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In the quest to find powerful modifiers of screen-printed electrodes for sensing applications, a set of rare earth-doped Ca10−xREx(PO4)6(OH)2 (RE = La, Nd, Sm, Eu, Dy, and Tm and x = 0.01, 0.02, 0.10, and 0.20) hydroxyapatite (HAp) samples were subjected to an in-depth electrochemical characterization using electrochemical impedance spectroscopy and cyclic and square wave voltammetry. Among all of these, the inorganic phosphates doped with lanthanum proved to be the most reliable, revealing robust analytical performances in terms of sensitivity, repeatability, reproducibility, and reusability, hence paving the way for their exploitation in sensing applications. Structural data on La-doped HAp samples were also provided by using different techniques, including optical microscopy, X-ray diffraction, Rietveld refinement from X-ray data, Fourier transform infrared, and Raman vibrational spectroscopies, to complement the electrochemical characterization.

Innovative computational and graphical tools have been implemented for advancing the crystal structure solution process from powder diffraction data using the EXPO software. These improve the capacity of EXPO to tackle challenging solution cases and make the structural study of microcrystalline materials more user friendly. The novel features concern the structure solution both in reciprocal space and in direct space. For reciprocal-space solution, the new capability to solve an unknown structure from a mixture composed of one unknown structure and one or more phases with known structures is particularly valuable. For direct-space structure solution, EXPO has been enhanced by parallelized simulated annealing with the aim of both reducing the execution time of the solution process and providing a successful result when several degrees of freedom must be varied. Many other new tools, functional for overcoming practical difficulties usually encountered during the solution process, have also been completed. In particular, a new tool for searching and importing structures from the Crystallography Open Database is effective for supporting the solution process in direct space. The advances in EXPO aim to provide software with improved reliability, expanded operation and greater speed.

The scientific interest toward the structural, luminescence, and dielectric properties of tricalcium phosphate (TCP) materials, in particular, the doped TCP-based compounds, is mainly due to their biocompatibility and bioactivity behavior and the increasing number of their applications. In the literature, structural investigations of a doped ?-TCP compound are usually carried out by powder diffraction data under the assumption that it has a centrosymmetric whitlockite structure. Recent studies have shown that this assumption is not always fulfilled. For this reason, it is necessary to use methods of nonlinear and dielectric spectroscopy to prove the true symmetry of whitlockite-like phases. This work provides a detailed and comprehensive study on the structural, dielectric, and nonlinear properties of the polycrystalline Tb- and Ho-doped tricalcium phosphates, chemically Ca9Tb(PO4)7 and Ca9Ho(PO4)7. Their crystal structure was explored using powder X-ray diffraction, adopting an ab initio approach for the structure solution followed by the Rietveld refinement. For Ca9Tb(PO4)7, the qualitative analysis of the experimental powder X-ray diffraction pattern revealed that the sample was not a single phase. Nevertheless, its crystal structure has been determined by Direct Methods. The presence of the dopant cation was omitted in the solution process by Direct Methods and considered in the successive Rietveld refinement step. The analysis of the occupancies has clarified the Tb3+ cation distribution in its preferential sites. The same pathway has been followed for the Ca9Ho(PO4)7 sample, which corresponded to a single-phase structure. The dielectric properties of the two doped compounds (Tb3+ and Ho3+) were also examined, and reversible ferroelectric-paraelectric phase transitions were found at 862 and 872 K, respectively.

The title compound, 3N-ethyl-2N’-(2-ethylphenylimino)thiazolidin-4-one (C13H16N2OS), was synthesized and structurally studied by IR and (1H, 13C) NMR spectroscopy. The crystal structure of the title compound was investigated using powder X-ray diffraction (PXRD) data via Direct Methods and refined by the Rietveld method. The compound crystallizes in the tetragonal system, space group I−4 with cell constants: a = 16.99742(15) A, b = 16.99742(15) A, c = 9.2663(2) A, V = 2677.15(7) A3, Z = 8. The molecular geometry was optimized using the density functional theory (DFT/B3LYP) method with the 6-311G(d,p) basis set and compared to the experimental data. The experimental and theoretical structures are found to be consistent. The molecular packing of the title compound exhibits C H⋅⋅⋅O and O H⋅⋅⋅N hydrogen bonds forming supramolecular network. The details of the intermolecular interactions were studied through the Hirshfeld surface map and two-dimensional fingerprint plot. Detailed vibrational assignments and NMR chemical shifts were explored by DFT computation, showing good agreement with the experimental results. All the vibrational modes were assigned using the potential energy distribution (PED). UV–Visible spectrum in chloroform solvent was analyzed and electronic transitions involved in the title compound were predicted using the TD-DFT method. The direct and indirect band gaps were estimated using Tauc Plots via UV–Vis spectroscopy. Furthermore, the values of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy were calculated by the DFT method and their distribution was confirmed by the determination of DOS spectra. The global reactivity descriptors and the Fukui functions were evaluated. Mulliken population analysis and natural bond orbital (NBO) theory were used to compute atomic charges and the outcomes are consistent with the MEP map distribution.

