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ISTerre is part of Labex OSUG@2020. Use of the Geochem- istry–Mineralogy platform at ISTerre is acknowledged. The authors wish to aknowledge the ESRF for provision of beam time (MA4498). We are also thankful to Dr Pierre-Olivier Autran for useful insights on tomographic reconstructions and Dr Marta Majkut for discussions on grain orientation calcu- lations. The authors also thank Dr Irina Snigireva and Dr Nathaniel Findling for SEM characterization of the samples and Dr Catherine Dejoie for complementary high-resolution powder diffraction data from the ID22 beamline of the ESRF., The mechanism of hydration of calcium sulfate hemihydrate (CaSO4 0.5H2O) to form gypsum (CaSO4 2H2O) was studied by combining scanning 3D X-ray diffraction (s3DXRD) and phase contrast tomography (PCT) to determine in situ the spatial and crystallographic relationship between these two phases. From s3DXRD measurements, the crystallographic structure, orientation and position of the crystalline grains in the sample during the hydration reaction were obtained, while the PCT reconstructions allowed visualization of the 3D shapes of the crystals during the reaction. This multi-scale study unfolds structural and morphological evidence of the dissolution–precipitation process of the gypsum plaster system, providing insights into the reactivity of specific crystallographic facets of the hemihydrate. In this work, epitaxial growth of gypsum crystals on the hemihydrate grains was not observed.

Nature chemistry 15(5), 641 - 646 (2023). doi:10.1038/s41557-023-01148-7, The recent high-pressure synthesis of pentazolates and the subsequent stabilization of the aromatic $[N_5]^−$ anion at atmospheric pressure have had an immense impact on nitrogen chemistry. Other aromatic nitrogen species have also been actively sought, including the hexaazabenzene $N_6 $ring. Although a variety of configurations and geometries have been proposed based on ab initio calculations, one that stands out as a likely candidate is the aromatic hexazine anion $[N_6]^{4−}$. Here we present the synthesis of this species, realized in the high-pressure potassium nitrogen compound $K_9N_{56}$ formed at high pressures (46 and 61 GPa) and high temperature (estimated to be above 2,000 K) by direct reaction between nitrogen and $KN_3$ in a laser-heated diamond anvil cell. The complex structure of $K_9N_{56}$—composed of 520 atoms per unit cell—was solved based on synchrotron single-crystal X-ray diffraction and corroborated by density functional theory calculations. The observed hexazine anion $[N_6]^{4−}$ is planar and proposed to be aromatic., Published by Nature Publishing Group, London

The asbestos bodies (AB) form in the lungs as the result of an in vivo biomineralization process started by the alveolar macrophages in the attempt to isolate asbestos and become the actual interface between asbestos and the host organism. The AB are believed to be mainly composed of the Fe-proteins and mucopolyssaccharides. However, the presence of hydroxyapatite and Fe-oxy(hydro)oxides, other than ferrihydrite (the mineral core of ferritin), has also been proposed. We performed synchrotron X-ray diffraction (XRD) and absorption (XAS) measurements to unravel the Fe form in the AB and to check the crystallinity of the inner fiber. XRD results revealed the presence of goethite and that the inner fiber (crocidolite) maintained a high degree of crystallinity despite the prolonged stay in the lungs (>10y). XAS results, on the other hand, revealed the co-existence of ferrihydrite and goethite. The results are discussed in terms of the higher toxicity of goethite with respect to ferrihydrite.

Two novel yttrium nitrides, YN

The choice of studying nano and micro natural fibres can be exciting and lead to successful scientific stories, but not always results are immediate and it can take several years to get some.One of the main challenges is to obtain an accurate structure analysis of natural samples, as they do not form crystals large enough for single-crystal x-ray diffraction (SC-XRD), and their analysis is often hampered by reflection overlap and the coexistence of multiple fibres linked together.The advent of high-brightness, fourth generation synchrotron sources and improvements in X-ray focusing optics [1] has enabled new techniques for materials investigations with nanometre spatial resolution.Possibilities for multiscale characterization for environmental mineralogy using the same probe, together with the high penetration power and coherence, are some of the most advantageous factors of synchrotron X-ray sources and the case of asbestos materials can benefit by the bright and small beam available in synchrotron facilities, especially at ID11, the Materials Science Beamline at the ESRF.Challenges and results collected over the past 10 years studying natural fibres will be shown in this contribution. [1] Snigirev, A. A., Snigireva, I., Grigoriev, M., Yunkin, V., Di Michiel, M., Kuznetsov, S. & Vaughan, G. (2007). Proc. SPIE, 6795, 670506

Tin halide perovskites have the potential to overcome the toxicity issues of lead-based systems for photovoltaic devices. Elucidation of local structural features in these systems is of fundamental relevance to better understand the optoelectronic properties. This has been realized in ASnX3 (A= MA, FA, and X= I, Br) by total scattering and X-ray pair distribution function analysis, showing a trend of increasing local distortion as a function of organic cation, halide and temperature.

