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The effect of specimen displacement in X‐ray powder diffraction experiments with laboratory diffractometers has been revisited and new expressions have been derived for several commonly used experimental configurations, including Bragg–Brentano parafocusing geometry and flat‐plate transmission geometry. The results presented in this work allow the analysis of data from samples with relatively large displacements. This may open the possibility to study samples with dimensions that are difficult to accommodate with the sample‐handling capabilities of standard laboratory diffractometers. [ABSTRACT FROM AUTHOR]

The objective of crystal structure prediction (CSP) is to predict computationally the thermodynamically stable crystal structure of a compound from its stoichiometry or its molecular diagram. Crystal similarity indices measure the degree of similarity between two crystal structures and are essential in CSP because they are used to identify duplicates. Powder‐based indices, which are based on comparing X‐ray diffraction patterns, allow the use of experimental X‐ray powder diffraction data to inform the CSP search. Powder‐assisted CSP presents two unique difficulties: (i) the experimental and computational structures are not entirely comparable because the former is subject to thermal expansion from lattice vibrations, and (ii) experimental patterns present features (noise, background contribution, varying peak shapes etc.) that are not easily predictable computationally. This work presents a powder‐based similarity index (GPWDF) based on a modification of the index introduced by de Gelder, Wehrens & Hageman [J. Comput. Chem. (2001), 22, 273–289] using cross‐correlation functions that can be calculated analytically. Based on GPWDF, a variable‐cell similarity index (VC‐GPWDF) is also proposed that assigns a high similarity score to structures that differ only by a lattice deformation and which takes advantage of the analytical derivatives of GPWDF with respect to the lattice parameters. VC‐GPWDF can be used to identify similarity between two computational structures generated using different methods, between a computational and an experimental structure, and between two experimental structures measured under different conditions (e.g. different temperature and pressure). VC‐GPWDF can also be used to compare crystal structures with experimental patterns in combination with an automatic pre‐processing step. The proposed similarity indices are simple, efficient and fully automatic. They do not require indexing of the experimental pattern or a guess of the space group, they account for deformations caused by varying experimental conditions, they give meaningful results even when the experimental pattern is of very poor quality, and their computational cost does not increase with the flexibility of the molecular motif. [ABSTRACT FROM AUTHOR]

FullProfAPP is a software tool for data processing, refinement and visualization of large collections of powder diffraction patterns. Featuring an intuitive graphical user interface, it seamlessly facilitates a variety of tasks. These include conducting full‐profile phase searches, sequential and high‐throughput Rietveld refinements, and managing background (and peak) detection. FullProfAPP also provides convenient interaction with crystallographic databases and supports the visualization and export of high‐quality pixel and vector graphics depicting the refinement results, among other functionalities. FullProfAPP wraps around the refinement program FullProf [Rodríguez‐Carvajal (1993), Physica B, 192, 55–69] and offers the flexibility of user‐defined workflows by accessing and editing FullProf's input files and triggering its execution as necessary. FullProfAPP is distributed as open‐source software and is presently available for Windows and Linux operating systems. [ABSTRACT FROM AUTHOR]

In recent years, there is a significant interest from the crystallographic and materials science communities to have access to raw diffraction data. The effort in archiving raw data for access by the user community is spearheaded by the International Union of Crystallography (IUCr) Committee on Data. In materials science, where powder diffraction is extensively used, the challenge in archiving raw data is different to that from single crystal data, owing to the very nature of the contributions involved. Powder diffraction (X‐ray or neutron) data consist of contributions from the material under study as well as instrument specific parameters. Having raw powder diffraction data can be essential in cases of analysing materials with poor crystallinity, disorder, micro structure (size/strain) etc. Here, the initiative and progress made by the International Centre for Diffraction Data (ICDDR) in archiving powder X‐ray diffraction raw data in the Powder Diffraction FileTM (PDFR) database is outlined. The upcoming 2025 release of the PDF‐5+ database will have more than 20800 raw powder diffraction patterns that are available for reference. [ABSTRACT FROM AUTHOR]