Despite the increasing incidence of hepatocellular carcinoma (HCC) worldwide, current pharmacological treatments are still unsatisfactory. We have previously shown that lysophosphatidic acid receptor 6 (LPAR6) supports HCC growth and that 9-xanthenylacetic acid (XAA) acts as an LPAR6 antagonist inhibiting HCC growth without toxicity. Here, we synthesized four novel XAA derivatives, (±)-2-(9H-xanthen-9-yl)propanoic acid (compound 4 - MC9), (±)-2-(9H-xanthen-9-yl)butanoic acid (compound 5 - MC6), (±)-2-(9H-xanthen-9-yl)hexanoic acid (compound 7 - MC11), and (±)-2-(9H-xanthen-9-yl)octanoic acid (compound 8 - MC12, sodium salt) by introducing alkyl groups of increasing length at the acetic α-carbon atom. Two of these compounds were characterized by X-ray powder diffraction and quantum mechanical calculations, while molecular docking simulations suggested their enantioselectivity for LPAR6. Biological data showed anti-HCC activity for all XAA derivatives, with the maximum effect observed for MC11. Our findings support the view that increasing the length of the alkyl group improves the inhibitory action of XAA and that enantioselectivity can be exploited for designing novel and more effective XAA-based LPAR6 antagonists.

Pure and Co

Anionic complexes having vapochromic behavior are investigated: [K(H2O)][M(ppy)(CN)2], [K(H2O)][M(bzq)(CN)2], and [Li(H2O)n][Pt(bzq)(CN)2], where ppy = 2-phenylpyridinate, bzq = 7,8-benzoquinolate, and M = Pt(II) or Pd(II). These hydrated potassium/lithium salts exhibit a change in color upon being heated to 380 K, and they transform back into the original color upon absorption of water molecules from the environment. The challenging characterization of their structure in the vapochromic transition has been carried out by combining several experimental techniques, despite the availability of partially ordered and/or impure crystalline material. Room-temperature single-crystal and powder X-ray diffraction investigation revealed that [K(H2O)][Pt(ppy)(CN)2] crystallizes in the Pbca space group and is isostructural to [K(H2O)][Pd(ppy)(CN)2]. Variable-temperature powder X-ray diffraction allowed the color transition to be related to changes in the diffraction pattern and the decrease in sample crystallinity. Water loss, monitored by thermogravimetric analysis, occurs in two stages, well separated for potassium Pt compounds and strongly overlapped for potassium Pd compounds. The local structure of potassium compounds was monitored by in situ pair distribution function (PDF) measurements, which highlighted changes in the intermolecular distances due to a rearrangement of the crystal packing upon vapochromic transition. A reaction coordinate describing the structural changes was extracted for each compound by multivariate analysis applied to PDF data. It contributed to the study of the kinetics of the structural changes related to the vapochromic transition, revealing its dependence on the transition metal ion. Instead, the ligand influences the critical temperature, higher for ppy than for bzq, and the inclination of the molecular planes with respect to the unit cell planes, higher for bzq than for ppy. The first stage of water loss triggers a unit cell contraction, determined by the increase in the b axis length and the decrease in the a (for ppy) or c (for bzq) axis lengths. Consequent interplane distance variations and in-plane roto-translations weaken the π-stacking of the room-temperature structure and modify the distances and angles of Pt(II)/Pd(II) chains. The curve describing the intermolecular Pt(II)/Pd(II) distances as a function of temperature, validated by X-ray absorption spectroscopy, was found to reproduce the coordinate reaction determined by the model-free analysis., This research has been supported by the short-term mobility program of the National Research Council (CNR) of Italy and by the Spanish Ministerio de Economía y Competitividad (Ministerio de Ciencia Innovación y Universidades)/FEDER (Project PGC2018-094749-B-I00).