Nature 605(7909), 274 - 278 (2022). doi:10.1038/s41586-022-04550-2, Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions1,2. Hitherto, their synthesis and investigation above 200 gigapascals have been hindered both by the technical complexity of ultrahigh-pressure experiments and by the absence of relevant in situ methods of materials analysis. Here we report on a methodology developed to enable experiments at static compression in the terapascal regime with laser heating. We apply this method to realize pressures of about 600 and 900 gigapascals in a laser-heated double-stage diamond anvil cell3, producing a rhenium–nitrogen alloy and achieving the synthesis of rhenium nitride Re$_7$N$_3$—which, as our theoretical analysis shows, is only stable under extreme compression. Full chemical and structural characterization of the materials, realized using synchrotron single-crystal X-ray diffraction on microcrystals in situ, demonstrates the capabilities of the methodology to extend high-pressure crystallography to the terapascal regime., Published by Nature Publ. Group, London [u.a.]

We present the first nitridic analogs of micas, namely AE Si 3 P 4 N 10 (NH) 2 ( AE = Mg, Mg 0.94 Ca 0.06 , Ca, Sr), which were synthesized under high-pressure high-temperature conditions at 1400 °C and 8 GPa from the refractory nitrides P 3 N 5 and Si 3 N 4 , the respective alkaline earth amides, implementing NH 4 F as a mineralizer. The crystal structure was elucidated by single-crystal diffraction with microfocused synchrotron radiation, energy-dispersive X-ray spectroscopic (EDX) mapping with atomic resolution, powder X-ray diffraction, and solid-state NMR. The structures consist of typical tetrahedra-octahedra-tetrahedra ( T - O - T ) layers with P occupying T and Si occupying O layers, realizing the rare motif of sixfold coordinated silicon atoms in nitrides. The presence of H, as an imide group forming the SiN 4 (NH) 2 octahedra, is confirmed by SCXRD, MAS-NMR, and IR spectroscopy. Eu 2+ doped samples show tunable narrow-band emission from deep blue to cyan (451 - 492 nm).

We present the first nitridic analogs of micas, namely AESi

The high-resolution powder diffraction beamline at ESRF (ID22), built with a dual-undulator source on the 6 GeV storage ring, combines a wide continuous range of incident energy (6–80 keV) with high brightness, offering the possibility to carry out high-flux high-resolution powder diffraction measurements. In routine operation, a bank of nine scintillation detectors is scanned vertically to measure the diffracted intensity versus 2θ, each detector being preceded by an Si 111 analyser crystal. Although the current detector system has operated successfully for the past 20 years, recent developments in detector technology could be exploited to improve the overall performance. With this in mind, as a test, a two-dimensional Pilatus3 X CdTe 300 K-W pixel detector has been mounted on the arm of the diffractometer, replacing the nine scintillator detectors. At each nominal 2θ value, a two-dimensional image is recorded showing nine distinct regions corresponding to the diffraction signals passing via each of the analyser crystals. This arrangement offers new flexibility in terms of data handling and processing, with the possibility to optimize both peak shape and statistics, to remove parasitic effects, and to gain spatial resolution information. Combining the high efficiency of a hybrid photon-counting area detector with the high angular resolution given by analyser crystals is an effective approach to improving the overall performance of high-resolution powder diffraction.