The atomic pair distribution function (PDF) is a real‐space representation of the structure of a material. Experimental PDFs are obtained using a Fourier transform from total scattering data which may or may not have Bragg diffraction peaks. The determination of Bragg peak resolution in scattering data from the fundamental physical parameters of the diffractometer used is well established, but after the Fourier transform from reciprocal to direct space, these contributions are harder to identify. Starting from an existing definition of the resolution function of large‐area detectors for X‐ray diffraction, this approach is expanded into direct space. The effect of instrumental parameters on PDF peak resolution is developed mathematically, then studied with modelling and comparison with experimental PDFs of LaB6 from measurements made in different‐sized capillaries. [ABSTRACT FROM AUTHOR]

X-ray diffraction (XRD) characterization of Si powder was carried out using synchrotron and laboratory sources. Microstructural (size-strain) analyses of XRD patterns were carried out using the Rietveld refinement method. Experimentally observed super-Lorentzian shapes of the XRD peaks of Si powder were examined using multimodal profile fitting and bimodal model was found to be adequate. The two components obtained using a bimodal approach are referred as narrow and broad profiles based on their estimated relative peak widths. Peak shapes of crystallite size-dependent parts of narrow and broad profiles were found to be almost Gaussian and Lorentzian in nature, respectively. The simultaneous presence of such peak shapes corresponding to a bimodal microstructure is uncommon in literature. Therefore, in order to explore the role of different natures of XRD peak shapes (size dependent) of the bimodal profiles of Si, detailed microstructural analysis was carried out using the complementary method of whole powder pattern modeling (WPPM) and found to be related to the variance of crystallites' size distribution. Additionally, the effect of instrument resolution (laboratory and synchrotron sources) on the microstructural parameters was also studied. Scanning and transmission electron microscopy were used to characterize the morphology of Si powder and correlate with the microstructural findings of XRD methods. [ABSTRACT FROM AUTHOR]

Leucites are tetrahedrally coordinated silicate framework structures with some of the silicon framework cations that are partially replaced by divalent or trivalent cations. These structures have general formulae A 2 B Si5O12 and AC Si2O6, where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. There are also leucite analogs with analogous tetrahedrally coordinated germanate framework structures. These have general formulae A 2 B Ge5O12 and AC Ge2O6. In this paper, the Rietveld refinements of three synthetic Ge-leucite analogs with stoichiometries of A AlGe2O6 (A = K, Rb, Cs) are discussed. KAlGe2O6 is I 41 /a tetragonal and is isostructural with KAlSi2O6. RbAlGe2O6 and CsAlGe2O6 are $I\bar{4}3d$ cubic and are isostructural with KBSi2O6. [ABSTRACT FROM AUTHOR]

A monoclinic C form of rilpivirine hydrochloride, (N6H19C22)Cl, has been obtained and characterized using solid-state 15N, 13C, and 35Cl NMR spectroscopy and multitemperature synchrotron X-ray powder diffraction. The title compound crystallizes in the monoclinic system (space group C 2/ c , #15) at both room (295.0(2) K) and low (100.0(2) K) temperatures. At room temperature, the following parameters are a = 19.43051(3), b = 13.09431(14), c = 17.10254(18) Å, β = 109.3937(7), V = 4104.48(9) Å3, and Z = 8. The folded molecular conformation of the cation is similar with that of free base rilpivirine with the exception of cyanovinyl group disposition. The anion links cations to infinite chains parallel to the crystallographic c axis using N–H⋯Cl bonds where both amino groups and the protonated pyrimidine ring take part in the H-bonding. The powder patterns have been submitted to the ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