Pure and Co3+-doped BaAl2O4 [Ba(Al1–xCox)2O4, x = 0, 0.0077, 0.0379] powder samples were prepared by a facile hydrothermal route. Elemental analyses by static secondary ion mass spectrometry (SIMS), X-ray absorption spectroscopy (XAS) measurements at the Co K- edge, and X-ray diffraction studies were fully correlated, thus addressing a complete description of the structural complexity of Co3+- doped BaAl2O4 powder. Powder X-ray diffraction (PXRD) patterns indicated that prepared samples were nanocrystalline with a hexagonal P63 symmetry. The X-ray absorption near-edge structure (XANES) measurements revealed the presence of cobalt in a +3 oxidation state, while the rarely documented, tetrahedral symmetry around Co3+ was extracted from the extended X-ray absorption fine structure (EXAFS) oscillation patterns. Rietveld structure refinements showed that Co3+ preferentially substitutes Al3+ at tetrahedral Al3 sites of the BaAl2O4 host lattice, whereas the (Al3)O4 tetrahedra remain rather regular with Co3+–O distances ranging from 1.73(9) to 1.74(9) Å. The underlying magneto- structural features were unraveled through axial and rhombic zero-field splitting (ZFS) terms. The increased substitution of Al3+ by Co3+ at Al3 sites leads to an increase of the axial ZFS terms in Co3+-doped BaAl2O4 powder from 10.8 to 26.3 K, whereas the rhombic ZFS parameters across the series change in the range from 2.7 to 10.4 K, showing a considerable increase of anisotropy together with the values of the anisotropic g- tensor components flowing from 1.7 to 2.5. We defined the line between the Co3+ doping limit and influenced magneto- structural characteristics, thus enabling the design of strategy to control the ZFS terms’ contributions to magnetic anisotropy within Co3+-doped BaAl2O4 powder.

The important role played by powder diffraction in the last twenty-five years both in its earlier fields of application (e [...]

A molecule-based ferroelectric triethylmethylammonium tetrachloroferrate(III) ([N(C

Europium-doped hydroxyapatite Ca10(PO4)6(OH)2 (3% mol) powders were synthesized by an optimized chemical precipitation method at 25 &deg, C, followed by drying at 120 &deg, C and calcination at 450 &deg, C and 900 &deg, C. The obtained nanosized crystallite samples were investigated by means of a combination of inductively coupled plasma (ICP) spectroscopy, powder X-ray diffraction (PXRD), Fourier Transform Infrared (FTIR), Raman and photoluminescence (PL) spectroscopies. The Rietveld refinement in the hexagonal P63/m space group showed europium ordered at the Ca2 site at high temperature (900 &deg, C), and at the Ca1 site for lower temperatures (120 &deg, C and 450 &deg, C). FTIR and Raman spectra showed slight band shifts and minor modifications of the (PO4) bands with increasing annealing temperature. PL spectra and decay curves revealed significant luminescence emission for the phase obtained at 900 &deg, C and highlighted the migration of Eu from the Ca1 to Ca2 site as a result of increasing calcinating temperature.

The solution of crystal structures from X-ray powder diffraction data has undergone intense development in the last 25 years. Overlapping, background estimate, and preferred orientation are the main difficulties in the process of determining a crystal structure from the analysis of the mono-dimensional powder diffraction pattern. EXPO is a well-known computer program that is designed to solve organic, inorganic, and metal&ndash, organic structures by powder diffraction data, employing the two most widely used kinds of solution methods: Direct Methods, working in the reciprocal space, and Simulated Annealing, working in the real space. EXPO also allows the suitable combination of these two approaches to validate the structural solution. In this paper, we give examples of structure characterization by EXPO with the aim of suggesting a solution strategy for the application of reciprocal-space methods or real-space methods, or both.