We utilize the solvent acidolysis crystallization technique to grow mixed dimethylammonium/methylammonium lead tribromide (DMA/MAPbBr3 ) crystals reaching the highest dimethylammonium incorporation of 44% while maintaining the 3D cubic perovskite phase. These mixed perovskite crystals show suppression of the orthorhombic phase and a lower tetragonal to cubic phase transition temperature compared to MAPbBr3 . We observe distinct behavior in the temperature-dependent photoluminescence properties of MAPbBr3 and mixed DMA/MAPbBr3 crystals due to the different organic cation dynamics governing the phase transition(s). Furthermore, we fabricate lateral photodetectors which show that, at room temperature, the mixed crystals possess higher detectivity compared to MAPbBr3 crystals caused by structural compression and reduced surface trap density. Remarkably, the mixed crystal devices exhibit large enhancement in their detectivity below the phase transition temperature (at 200K), while the MAPbBr3 devices demonstrate insignificant changes. The higher detectivity makes our devices attractive for visible light communication and for space applications. Our results highlight the importance of the synthetic technique for the halide perovskites compositional engineering that governs their structural and optoelectronic properties. This article is protected by copyright. All rights reserved.

We report on the impact of magnetoelastic coupling on the magnetocaloric properties of ${\mathrm{LaFe}}_{11.4}{\mathrm{Si}}_{1.6}{\mathrm{H}}_{1.6}$ in terms of the vibrational (phonon) density of states (VDOS), which we determined with $^{57}\mathrm{Fe}$ nuclear resonant inelastic x-ray scattering (NRIXS) measurements and with density functional theory (DFT) based first-principles calculations in the ferromagnetic (FM) low-temperature and paramagnetic (PM) high-temperature phase. In experiments and calculations, we observe pronounced differences in the shape of the Fe-partial VDOS between nonhydrogenated and hydrogenated samples. This shows that hydrogen not only shifts the temperature of the first-order phase transition, but also affects the elastic response of the Fe subsystem significantly. In turn, the anomalous redshift of the Fe VDOS, observed by going to the low-volume PM phase, survives hydrogenation. As a consequence, the change in the Fe-specific vibrational entropy $\mathrm{\ensuremath{\Delta}}{S}_{\mathrm{lat}}$ across the phase transition has the same sign as the magnetic and electronic contribution. DFT calculations show that the same mechanism, which is a consequence of the itinerant electron metamagnetism associated with the Fe subsystem, is effective in both the hydrogenated and the hydrogen-free compounds. Although reduced by 50% as compared to the hydrogen-free system, the measured change $\mathrm{\ensuremath{\Delta}}{S}_{\mathrm{lat}}$ of $(3.2\ifmmode\pm\else\textpm\fi{}1.9)\phantom{\rule{0.16em}{0ex}}\frac{\mathrm{J}}{\mathrm{kg}\phantom{\rule{0.16em}{0ex}}\mathrm{K}}$ across the FM-to-PM transition contributes with $\ensuremath{\sim}35$% significantly and cooperatively to the total isothermal entropy change $\mathrm{\ensuremath{\Delta}}{S}_{\mathrm{iso}}$. Hydrogenation is observed to induce an overall blueshift of the Fe VDOS with respect to the H-free compound; this effect, together with the enhanced Debye temperature observed, is a fingerprint of the hardening of the Fe sublattice by hydrogen incorporation. In addition, the mean Debye velocity of sound of ${\mathrm{LaFe}}_{11.4}{\mathrm{Si}}_{1.6}{\mathrm{H}}_{1.6}$ was determined from the NRIXS and the DFT data.

The search for high Li-ion conducting ceramics has regained tremendous interest triggered by the renaissance of the all-solid-state battery. Within this context we herein reveal the impact of structural polymorphism of lithium copper pyroborate Li6CuB4O10 on its ionic conductivity. Using combined in situ synchrotron X-ray and neutron powder diffraction, a structural and synthetic relationship between α- and β-Li6CuB4O10 could be established and its impact on ionic conductivity evolution was followed using electrochemical impedance spectroscopy. We show that the high temperature form of Li6CuB4O10 exhibits a high Li-ion conductivity (2.7 mS cm–1 at 350 °C) and solve its crystal structure for the first time. Our results emphasize the significant impact of structural phase transitions on ionic conductivity and show possible high Li-ion mobility within borate based compounds.