The crystal structure of brimonidine hydrogen tartrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Brimonidine hydrogen tartrate crystallizes in space group P21 (#4) with a = 7.56032(2), b = 7.35278(2), c = 30.10149(9) Å, β = 90.1992(2)°, V = 1673.312(10) Å3, and Z = 4 at 295 K. The crystal structure consists of alternating layers of cations and anions parallel to the ab -plane. Each of the hydrogen tartrate anions is linked to itself by very strong charge-assisted O–H⋯O hydrogen bonds into chains along the a -axis. Each hydroxyl group of each tartrate acts as a donor in an O–H⋯O or O–H⋯N hydrogen bond. One of these is intramolecular, but the other three are intermolecular. These hydrogen bonds link the hydrogen tartrate anions into layers parallel to the ab -plane and also link the anion–cation layers. The protonated N atoms act as donors in N–H⋯O or N–H⋯N hydrogen bonds to the carboxyl groups of the tartrates and to a ring nitrogen atom. These link the cations and anions, as well as providing cation–cation links. The amino N atoms of the cations form N–H⋯O hydrogen bonds to hydroxyl groups of the anions. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®) [ABSTRACT FROM AUTHOR]

Spectroscopic data, particularly diffraction data, are essential for materials characterization due to their comprehensive crystallographic information. The current crystallographic phase identification, however, is very time consuming. To address this challenge, we have developed a real-time crystallographic phase identifier based on a convolutional self-attention neural network (CPICANN). Trained on 692 190 simulated powder X-ray diffraction (XRD) patterns from 23 073 distinct inorganic crystallographic information files, CPICANN demonstrates superior phase-identification power. Single-phase identification on simulated XRD patterns yields 98.5 and 87.5% accuracies with and without elemental information, respectively, outperforming JADE software (68.2 and 38.7%, respectively). Bi-phase identification on simulated XRD patterns achieves 84.2 and 51.5% accuracies, respectively. In experimental settings, CPICANN achieves an 80% identification accuracy, surpassing JADE software (61%). Integration of CPICANN into XRD refinement software will significantly advance the cutting-edge technology in XRD materials characterization.

Analytical calculations of absorption corrections for X‐ray powder diffraction experiments on non‐ideal samples with surface roughness, porosity or absorption contrasts from multiple phases require complex mathematical models to represent their material distribution. In a computational approach to this problem, a practicable ray‐tracing algorithm is formulated which is capable of simulating angle‐dependent absorption corrections in reflection geometry for any given rasterized sample model. Single or multiphase systems with arbitrary surface roughness, porosity and spatial distribution of the phases in any combination can be modeled on a voxel grid by assigning respective values to each voxel. The absorption corrections are calculated by tracing the attenuation of X‐rays along their individual paths via a modified shear‐warp algorithm. The algorithm is presented in detail and the results of simulated absorption corrections on samples with various surface modulations are discussed in the context of published experimental results. [ABSTRACT FROM AUTHOR]

The crystal structure of nintedanib esylate hemihydrate was refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Nintedanib esylate hemihydrate crystallizes in space group P-1 (#2) with a = 11.5137(1), b = 16.3208(4), c = 19.1780(5) Å, α = 69.0259(12), β = 84.4955(8), γ = 89.8319(6)°, V = 3347.57(3) Å3, and Z = 4 at 295 K. Hydrogen bonds are prominent in the crystal structure. The water molecule forms two medium-strength O–H⋯O hydrogen bonds to one of the esylate anions. The protonated nitrogen atom in each cation forms a N–H⋯O hydrogen bond to an esylate anion. The ring N–H groups form strong intramolecular N–H⋯O hydrogen bonds to carbonyl groups. The ring N–H groups form intramolecular N–H⋯O hydrogen bonds to esylate anions. Many C–H⋅⋅⋅O hydrogen bonds (and one C–H⋯N hydrogen bond), with aromatic C–H, methylene groups and methyl groups as donors, are present. The hydrogen bonding patterns of the two cations differ considerably. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®) [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound {systematic name: (4S,4aS,5aR,12aR)-4,7-bis(dimethylamino)-9-[(2,2-dimethylpropylamino)methyl]-1,10,11,12a-tetrahydroxy-3,12-dioxo-4a,5,5a,6-tetrahydro-4H-tetracene-2-carboxamide dihydrate, C29H40N4O7·2H2O} has been solved and refined using synchrotron X-ray powder diffraction data: it crystallizes in space group R3 with a = 24.34430 (7), c = 14.55212 (4) Å, V = 7468.81 (2) Å3 and Z = 9. Most of the hydrogen bonds are intramolecular, but two classical N—H...O intermolecular hydrogen bonds (along with probable weak C—H...O and C—H...N hydrogen bonds) link the molecules into a three-dimensional framework. The framework contains voids, which contain disordered water molecules. Keto–enol tautomerism is apparently important in this molecule, and the exact molecular structure is ambiguous.