We report the first transition metal catalyst- and ligand-free conjugate addition of lithium tetraorganozincates (R4ZnLi2) to nitroolefins. Displaying enhanced nucleophilicity combined with unique chemoselectivity and functional group tolerance, homoleptic aliphatic and aromatic R(4)ZnLi(2)provide access to valuable nitroalkanes in up to 98 % yield under mild conditions (0 degrees C) and short reaction time (30 min). This is particularly remarkable when employing beta-nitroacrylates and beta-nitroenones, where despite the presence of other electrophilic groups, selective 1,4 addition to the C=C is preferred. Structural and spectroscopic studies confirmed the formation of tetraorganozincate species in solution, the nature of which has been a long debated issue, and allowed to unveil the key role played by donor additives on the aggregation and structure of these reagents. Thus, while chelatingN,N,N',N'-tetramethylethylenediamine (TMEDA) and (R,R)-N,N,N',N'-tetramethyl-1,2-diaminocyclohexane (TMCDA) favour the formation of contacted-ion pair zincates, macrocyclic Lewis donor 12-crown-4 triggers an immediate disproportionation process of Et(4)ZnLi(2)into equimolar amounts of solvent-separated Et3ZnLi and EtLi.

A molecule-based ferroelectric triethylmethylammonium tetrachloroferrate(III) ([N(C2H5)(3)CH3][FeCl4]) powder was designed as a multifunctional material exhibiting excellent multiple bistability. Prepared by the slow evaporation method at room temperature, the compound crystallizes in the non-centrosymmetric assembly of hexagonal symmetry (P6(3)mc space group) which undergoes a reversible temperature-triggered phase transition pinpointed at 363 K to the centrosymmetric packing within the P6(3)/mmc space group. Aside from the inseparable role of the symmetry-breaking process smoothly unveiled from the X-ray powder diffraction data, a striking change in the dielectric permittivity observed during the paraelectric-to-ferroelectric phase transition directly discloses the bistable dielectric behavior-an exceptionally high increase in the dielectric permittivity of about 360% at 100 kHz across the heating and cooling cycles is direct proof showing the highly desirable stimuli-responsive electric ordering in this improper ferroelectric architecture. Due to the magnetically modulated physical properties resulting in the coupling of magnetic and electric orderings, the flexible assembly of [N(C2H5)(3)CH3][FeCl4] could be used to boost the design and development of novel magnetoelectric devices.

Silver lanthanum diphosphates doped with terbium, AgLa1-xTbxP2O7 (x=0%, 1%, 5%, 10%, 15% and 20%), were prepared by solid state reaction at T=500°. The obtained compounds were investigated by means of a multi-methodological approach, involving the Scanning Electron Microscopy (SEM) equipped with energy dispersive X-Ray spectroscopy (EDS) for morphological investigation and semi-quantitative chemical analysis, respectively; powder X-ray diffraction (PXRD) for structural characterization and Rietveld refinement; Fourier Transform InfraRed (FTIR) and Raman spectroscopies for qualitative study. Finally, emission spectra were collected in order to detect the fluorescence properties of the compounds. The unit cell parameters and the space group of all the family members were determined by PXRD data. The compounds crystallize in the orthorhombic Pnma space group, with the AgLaP2O7 cell constants equal to: a = 8.6706(1) A, b = 5.3218(1) A, c = 12.8839(1) A and cell volume V = 594.51(1) A3. A decreasing trend for unit cell parameters was observed at increase of dopant concentration. For the pure phase, the investigation was completed with the structure solution via Direct Methods and Rietveld refinement. The crystal structure consists of compact layers of LaO9 polyhedra, down the c axis, bridged by P2O7 diphosphate groups and by zig-zag chains of AgO9 polyhedra down b. The FTIR and Raman analysis supports the chemical structure, highlighting the deformation (δPO3) and stretching (νPO3) vibration of PO3 groups, and the characteristic bands of P2O74- groups attributed to the symmetric and asymmetric stretching (νs and νas) of P-O-P bridge, respectively. The luminescence properties of Tb3+ activating ion in AgLa1-xTbxP2O7 (x=1%, 5%, 10%, 15% and 20%) were also examined. No concentration quenching of the main 5D4-→7F5 emission, responsible for the well known green emission of Tb3+ ion, was observed in the studied concentration range, whereas a concentration quenching of the emission from 5D3 level, due to 5D3-→5D4 cross relaxation process, was revealed.

Chemical preparation, crystal structure and vibrational study are reported on a new diphenylhydrazine dihydrogenophosphate (C 6 H 9 N 2 ) 2 H 2 P 2 O 7 (DPHDP) single crystal. This organic cationic diphosphate compound was synthesized by the method of ion exchange resin . (C 6 H 9 N 2 ) 2 H 2 P 2 O 7 crystallizes in the monoclinic system. The structural resolution shows the existence of H 2 P 2 O 7 2− ion chains linked together by hydrogen bonds. The organic cations C 6 H 9 N 2 + and the phosphate chains are linked together by hydrogen bonds. The vibrational study by IR spectroscopy of the title compound reveals the presence of three bands and confirms the existence of non-equivalent positions of water molecules in the structure.