The ferrierite crystal structure has often been subject to discussion because of the possible lowering of symmetry from the space group Immm. It mainly occurs in nature with a fibrous crystal habit, and because of the existence of line/planar defects in the framework, texture and preferred orientation effects it has been difficult to obtain an exact crystallographic model based only on the results from powder diffraction data. Therefore, nano-single-crystal diffraction and tomography data have been combined in order to improve the refinement with a meaningful model. High-quality single-crystal data, providing reliable structural information, and tomography images have been used as input for a Rietveld refinement which took into account a phenomenological description of stacking disorder and the analytical description of the preferred orientation, by means of spherical harmonics for strong texture effects. This is one of the first examples of application of synchrotron nano-diffraction for the structure solution of fibrous minerals of micrometre to nanometre size. The high quality of the crystals allowed collection of single-crystal X-ray diffraction data of up to 0.6 Å resolution, leading to an unambiguous solution and precise anisotropic refinement. Nano-single-crystal diffraction and phase contrast tomography data were collected at ID11 and the high-resolution powder diffraction patterns at ID22 of the European Synchrotron Radiation Facility. This detailed crystallographic characterization provides a basis for understanding the potential of ferrierite for toxicity and carcinogenicity.

A new end station for high energy (30–70 keV) X-ray diffraction experiments with nano-focus (150–500 nm) beam sizes has been installed at beamline ID11 at the ESRF. We review some of the early results from this instrument. High resolution crystal structure determination and refinement could be achieved with samples smaller than 3 μm in size. Near surfaces, the in-plane strain has been mapped as a function of depth in an oxide coating only 6 μm in thickness with 200 nm resolution. Via scanning diffraction tomography methods, then type-III intra-grain strain fields have been measured for fine-grained materials (

Nowadays, due to the adverse health effects associated with exposure to asbestos, its removal and thermal inertization has become one of the most promising ways for reducing waste risk management. Despite all the advances in structure analysis of fibers and characterization, some problems still remain that are very hard to solve. One challenge is the structure analysis of natural micro- and nano-crystalline samples, which do not form crystals large enough for single-crystal X-ray diffraction (SC-XRD), and their analysis is often hampered by reflection overlap and the coexistence of multiple fibres linked together. In this paper, we have used nano-focused synchrotron X-rays to refine the crystal structure of a micrometric tremolite fibres from Val d&rsquo, Ala, Turin (Italy) after various heat treatment. The structure of the original fibre and after heating to 800 &deg, C show minor differences, while the fibre that was heated at 1000 &deg, C is recrystallized into pyroxene phases and cristobalite.

The metal-organic frameworks (MOFs) M(BPZNO(2)) (M=Co, Cu, Zn; H(2)BPZNO(2)=3-nitro-4,4-bipyrazole) were prepared through solvothermal routes and were fully investigated in the solid state. They showed good thermal stability both under a N-2 atmosphere and in air, with decomposition temperatures peaking up to 663 K for Zn(BPZNO(2)). Their crystal structure is characterized by 3D networks with square (M=Co, Zn) or rhombic (M=Cu) channels decorated by polar NO2 groups. As revealed by N-2 adsorption at 77 K, they are micro-mesoporous materials with BET specific surface areas ranging from 400 to 900 m(2)g(-1). Remarkably, under the mild conditions of 298 K and 1.2 bar, Zn(BPZNO(2)) adsorbs 21.8 wt% CO2 (4.95 mmolg(-1)). It shows a Henry CO2/N-2 selectivity of 15 and an ideal adsorbed solution theory (IAST) selectivity of 12 at p=1 bar. As a CO2 adsorbent, this compound is the best-performing MOF to date among those bearing a nitro group as a unique chemical tag. High-resolution powder X-ray diffraction at 298 K and different CO2 loadings revealed, for the first time in a NO2-functionalized MOF, the insurgence of primary host-guest interactions involving the C(3)-NO2 moiety of the framework and the oxygen atoms of carbon dioxide, as confirmed by Grand Canonical Monte Carlo simulations. This interaction mode is markedly different from that observed in NH2-functionalized MOFs, for which the carbon atom of CO2 is involved.

We present the results of a study on the thermal stability and dehydration dynamics of the porous aluminophosphate AlPO4-5, from room temperature to 850 °C, carried out by in situ synchrotron X-ray powder diffraction experiments. No phase transitions were observed in the investigated T range. Due to the very low interactions among framework and water molecules, dehydration is already complete at 152 °C. It occurs in two main T ranges, one between 60 and 80 °C and the second one between 90 and 120 °C. During these two stages, the cell volume tends to increase to facilitate the water release. Overall, across the full explored T range, the cell volume increase is only 0.84%, indicating that AlPO4-5 is one of the most rigid zeolite frameworks studied to date. Specifically, after complete dehydration at 200 °C, AlPO4-5 undergoes a negative thermal expansion as a consequence of the decrease in both a and c cell parameters. The expansion coefficients for V, a and c cell parameters, in the 152–850 °C range, are αV = −7.12 (10−6/K), αa = −2.5 (10−6/K), αc = −2.2 (10−6/K), respectively.