iQual is a new computer program developed for qualitative phase analysis using powder diffraction data. It is based on a new database named Crystal_db, derived from the latest Crystallography Open Database. Crystal_db has been created with organized functional modules and optimized index structures, greatly enhancing the database's search efficiency. The iQual program offers users a wide range of querying capabilities and convenient visualization features. In addition to providing an efficient interactive interface, the program combines with the optimized database to enable efficient searching for and finding of the data entries that best match the experimental data for qualitative analysis of X‐ray diffraction patterns. The highlight of this search–match method lies in an effective two‐step approach that makes full use of the database structure. A preliminary screening is adopted, based on the five strongest diffraction peaks of each candidate phase, prior to scoring the candidate phases. Matrix operations in both screening and scoring processes enhance the program's efficiency. [ABSTRACT FROM AUTHOR]

The NaZr2P3O12 family of materials have shown low and tailorable thermal expansion properties. In this study, SrZr4P6O24 (SrO·4ZrO2·3P2O5), CaZr4P6O24 (CaO·4ZrO2·3P2O5), MgZr4P6O24 (MgO·4ZrO2·3P2O5), NaTi2P3O12 [½(Na2O·4TiO2·3P2O5)], NaZr2P3O12 [½(Na2O·4ZrO2·3P2O5)], and related solid solutions were synthesized using the organic–inorganic steric entrapment method. The samples were characterized by in‐situ high‐temperature X‐ray diffraction from 25 to 1500°C at the Advanced Photon Source and National Synchrotron Light Source II. The average linear thermal expansion of SrZr4P6O24 and CaZr4P6O24 was between −1 × 10−6 per °C and 6 × 10−6 per °C from 25 to 1500°C. The crystal structures of the high‐temperature polymorphs of CaZr4P6O24 and SrZr4P6O24 with R3c symmetry were solved by Fourier difference mapping and Rietveld refinement. This polymorph is present above ∼1250°C. This work measured thermal expansion coefficients to 1500°C for all samples and investigated the differences in thermal expansion mechanisms between polymorphs and between compositions. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound {systematic name: (4S,4aS,5aR,12aR)-4,7-bis(dimethylamino)-9-[(2,2-dimethylpropylamino)meth-yl]-1,10,11,12a-tetrahydroxy-3,12-dioxo-4a,5,5a,6-tetrahydro-4#-tetracene-2-carboxamide dihydrate, C29H40N4O7⋅2H2O} has been solved and refined using synchrotron X-ray powder diffraction data: it crystallizes in space group R3 with α = 24.34430 (7), c = 14.55212 (4) Å, V = 7468.81 (2) ų and Z = 9. Most of the hydrogen bonds are intramolecular, but two classical N--H…O intermolecular hydrogen bonds (along with probable weak C--H…O and C--H…N hydrogen bonds) link the molecules into a three-dimensional framework. The framework contains voids, which contain disordered water molecules. Keto-enol tauto-merism is apparently important in this molecule, and the exact molecular structure is ambiguous. [ABSTRACT FROM AUTHOR]