The Shift_and_Fix procedure is a new method which has been developed for improving the quality of a structure model obtained by the ab initio solution process from powder diffraction data. The main features of the new approach, which is fully automatic, are as follows: (a) the structure model usually attained at the end of the phasing process by direct methods is shifted partly and randomly; (b) a combination of Fourier map calculation and least-squares cycles has been designed for relocating the shifted atoms onto positions which can finally be moved onto the true ones by the standard model optimization approaches; (c) the Fourier map is calculated using coefficients which depend on the chemical content of the compound under study. When the figure of merit for selecting the best set of phases derived by direct methods does not work well, the ALLTRIALS strategy can be applied: it aims to investigate, automatically and sequentially, all the stored direct methods phasing sets and pick up the correct solution. The Shift_and_Fix method has been applied for improving the structure model calculated by each one of the phasing sets processed by ALLTRIALS. It has been implemented in the computer program EXPO and proved to be effective in providing a better ALLTRIALS outcome and increasing the probability of succeeding in the ab initio powder solution.

To obtain novel muscarinic acetylcholine receptor (mAChR) antagonists, the enantiomers of the hybrid compounds 3-5, in which the quinuclidin-3-yloxy fragment of solifenacin and the 6,6-diphenyl-1,4dioxane-2-yl moiety of 2 linked by an ester or ether spacer were embedded in the same chemical entity, were prepared and evaluated for their affinity at the five mAChR subtypes (M-1-M-5). Stereochemistry and the nature of the linker between the quinuclidine moiety and the 1,4-dioxane nucleus play an important role on the affinities of the compounds. The presence of an ether bridge confers higher affinities for all mAChR subtypes to the ligand. Interestingly, the ether enantiomer (R,S)-5 shows the highest affinity at all mAChR subtypes with K-p(i) values similar to that of solifenacin at M-3 and higher at the other subtypes. Unlike solifenacin, it shows a preference for M-1 mAChR subtype with respect to the other subtypes. This compound, lacking a permanent positive charge on the nitrogen atom, can be a useful tool for the pharmacological study of mAChRs in the central nervous system. (C) 2017 Elsevier Masson SAS. All rights reserved.

The phase identification of a polycrystalline mixture by X-ray powder diffraction data is often requested for studying materials interesting to different scientific and technological fields: chemistry, pharmaceutics, mineralogy, archeometry, forensic science, etc. The availability of user friendly computer programs, able to carry out qualitative phase analysis in efficient and possibly automatic way, is extremely useful to the scientific community involved in powder diffraction. QUALX2.0, the evolution of QUALX, is a freely distributed software for qualitative phase analysis. Based on the traditional search–match method, it is able to manage both a commercial database (PDF-2 maintained by ICDD), and a freely available database (POW_COD generated by the structure information contained in the Crystallography Open Database). QUALX2.0 is continuously improved in terms of computing and graphic tools. Correspondingly, the database POW_COD is suitably modified to make efficient the operations of search. The search–match approach can be facilitated by the use of restraints, when available, involving the chemical composition, the kind of compound(s) (e.g., organic, inorganic, etc.), the symmetry (space group, crystal system), the unit-cell parameters and/or volume, the crystal properties (measured and/or calculated crystal density, crystal color). An outline of the main features of QUALX2.0 and an example of application is described.

Two examples of anionic complexes having vapochromic behavior are investigated: [K(H2O)][Pt(ppy)(CN)2] “Pt(ppy)” and [K(H2O)][Pt(bzq)(CN)2] “Pt(bzq)”, where ppy = 2-phenylpyridinate and bzq = 7,8-benzoquinolate. These monohydrate-potassium salts exhibit a change in color from purple to yellow [Pt(ppy)] and from red to yellow [Pt(bzq)] upon heating to 110 °C, and they transform back into the original color upon absorption of water molecules from the environment. Available only in the form of polycrystalline samples, no structural information on such compounds is accessible, due to highly overlapping peaks in powder diffraction profiles. We use in situ Pair Distribution Function measurements on powder samples to investigate the dynamics of the structural changes induced by temperature variations. By means of a multivariate approach, we were able to extract dynamic structural information from collected profiles without using prior knowledge on the static crystal structure of the compounds. The critical temperature and the characteristics of the vapochromic transition have been identified, as well as the main structural changes causing it.

