, College Park, Md.

Acta crystallographica / A 77(a2), C179 (2021). doi:10.1107/S0108767321095039, Published by Blackwell, Oxford [u.a.]

Structural analysis of spin frustrated Ho2Ge x Ti2-x O7 (x = 0, 0.1, 0.15 & 0.25) pyrochlore oxides has been performed using high resolution x-ray diffraction pattern and low temperature synchrotron x-ray diffraction pattern. The effect of positive chemical pressure on the spin dynamics of Ho2Ge x Ti2-x O7 has been analysed through the study of static (M-T and M-H; magnetisation against temperature & magnetisation against magnetic field) and dynamical (ac susceptibility) magnetic measurements. In lower temperature regime (∼2 K), such systems are predominantly governed by competing exchange (J nn) and dipolar (D nn) magnetic interactions. Magnetic measurements indicate that the application of increased chemical pressure in Ho2Ti2O7 matrix propels the system towards diminished ferromagnetic interaction. Dipolar coupling constant remains almost unchanged but Curie-Weiss temperature (θ cw) reduces to -0.04 K from 0.33 K (for an applied magnetic field; H = 100 Oe) with increasing x in Ho2Ge x Ti2-x O7. Positive chemical pressure establishes the dominance of Ho-Ho antiferromagnetic interaction J nn over dipolar interaction D nn. Spin relaxation feature corresponding to thermally activated single ion freezing (T s∼15 K) is shifted towards lower temperature. This chemical pressure-driven T s shift is ascribed to the alteration in crystal field effect, which reduces the activation energy for singe ion spin freezing. The reduction in the activation energy indicates crystal field-phonon coupling in Ho2Ge x Ti2-x O7 system. The robustness in spin ice freezing (second spin relaxation feature in ac susceptibility curve) remains unaffected with increasingly chemical pressure. This spin freezing ('2 in-2 out' spin arrangement in tetrahedra) is related to quantum tunnelling phenomenon, at T ice ∼ 2 K. It indicates that majority of spins still follows the 'ice rule' in Ho2Ge x Ti2-x O7 even after the application of chemical pressure.

Lithium reactive hydride composite 2LiBH4 + MgH2 (Li-RHC) has been lately investigated owing to its potential as hydrogen storage medium for mobile applications. However, the main problem associated with this material is its sluggish kinetic behavior. Thus, aiming to improve the kinetic properties, in the present work the effect of the addition of Fe to Li-RHC is investigated. The addition of Fe lowers the starting decomposition temperature of Li-RHC about 30 °C and leads to a considerably faster isothermal dehydrogenation rate during the first hydrogen sorption cycle. Upon hydrogenation, MgH2 and LiBH4 are formed whereas Fe appears not to take part in any reaction. Upon the first dehydrogenation, the formation of nanocrystalline, well distributed FeB reduces the overall hydrogen storage capacity of the system. Throughout cycling, the agglomeration of FeB particles causes a kinetic deterioration. An analysis of the hydrogen kinetic mechanism during cycling shows that the hydrogenation and dehydrogenation behavior is influenced by the activity of FeB as heterogeneous nucleation center for MgB2 and its non-homogenous distribution in the Li-RHC matrix. Fil: Puszkiel, Julián Atilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Gennari, Fabiana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro Atómico Bariloche; Argentina Fil: Arneodo Larochette, Pierre Paul. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro Atómico Bariloche; Argentina Fil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Vainio, U.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; . Deutsches Elektronen-Synchrotron; Alemania Fil: Karimi, F.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Pranzas, P. K.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro Atómico Bariloche; Argentina Fil: Pistidda, C.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Jepsen, J.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Tolkiehn, M.. Deutsches Elektronen-Synchrotron; Alemania Fil: Welter, E.. Deutsches Elektronen-Synchrotron; Alemania Fil: Klassen, T.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Bellosta Von Colbe, J.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Dornheim, M.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh

In the present work we focus the attention on the phase structural transformations occurring upon the desorption process of the LiBH 4 + LiAlH 4 system. This study is conducted by means of manometric–calorimetric, in situ Synchrotron Radiation Powder X-ray Diffraction (SR-PXD) and ex situ Solid State Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) measurements. The desorption reaction is characterized by two main dehydrogenation steps starting at 320 and 380 °C, respectively. The first step corresponds to the decomposition of LiAlH 4 into Al and H 2 via the formation of Li 3 AlH 6 whereas the second one refers to the dehydrogenation of LiBH 4 (molten state). In the range 328–380 °C, the molten LiBH 4 reacts with metallic Al releasing hydrogen and forming an unidentified phase which appears to be an important intermediate for the desorption mechanism of LiBH 4 –Al-based systems. Interestingly, NMR studies indicate that the unknown intermediate is stable up to 400 °C and it is mainly composed of Li, B, Al and H. In addition, the NMR measurements of the annealed powders (400 °C) confirm that the desorption reaction of the LiBH 4 + Al system proceeds via an amorphous boron compound.