Reaction of FeCl2·4H2O with KSCN and 3-cyanopyridine (pyridine-3-carbonitrile) in ethanol accidentally leads to the formation of single crystals of Fe(NCS)(Cl)(3-cyanopyridine)4 or [FeCl(NCS)(C6H4N2)4]. The asymmetric unit of this compound consists of one FeII cation, one chloride and one thiocyanate anion that are located on a fourfold rotation axis as well as of one 3-cyanopyridine coligand in a general position. The FeII cations are sixfold coordinated by one chloride anion and one terminally N-bonding thiocyanate anion in trans-positions and four 3-cyanopyridine coligands that coordinate via the pyridine N atom to the FeII cations. The complexes are arranged in columns with the chloride anions, with the thiocyanate anions always oriented in the same direction, which shows the non-centrosymmetry of this structure. No pronounced intermolecular interactions are observed between the complexes. Initially, FeCl2 and KSCN were reacted in a 1:2 ratio, which lead to a sample that contains the title compound as the major phase together with a small amount of an unknown crystalline phase, as proven by powder X-ray diffraction (PXRD). If FeCl2 and KSCN is reacted in a 1:1 ratio, the title compound is obtained as a nearly pure phase. IR investigations reveal that the CN stretching vibration for the thiocyanate anion is observed at 2074 cm−1, and that of the cyano group at 2238 cm−1, which also proves that the anionic ligands are only terminally bonded and that the cyano group is not involved in the metal coordination. Measurements with thermogravimetry and differential thermoanalysis reveal that the title compound decomposes at 169°C when heated at a rate of 4°C min−1 and that the 3-cyanopyridine ligands are emitted in two separate poorly resolved steps. After the first step, an intermediate compound with the composition Fe(NCS)(Cl)(3-cyanopyridine)2 of unknown structure is formed, for which the CN stretching vibration of the thiocyanate anion is observed at 2025 cm−1, whereas the CN stretching vibration of the cyano group remain constant. This strongly indicates that the FeII cations are linked by μ-1,3-bridging thiocyanate anions into chains or layers.

Rietveld refinements are widely used for many purposes in the physical sciences. Conducting a Rietveld refinement typically requires expert input because correct results may require that parameters be added to the fit in the proper order. This order will depend on the nature of the data and the initial parameter values. A mechanism for computing the next parameter to add to the refinement is shown. The fitting function is evaluated with the current parameter value set and each parameter incremented and decremented by a small offset. This provides the partial derivatives with respect to each parameter, along with information to discriminate meaningful values from numerical computational errors. The implementation of this mechanism in the open‐source GSAS‐II program is discussed. This new method is discussed as an important step towards the development of automated Rietveld refinement technology. [ABSTRACT FROM AUTHOR]

The crystal structure of a new 1:1 cocrystal of carbamazepine and S‐naproxen (C15H12N2O·C14H14O3) was solved from powder X‐ray diffraction (PXRD). The PXRD pattern was measured at the high‐resolution beamline CRISTAL at synchrotron SOLEIL (France). The structure was solved using Monte Carlo simulated annealing, then refined with Rietveld refinement. The positions of the H atoms were obtained from density functional theory (DFT) ground‐state calculations. The symmetry is orthorhombic with the space group P212121 (No. 19) and the following lattice parameters: a = 33.5486 (9), b = 26.4223 (6), c = 5.3651 (10) Å and V = 4755.83 (19) Å3. [ABSTRACT FROM AUTHOR]

The structure of opal has long fascinated scientists. It occurs in a number of structural states, ranging from amorphous to exhibiting features of stacking disorder. Opal‐CT, where C and T signify cristobalite‐ and tridymite‐like interstratification, represents an important link in the length scales between amorphous and crystalline states. However, details about local atomic (dis)order and arrangements extending to long‐range stacking faults in opal polymorphs remain incompletely understood. Here, a multilevel modeling approach is reported that considers stacking states in correlation with the abundance of C and T segments as a high‐level structural parameter (i.e. not each atom). Optimization accounting for inter‐tetrahedral bond lengths and angles and the regularity of the silicate tetrahedra is included as lower levels of structural parameters. Together, a set of parameters with both coarse‐grained and atomistic features for different levels of structural details is refined. Structural disorder at the ∼10–100 Å distance scale is evaluated using experimental pair distribution function and diffraction datasets, comparing peak intensities, widths and asymmetry. This work presents a complete multilevel structural description of natural opal‐CT and explains many of the unusual features observed in X‐ray powder diffraction patterns. This modeling approach can be adopted generally for analyzing layered materials and their assembly into 3D structures. [ABSTRACT FROM AUTHOR]