Twenty-five glassy samples, including fragments of objects, molten glass and glass drops originating from a Proto-Byzantine glass workshop of the Catania Roman Amphitheatre, were analysed for major, minor and trace elements. Two main groups of natron-based silica–lime glass were identified, as well as one sample of obsidian (from Lipari Island). The majority of the samples (20) are High Iron, Manganese and Titanium (HIMT) glass. Specifically, most of them (18) can be classified as HIMT1, with only two HIMT2 glasses, according to the latest classification proposed in the literature. Three samples belong to the Levantine I type. In regard to the geochemical signatures of HIMT raw materials, the high abundance of HREE relative to LREE and of HFS elements (Zr, Nb, Ta, Ti, Hf, Th), suggests the use of impure sand, particularly enriched in heavy minerals and/or in mafic phases. Furthermore, the noticeably different contents of all the HFSE in the two main sample sub-groups – enriched HIMT and depleted Levantine I – allow us to propose these elements as discriminating factors between the two glass categories, which were present at the same time.

International audience; The origin of the 2-order of magnitude difference in the proton conductivity of the hydrated forms of hexagonal and cubic oxygen deficient BaScxTi1-xO3-delta (x = 0.2 and x = 0.7) was probed using a combination of neutron diffraction and density functional theory techniques to support published X-ray diffraction, conductivity, thermogravimetric and differential scanning calorimetry studies. Cation ordering is found in the 6H structure type (space group P6(3)/mmc) adopted by BaSc0.2Ti0.8O3-delta with scandium preferentially substituting in the vertex sharing octahedra (2a crystallographic site) and avoiding the facesharing octahedra (4f site). This is coupled with oxygen vacancy ordering in the central plane of the facesharing octahedra (O1 site). In BaSc0.7Ti0.3O3-delta a simple cubic perovskite (space group Pm3m) best represents the average structure from Rietveld analysis with no evidence of either cation ordering or oxygen vacancy ordering. Significant diffuse scattering is observed, indicative of local order. Hydration in both cases leads to complete filling of the available oxygen vacancies and permits definition of the proton sites. We suggest that the more localised nature of the proton sites in the 6H structure is responsible for the significantly lower proton conduction observed in the literature. Within the 6H structure type final model, proton diffusion requires a 3-step process via higher energy proton sites that are unoccupied at room temperature and is also likely to be anisotropic whereas the highly disordered cubic perovskite proton position allows 3-dimensional diffusion by well-described modes. Finally, we propose how this knowledge can be used to further materials design for ceramic electrolytes for proton conducting fuel cells

A thorough structural exploration has been made on the quasi-one-dimensional S = 1/2 compound Li 2 Cu 2 O(SO 4) 2 by neutron and synchrotron x-ray diffraction. It reveals the occurrence of a structural transition at 125 K, characterized by a lowering of symmetry from P 4 2 /m to P ¯ 1, which is possibly driven by an exchange striction mechanism. This transition involves a dimerization of some Cu in the edge-sharing tetrahedral Cu chains. A symmetry mode analysis indicates that one representation, 3 + 4 + , dominates the structural transition. Interestingly, no intermediate structure with P 112/m symmetry is observed experimentally. Lastly, temperature dependent magnetic susceptibility measurements and neutron diffraction reveal that the magnetic ground state of this compound is a spin-singlet with a spin gap, characterized by the absence of long-range magnetic order down to 1.7 K.

We have performed high-resolution powder x-ray diffraction measurements on a sample of $^{242}$PuCoGa$_{5}$, the heavy-fermion superconductor with the highest critical temperature $T_{c}$ = 18.7 K. The results show that the tetragonal symmetry of its crystallographic lattice is preserved down to 2 K. Marginal evidence is obtained for an anomalous behaviour below $T_{c}$ of the $a$ and $c$ lattice parameters. The observed thermal expansion is isotropic down to 150 K, and becomes anisotropic for lower temperatures. This gives a $c/a$ ratio that decreases with increasing temperature to become almost constant above $\sim$150 K. The volume thermal expansion coefficient $\alpha_{V}$ has a jump at $T_{c}$, a factor $\sim$20 larger than the change predicted by the Ehrenfest relation for a second order phase transition. The volume expansion deviates from the curve expected for the conventional anharmonic behaviour described by a simple Gr\"{u}neisen-Einstein model. The observed differences are about ten times larger than the statistical error bars but are too small to be taken as an indication for the proximity of the system to a valence instability that is avoided by the superconducting state., Comment: 6 pages, 4 figures