Designing safe, compact and high capacity hydrogen storage systems is the key step towards introducing a pollutant free hydrogen technology into a broad field of applications. Due to the chemical bonds of hydrogen-metal atoms, metal hydrides provide high energy density in safe hydrogen storage media. Reactive hydride composites (RHCs) are a promising class of high capacity solid state hydrogen storage systems. Ca(BH4)2 + MgH2 with a hydrogen content of 8.4 wt% is one of the most promising members of the RHCs. However, its relatively high desorption temperature of ∼350 °C is a major drawback to meeting the requirements for practical application. In this work, by using NbF5 as an additive, the dehydrogenation temperature of this RHC was significantly decreased. To elucidate the role of NbF5 in enhancing the desorption properties of the Ca(BH4)2 + MgH2 (Ca-RHC), a comprehensive investigation was carried out via manometric measurements, mass spectrometry, Differential Scanning Calorimetry (DSC), in situ Synchrotron Radiation-Powder X-ray Diffraction (SR-PXD), X-ray Absorption Spectroscopy (XAS), Anomalous Small-Angle X-ray Scattering (ASAXS), Scanning and Transmission Electron Microscopy (SEM, TEM) and Nuclear Magnetic Resonance (NMR) techniques. Fil: Karimi, Fahim. Helmholtz-zentrum Geesthacht; Alemania Fil: Klaus Pranzas, P.. Helmholtz-zentrum Geesthacht; Alemania Fil: Pistidda, Claudio. Helmholtz-zentrum Geesthacht; Alemania Fil: Puszkiel, Julián Atilio. Helmholtz-zentrum Geesthacht; Alemania. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Milanese, Chiara. Universita Degli Studi Di Pavia; Italia Fil: Vainio, Ulla. Helmholtz-zentrum Geesthacht; Alemania Fil: Paskevicius, Mark. Curtin University; Australia Fil: Emmler, Thomas. Helmholtz-zentrum Geesthacht; Alemania Fil: Santoru, Antonio. Helmholtz-zentrum Geesthacht; Alemania Fil: Utke, Rapee. Helmholtz-zentrum Geesthacht; Alemania. Suranaree University of Technology; Tailandia Fil: Tolkiehn, Martin. No especifíca; Fil: Minella, Christian B.. Helmholtz-zentrum Geesthacht; Alemania Fil: Chaudhary, Anna Lisa. Helmholtz-zentrum Geesthacht; Alemania Fil: Boerries, Stefan. Helmholtz-zentrum Geesthacht; Alemania Fil: Buckley, Craig E.. Curtin University; Australia Fil: Enzo, Stefano. University of Sassari; Italia Fil: Schreyer, Andreas. Helmholtz-zentrum Geesthacht; Alemania Fil: Klassen, Thomas. Helmholtz-zentrum Geesthacht; Alemania Fil: Dornheim, Martin. Helmholtz-zentrum Geesthacht; Alemania

Hydrogen sorption properties of the LiH–MgB2 system doped with TiCl3 were investigated with respect to milling conditions (milling times, ball to powder (BTP) ratios, rotation velocities and degrees of filling) to form the reactive hydride composite (RHC) LiBH4–MgH2. A heuristic model was applied to approximate the energy transfer from the mill to the powders. These results were linked to experimentally obtained quantities such as crystallite size, specific surface area (SSA) and homogeneity of the samples, using X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method and scanning electron microscopy (SEM), respectively. The results show that at approximately 20 kJ g1 there are no further benefits to the system with an increase in energy transfer. This optimum energy transfer value indicates that a plateau was reached for MgB2 crystallite size therefore the there was also no improvement of reaction kinetics due to no change in crystallite size. Therefore, this study shows that an optimum energy transfer value was reached for the LiH–MgB2 system doped with TiCl3.

We investigated antidot lattices with Andreev reflecting boundaries both in experiment and theory. The samples consist of arrays of niobium-filled antidots in an InAs-based heterostructure. The quality of the Nb–InAs contact could be controlled by an in situ Ar+ sputter cleaning step. In samples with a high transparency contact, we find a strong reduction of the resistance around B=0 and a suppression of the commensurability peaks. These observations can be explained in a classical Kubo approach by including Andreev reflection and assuming a magnetic-field-dependent Andreev reflection probability.