This paper describes new features implemented in the EXPO2014 software and aimed at assisting crystallographers in the use of quantum-chemistry calculations in combination with experimental powder diffraction data. The implemented tools are useful in particular in two important steps of the process of crystal structure determination from powder diffraction data: (1) preparing accurate structural model suitable for crystal structure determination by real-space methods; (2) validating structure determination. The combination of experimental/quantum-chemical methods in EXPO2014 is now managed easily thanks to the following capabilities: (a) converting crystallographic data in input files and reading molecular geometry from output files of a wide variety of computational chemistry packages (GAMESS-US, NWChem, Gaussian, CRYSTAL, ABINIT, QUANTUM ESPRESSO); (b) optimizing the geometry of a molecule using Open Babel's force fields; (c) a graphical interface to run semi-empirical quantum calculation by MOPAC (Molecular Orbital PACkage); (d) producing input file for dispersion-corrected density functional theory.

Three hydrated double layered vanadium oxides, namely Na0.35V2O5·0.8(H2O), K0.36(H3O)0.15V2O5 and (NH4)0.37V2O5·0.15(H2O), were obtained by using mild hydrothermal conditions. Their delta type structural frameworks were solved by high-resolution synchrotron X-ray powder diffraction and the interlayer spacings were interpreted from difference Fourier maps. The inter-slab distances are modulated by the water content and the special arrangements of the alkali and ammonium cations. The XPS measurements denote mixed valence systems with high contents of V4+ ions up to 40%. The monitoring of the V4+ EPR signal over time suggests a reduction of the electronic delocalization on account of the partial oxidation to V5+. The electrochemical performance of the active phases is strongly conditioned by the vacuum-drying process of the electrodes, showing better capacity retention when vacuum is not applied. In situ X-ray diffraction shows a structural mechanism of contraction/expansion of the bilayers upon lithium insertion/extraction where the alkali ions behave as structural stabilizers. Galvanostatic cycling at very low current density implies migration of the alkali "pillars" triggering the collapse of the structure.

A new synthetic route to N-alkyl-2-acylazetidines was developed through a highly stereoselective addition of organolithiums to N-alkyl-2‐oxazolinylazetidines followed by acidic hydrolysis of the resulting oxazolidine intermediates. This study revealed an unusual reactivity of the C=N bond of the oxazoline group when reacted with an organolithiums in a non-polar solvent such as toluene. The observed reactivity has been explained considering the role of the nitrogen lone pair of the azetidine ring as well as of the oxazolinyl group in promoting a complexation of the organolithium, thus ending up with the addition to the C=N double bond. The high level of stereoselectivity in this addition is supported by DFT calculations and NMR investigations, and a model is proposed for the formation of the oxazolidine intermediates, that have been isolated and fully characterized. Upon acidic conditions, the oxazolidine moieties were readily converted into 2-acylazetidines. This synthetic approach has been applied for the preparation of highly enantioenriched 2-acylazetidines starting from chiral not racemic N‐alkyl-2‐oxazolinylazetidines.

C a 2.90 M e 0.10 2 + ( P O 4 ) 2 (with Me = Mn, Ni, Cu) &beta, tricalcium phosphate (TCP) powders were synthesized by solid-state reaction at T = 1200 &deg, C and investigated by means of a combination of scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, and luminescence spectroscopy. SEM morphological analysis showed the run products to consist of sub spherical microcrystalline aggregates, while EDS semi-quantitative analysis confirmed the nominal Ca/Me composition. The unit cell and the space group were determined by X-ray powder diffraction data showing that all the compounds crystallize in the rhombohedral R3c whitlockite-type structure, with the following unit cell constants: a = b = 10.41014(19) &Aring, c = 37.2984(13) &Aring, and cell volume V = 3500.53(15) &Aring, 3 (Mn), a = b = 10.39447(10) &Aring, c = 37.2901(8) &Aring, V = 3489.22(9) &Aring, 3 (Ni), a = b = 10.40764(8) &Aring, c = 37.3158(6) &Aring, V = 3500.48(7) &Aring, 3 (Cu). The investigation was completed with the structural refinement by the Rietveld method. The FTIR spectra are similar to those of the end-member Ca &beta, tricalcium phosphate (TCP), in agreement with the structure determination, and show minor band shifts of the (PO4) modes with the increasing size of the replacing Me2+ cation. Luminescence spectra and decay curves revealed significant luminescence properties for Mn and Cu phases.