International audience; This paper reports a study, performed by in-situ synchrotron X-ray Powder Diffraction, of the high pressure behavior of the natural zeolite amicite [K4Na4(Al8Si8O32)10H(2)O], the GIS-type phase with ordered (Si, Al) and (Na, K) distribution. The experiments were carried out up to 8.13(5) GPa in methanol:ethanol:water = 16:3:1 (m.e.w.) and 8.68(5) GPa in silicone oil (s.o.). The crystal structure refinements of the patterns collected in m.e.w. were performed up to 4.71(5) GPa, while for the patterns collected in s.o. only the unit cell parameters were determined as a function of pressure. The observed framework deformation mechanismsimilar to that reported for the other studied phases with GIS topologyis essentially driven by the distortion of the double crankshaft chains and the consequent changed shape of the 8-ring channels. The pressure-induced over-hydration observed in the experiment performed in aqueous medium occurs without unit cell volume expansion, and is substantially reversible. A comparison is made with the high pressure behavior of the other GIS-type phases, and the strong influence on compressibility of the chemical composition of both framework and extraframework species is discussed

The structural origin of the remarkable performance of the metal–organic framework Fe2(BPEB)3 as a CO2 adsorbent (40.5% of the host weight at 298 K and 10 bar) was investigated by combining advanced experimental and computational tools. In situ and operando high-resolution and high-energy powder X-ray diffraction experiments were carried out at 273 and 298 K dosing CO2 in the pressure range of 0–9 bar and 0–21 bar, respectively. Juxtaposing a conventional approach for structural determination and refinement with total scattering analysis enabled us to unveil the adsorption sites occupied by the gaseous probe and the host–guest interactions at 298 K and all the assayed pressures. These studies were complemented by molecular dynamics simulations to support the location of the guest molecules inside the host channels and characterize the energetics of the host–guest and guest–guest interactions. Our molecular-level insight into the nature of the host–guest interactions in Fe2(BPEB)3, a rigid host without exposed metal sites or functional groups with particular affinity to CO2 on the ligand, provides key information on a debated topic, namely the chemical and structural properties a host should possess for efficient CO2 adsorption under rather mild conditions.

The honeycomb-lattice ruthenate ${\mathrm{Li}}_{2}{\mathrm{RuO}}_{3}$ is made heavily Li deficient by chemical oxidation by iodine. The delithiation induces a different phase ${\mathrm{Li}}_{2\ensuremath{-}x}{\mathrm{RuO}}_{3}$, the ``D phase,'' with superlattice. For the first time we disclose the magnetic and structural properties of the D phase in the dimer-solid state. The low-temperature magnetic susceptibility and the bond lengths indicate a bonding configuration consisting of both ${\mathrm{Ru}}^{4+}\text{\ensuremath{-}}{\mathrm{Ru}}^{4+}$ and ${\mathrm{Ru}}^{5+}\text{\ensuremath{-}}{\mathrm{Ru}}^{5+}$ dimers.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Microcrystalline vinpocetine, coground with cross-linked polyvinylpyrrolidone, affords hybrids containing nanosized drug nanocrystals, the size and size distributions of which depend on milling times and drug-to-polymer weight ratios. Using an innovative approach to microstructural characterization, we analyzed wide-angle X-ray total scattering data by the Debye function analysis and demonstrated the possibility to characterize pharmaceutical solid dispersions obtaining a reliable quantitative view of the physicochemical status of the drug dispersed in an amorphous carrier. The microstructural properties derived therefrom have been successfully employed in reconciling the enigmatic difference in behavior between in vitro and in vivo solubility tests performed on nanosized vinpocetine embedded in a polymeric matrix.