Mge10 mol% LiBH4 composite plus small amounts of FeF3 is investigated in the present work. The presence of LiBH4 during the milling process noticeably modifies the size and morphology of the Mg agglomerates, leading to faster hydrogenation and reaching almost the theoretical hydrogen capacity owing to enhanced hydrogen diffusion mechanism. However, the dehydrogenation of the system at low temperatures (300 C) is still slow. Thus, FeF3 addition is proposed to improve the dehydrogenation kinetic behavior. From experimental results, it is found that the presence of FeF3 results in an additional size reduction of the Mg agglomerates between ~10 and ~100 mm and the formation of stable phases such as MgF2, LiF and FeB. The FeB species might have a catalytic effect upon the MgH2 decomposition. As a further result of the FeF3 addition, the Mge10 mol%LiBH4e5 mol% FeF3 material shows improved dehydrogenation properties: reduced dehydrogenation activation energy, faster hydrogen desorption rate and reversible hydrogen capacities of about 5 wt% at 275 C. Fil: Puszkiel, Julián Atilio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Centre for Materials and Coastal Research; Alemania Fil: Gennari, Fabiana Cristina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Arneodo Larochette, Pierre Paul. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Karimi, Fahim. Centre for Materials and Coastal Research; Alemania Fil: Pistidda, Claudio. Centre for Materials and Coastal Research; Alemania Fil: Gosalawit e Utke, Rapee. Centre for Materials and Coastal Research; Alemania. Institute of Science, Suranaree University of Technology; Tailandia Fil: Jepsen, Julian. Centre for Materials and Coastal Research; Alemania Fil: Jensen, Torben R.. University of Aarhus; Dinamarca Fil: Gundlach, Carsten. University of Aarhus; Dinamarca Fil: Tolkiehn, Martin. HASYLAB at DES; Alemania Fil: Bellosta von Colbe, José. Centre for Materials and Coastal Research; Alemania Fil: Klassen, Thomas. Centre for Materials and Coastal Research; Alemania Fil: Dornheim, Martin. Centre for Materials and Coastal Research; Alemania

In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) technique is a powerful tool to gain a deeper understanding of reaction mechanisms in crystalline materials. In this paper, the implementation of a new in-situ SR-PXD cell for solid–gas reactions is described in detail. The cell allows performing measurements in a range of pressure which goes from light vacuum (10−2 bar) up to 200 bar and temperatures from room temperature up to 550 °C. The high precision, with which pressure and temperature are measured, enables to estimate the thermodynamic properties of the observed changes in the crystal structure and phase transformations.

In this work the effect of a partial replacement of CaH2 with CaF2 on the sorption properties of the system CaH2 + MgB2 has been studied. The first five hydrogen absorption and four desorption reactions of the CaH2 + MgB2 and 3CaH(2) + CaF2 + 4MgB(2) systems were investigated by means of volumetric measurements, high-pressure differential scanning calorimetric technique (HP-DSC), B-11 and 19F MAS NMR spectroscopy, and in situ synchrotron radiation powder X-ray diffraction (SR-PXD). It was observed that already during the mixing of the reactants formation of a nonstoichiometric CaF2-xHx solid solution takes place. Formation of the CaF2-xHx solid solution sensibly affects the overall hydrogen sorption reactions of the system CaH2 + MgB2.

In this work the effect of the ratio of starting reactants on the hydrogen absorption reaction of the system xNaH + MgB2 is investigated. At a constant hydrogen pressure of 50 bar, depending on the amount of NaH present in the system NaH + MgB2, different hydrogen absorption behaviors are observed. For two system compositions: NaH + MgB2 and 0.5NaH + MgB2, the formation of NaBH4 and MgH2 as only crystalline hydrogenation products is achieved. The relation between the ratio of the starting reactants and the obtained hydrogenation products is discussed in detail.

We compare results from single crystal X-ray diffraction and FTIR spectroscopy to elucidate the nature of hydrogen bonding in β-9-anthracene carboxylic acid (β-9AC, C(15)H(10)O(2)). The crystallographic studies indicate a disorder for the protons in the cyclic hydrogen bond. This disorder allows the determination of the energy difference between two proton sites along the hydrogen bond. The temperature dependent Fourier transform infrared spectroscopy (FTIR) underpins the crystallographic results. The combination of both methods allows the estimation of a one-dimensional potential curve describing the OH-stretching motion. The dynamical properties of the proton transfer along the hydrogen bond are extracted from this potential. The work presented here has profound implication on future studies of photochemical dynamics of crystalline β-9AC, which can deliver a deeper understanding of the mechanism of photochemical driven molecular machines and the optical and electronic properties of molecular organic semiconductors.