Silver terbium diphosphate AgTbP2O7 was prepared by solid state reaction at T=500° and characterized by combining SEM-EDS morphological investigation and semi-quantitative chemical analysis via Scanning Electron Microscopy (SEM) equipped with energy dispersive X-Ray spectroscopy (EDS), structure solution via Rietveld refinement of powder X-ray diffraction (PXRD) data, and Fourier transform infrared (FTIR) spectroscopy. The synthesized compound is monoclinic, P21/n space group, with cell parameters: a=11.9108(3) Å, b=6.90265(16) Å, c=6.62030(15) Å, β=90.3702(5)° and V=544.28(2) Å3. The crystal structure consists of a network of zig-zag chains of TbO8 polyhedra extending along the b axis, bridged by P2O7 diphosphate groups and by chains of AgO7 polyhedra running along the c crystallographic direction. MIR (medium infrared) spectrum shows bands typical of P–O modes of diphosphate compounds. Observed band multiplicity is in agreement with the symmetry reduction with respect to orthorhombic rare earth diphosphates with similar stoichiometries reported in the literature.

Inorganic materials that enable a link between the storage and release of molecular oxygen offer a fertile ground in continuous quest for the applications that can potentially reduce energy consumption and thus minimize adverse effects on the environment. Herein, we address reversible intake/release of an oxygen within the BaAl2O4 material as evidenced by unexpected magnetic ordering. Magnetic measurements unveil that an oxygen is stored in the form of condensed matter, creating a kind of low dimensional, chain-like assembly within the tunnels of BaAl2O4 structure. We demonstrate that oxygen is adsorbed simply by staying in air, at ambient conditions, and released relatively quickly by staying in the He or other gas atmosphere of several millibars pressure even at 300 K.

The Rietveld method is the most reliable and powerful tool for refining crystal structure when powder diffraction data are available. It requires that the structure model to be adjusted is as close as possible to the true structure. The Rietveld method usually represents the final step of the powder solution process, in particular when a new structure is going to be determined and published. EXPO is a software able to execute all the steps of the solution process in a mostly automatic way, by starting from the chemical formula and the experimental diffraction pattern, passing through computational methods for locating the structure model and optimizing it, and ending to the Rietveld refinement. In this contribution, we present the most recent solution strategies in EXPO, both in reciprocal and direct space, aiming at obtaining models suitable to be refined by the Rietveld method. Examples of Rietveld refinements are described, whose results are related to different solution procedures and types of compounds (organic and inorganic).

This book offers an exhaustive analysis of the relationships between solid-state chemistry and the processes of drug design and development. The aim of clarifying how fundamental the knowledge is o...

The hybrid big bang–big crunch algorithm is a combination of a global optimization algorithm inspired by one of the theories of the evolution of the universe, named the big bang and big crunch theory, and the simulated annealing method. The procedure was implemented in the latest version of the programEXPOand applied to crystal-structure solution from powder diffraction data. Several aspects of the hybrid big bang–big crunch algorithm can be further optimized with the aim of obtaining good quality solutions in a shorter computation time. In the present study, the hybrid big bang–big crunch procedure has been combined with the greedy randomized adaptive search procedure (GRASP) and some steps of the algorithm have been improved. The new approach, implemented in theEXPOpackage, has been successfully tested on numerous known crystal structures.

The Shift_and_Fix procedure is a new method which has been developed for improving the quality of a structure model obtained by the ab initio solution process from powder diffraction data. The main features of the new approach, which is fully automatic, are as follows: (a) the structure model usually attained at the end of the phasing process by direct methods is shifted partly and randomly; (b) a combination of Fourier map calculation and least-squares cycles has been designed for relocating the shifted atoms onto positions which can finally be moved onto the true ones by the standard model optimization approaches; (c) the Fourier map is calculated using coefficients which depend on the chemical content of the compound under study. When the figure of merit for selecting the best set of phases derived by direct methods does not work well, the ALLTRIALS strategy can be applied: it aims to investigate, automatically and sequentially, all the stored direct methods phasing sets and pick up the correct solution. The Shift_and_Fix method has been applied for improving the structure model calculated by each one of the phasing sets processed by ALLTRIALS. It has been implemented in the computer program EXPO and proved to be effective in providing a better ALLTRIALS outcome and increasing the probability of succeeding in the ab initio powder solution.