The five metal azolate/carboxylate (MAC) compounds [Cd(dmpzc)(DMF)(H2O)] (Cd-dmpzc), [Pd(H2dmpzc)2Cl2] (Pd-dmpzc), [Cu(Hdmpzc)2] (Cu-dmpzc), [Zn4O(dmpzc)3]·Solv (Zn-dmpzc·S), and [Co4O(dmpzc)3]·Solv (Co-dmpzc·S) were isolated by coupling 3,5-dimethyl-1H-pyrazol-4-carboxylic acid (H2dmpzc) to cadmium(II), palladium(II), copper(II), zinc(II), and cobalt(II) salts. While Cd-dmpzc and Pd-dmpzc had never been prepared in the past, for Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S we optimized alternative synthetic paths that, in the case of the copper(II) and cobalt(II) derivatives, are faster and grant higher yields than the previously reported ones. The crystal structure details were determined ab initio (Cd-dmpzc and Pd-dmpzc) or refined (Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S) by means of powder X-ray diffraction (PXRD). While Cd-dmpzc is a nonporous 3D MAC framework, Pd-dmpzc shows a 3D hybrid coordination/hydrogen-bonded network, in which Pd(H2dmpzc)2Cl2 monomers are present. The thermal behavior of the five MAC compounds was investigated by coupling thermal analysis to variable-temperature PXRD. Their catalytic activity was assessed in oxidative and C-C coupling reactions, with the copper(II) and cadmium(II) derivatives being the first nonporous MAC frameworks to be tested as catalysts. Cu-dmpzc is the most active catalyst in the partial oxidation of cyclohexane by tert-butyl hydroperoxide in acetonitrile (yields up to 12% after 9 h) and is remarkably active in the solvent-free microwave-assisted oxidation of 1-phenylethanol to acetophenone (yields up to 99% at 120 °C in only 0.5 h). On the other hand, activated Zn-dmpzc·S (Zn-dmpzc) is the most active catalyst in the Henry C-C coupling reaction of aromatic aldehydes with nitroethane, showing appreciable diastereoselectivity toward the syn-nitroalkanol isomer (syn:anti selectivity up to 79:21).

Despite the importance of martensitic transformations of Ni-Mn-Ga Heusler alloys for their magnetocaloric and shape-memory properties, the martensitic part of their phase diagrams is not well determined. Using an ab initio approach that includes the interplay of lattice and vibrational degrees of freedom we identify an intermartensitic transformation between a modulated and a nonmodulated phase as a function of excess Ni and Mn content. Based on an evaluation of the theoretical findings and experimental x-ray diffraction data for Mn-rich alloys, we are able to predict the phase diagram for Ni-rich alloys. In contrast to other mechanisms discussed for various material systems in the literature, we herewith show that the intermartensitic transformation can be understood solely using thermodynamic concepts.

International audience; Using a combination of high resolution X-ray powder diffraction and X-ray Raman scattering spectroscopy at the B K- and Ca L-2,L-3-edges, we analyzed the reaction products of Ca(BH4)(2) after annealing at 350 degrees C and 400 degrees C under vacuum conditions. We observed the formation of nanocrystalline/amorphous CaB6 mainly and found only small contributions from amorphous B for annealing times larger than 2 h. For short annealing times of 0.5 h at 400 degrees C we observed neither CaB12H12 nor CaB6. The results indicate a reaction pathway in which Ca(BH4)(2) decomposes to B and CaH2 and finally reacts to form CaB6. These findings confirm the potential of using Ca(BH4)(2) as a hydrogen storage medium and imply the desired cycling capabilities for achieving high-density hydrogen storage materials

The thermal transformation, stability field, and reaction kinetics of serpentine minerals (antigorite, chrysotile, and lizardite) have been studied to draw a comprehensive model for their dehydroxylation and recrystallization reactions. In situ X-ray powder diffraction (XRPD) and kinetic studies were combined with transmission electron microscopy (TEM) observations to describe the mechanisms of dehydroxylation and later high-temperature crystallization. During dehydroxylation, a metastable transition phase with a characteristic peak around 9 A was observed in antigorite and, to a minor extent, in lizardite. Rietveld refinements confirmed that the 9 A phase actually possesses a talc-like structure. The appearance of this phase is controlled by structure and kinetic factors. The kinetic parameters and reaction mechanism for lizardite and antigorite dehydroxylation in air at ambient pressure were calculated using the Avrami models and compared to those of chrysotile. For both lizardite and antigorite, the kinetics of dehydroxylation is controlled by diffusion. Apparent activation energy of the reaction in the temperature range 612–708 °C was 221 and 255 kJ/mol for lizardite and antigorite, respectively. The reaction sequences of chrysotile, lizardite, and antigorite leading to the formation of stable high-temperature products (i.e., forsterite and enstatite) are described taking into account previous topotactic and dissolution-recrystallization models.