It has been proposed that radiation from free electron laser (FEL) at Hamburg (FLASH) can be used for ultrafast time-resolved x-ray diffraction experiments based on the near-infrared (NIR) pump/FEL probe scheme. Here, investigation probing the ultrafast structural dynamics of periodic nano-crystalline organic matter (silver behenate) with such a scheme is reported. Excitation with a femtosecond NIR laser leads to an ultrafast lattice modification which time evolution has been studied through the scattering of vacuum ultraviolet FEL pulses. The found effect last for 6 ps and underpins the possibility for studying nanoperiodic dynamics down to the FEL source time resolution. Furthermore, the possibility of extending the use of silver behenate (AgBh) as a wavelength and temporal calibration tool for experiments with soft x-ray/FEL sources is suggested.

High-pressure behaviours of isomorphous HoMn(2)O(5) and BiMn(2)O(5) (Pbam, Z = 4) were studied, using Raman spectroscopy and single-crystal x-ray diffraction, with the samples in diamond anvil cells pressurized to 10.09 GPa and 8.54 GPa, respectively, at room temperature. No phase transition was detected in either material. The two manganates are most compressible along the a axis with the lattice contractions along the b and c directions nearly the same. Their P-V data fitted with the second-order Birch-Murnaghan equation of state (B' = 4.0) give the bulk moduli B(0) = 138(2) GPa for BiMn(2)O(5) and B(0) = 173(3) GPa for HoMn(2)O(5). The difference in bulk moduli results from BiMn(2)O(5) being more compressible than HoMn(2)O(5) along the a axis. Our study shows that the Mn-O frameworks in isomorphous RMn(2)O(5) compounds (R = Bi and rare earth) are not rigid at high pressures, but rather adapt to the behaviour of the coordination spheres around the R atoms. Bond valence calculations indicate that the pressure-induced charge transfers between the two Mn sites have different characters for the two compounds.

In this Letter, we report the pioneering use of free electron laser radiation for the investigation of periodic crystalline structures. The diffraction properties of silver behenate single nanocrystals (5.8 nm periodicity) with the dimensions of $20\text{ }\text{ }\mathrm{nm}\ifmmode\times\else\texttimes\fi{}20\text{ }\text{ }\mathrm{nm}\ifmmode\times\else\texttimes\fi{}20\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ and as powder with grain sizes smaller than 200 nm were investigated with 8 nm free electron laser radiation in single-shot modus with 30 fs long free electron laser pulses. This work emphasizes the possibility of using soft x-ray free electron laser radiation for these crystallographic studies on a nanometer scale.

An Andreev billiard was realized in an array of niobium filled antidots in a high-mobility InAs/AlGaSb heterostructure. Below the critical temperature T_C of the Nb dots we observe a strong reduction of the resistance around B=0 and a suppression of the commensurability peaks, which are usually found in antidot lattices. Both effects can be explained in a classical Kubo approach by considering the trajectories of charge carriers in the semiconductor, when Andreev reflection at the semiconductor-superconductor interface is included. For perfect Andreev reflection, we expect a complete suppression of the commensurability features, even though motion at finite B is chaotic., Comment: 4 pages, 4 figures

The high-pressure behaviour of Bi2Fe4O9 was analysed by in situ powder and single-crystal x-ray diffraction and Raman spectroscopy. Pressures up to 34.3(8) GPa were generated using the diamond anvil cell technique. A reversible phase transition is observed at approximately 6.89(6) GPa and the high-pressure structure is stable up to 26.3(1) GPa. At higher pressures the onset of amorphization is observed. The crystal structures were refined from single-crystal data at ambient pressure and pressures of 4.49(2), 6.46(2), 7.26(2) and 9.4(1) GPa. The high-pressure structure is isotypic to the high-pressure structure of Bi2Ga4O9. The lower phase transition pressure of Bi2Fe4O9 with respect to that of Bi2Ga4O9 (16 GPa) confirms the previously proposed strong influence of cation substitution on the high-pressure stability and the misfit of Ga3+ and Fe3+ in tetrahedral coordination at high pressure. A fit of a second-order Birch–Murnaghan equation of state to the p–V data results in K0 = 74(3) GPa for the low-pressure phase and K0 = 79(2) GPa for the high-pressure phase. The mode Grüneisen parameters were obtained from Raman-spectroscopic measurements.