Reaction of FeCl2·4H2O with KSCN and 3-cyano­pyridine (pyridine-3-carbo­nitrile) in ethanol accidentally leads to the formation of single crystals of Fe(NCS)(Cl)(3-cyano­pyridine)4 or [FeCl(NCS)(C6H4N2)4]. The asymmetric unit of this compound consists of one FeII cation, one chloride and one thio­cyanate anion that are located on a fourfold rotation axis as well as of one 3-cyano­pyridine coligand in a general position. The FeII cations are sixfold coordinated by one chloride anion and one terminally N-bonding thio­cyanate anion in trans-positions and four 3-cyano­pyridine coligands that coordinate via the pyridine N atom to the FeII cations. The complexes are arranged in columns with the chloride anions, with the thio­cyanate anions always oriented in the same direction, which shows the non-centrosymmetry of this structure. No pronounced inter­molecular inter­actions are observed between the complexes. Initially, FeCl2 and KSCN were reacted in a 1:2 ratio, which lead to a sample that contains the title compound as the major phase together with a small amount of an unknown crystalline phase, as proven by powder X-ray diffraction (PXRD). If FeCl2 and KSCN is reacted in a 1:1 ratio, the title compound is obtained as a nearly pure phase. IR investigations reveal that the CN stretching vibration for the thio­cyanate anion is observed at 2074 cm−1, and that of the cyano group at 2238 cm−1, which also proves that the anionic ligands are only terminally bonded and that the cyano group is not involved in the metal coordination. Measurements with thermogravimetry and differential thermoanalysis reveal that the title compound decomposes at 169°C when heated at a rate of 4°C min−1 and that the 3-cyano­pyridine ligands are emitted in two separate poorly resolved steps. After the first step, an inter­mediate compound with the composition Fe(NCS)(Cl)(3-cyano­pyridine)2 of unknown structure is formed, for which the CN stretching vibration of the thio­cyanate anion is observed at 2025 cm−1, whereas the CN stretching vibration of the cyano group remain constant. This strongly indicates that the FeII cations are linked by μ-1,3-bridg­ing thio­cyanate anions into chains or layers. [ABSTRACT FROM AUTHOR]

Perylene diimides (PDI) are workhorses in the field of organic electronics, owing to their appealing n‐semiconducting properties. Optimization of their performances is widely pursued by bay‐atom substitution and diverse imide functionalization. Bulk solids and thin‐films of these species crystallize in a variety of stacking configurations, depending on the geometry of the stable conformation of the polyaromatic core. We here demonstrate that 1,7‐dibromo‐substituted perylene diimides, PDI(H2Br2), possessing a heavily twisted conformation in the gas phase, in solution and in the solids, can be easily flattened in the solid state into centrosymmetric molecules if the polyaromatic cores form π–π stabilized chains. This is achieved by using axial residues with low stereochemical hindrance, as guaranteed by a single CH2/NH spacer directly linked to the imide function. Structural powder diffraction and DFT calculations on four newly designed species of the PDI(H2Br2) class coherently show that, thanks to the flexibility of the N−X−Ar link (X=CH2/NH), flat cores are indeed obtained by overcoming the interconversion barrier between twisted atropoisomers, of only 26.5 kJ mol−1. This strategy may then be useful to induce "anomalously flat" polyaromatic cores of different kinds (substituted acenes/rylenes) in the solid state, towards suitable crystal packing and orbital interactions for improved electronic performances. [ABSTRACT FROM AUTHOR]

The general-purpose powder diffractometer beamline (BL2-1) at the Stanford Synchrotron Radiation Lightsource (SSRL) is described. The evolution of design and performance of BL2-1 are presented, in addition to current operating specifications, applications and measurement capabilities. Recent developments involve a robotic sample changer enabling high-throughput X-ray diffraction measurements, applicable to mail-in and remote operations. In situ and operando capabilities to measure samples with different form factors (e.g. capillary, flat plate or thin film, and transmission) and under variable experimental conditions are discussed. Several example datasets and accompanying Rietveld refinements are presented. [ABSTRACT FROM AUTHOR]

The room-temperature and low-temperature structure(s) of Ba2NaNb5O15 (BNN) have been debated since the structure was proposed in the 1960s. This work revisits the structures and phase transitions of BNN, combining highresolution X-ray and neutron powder diffraction with density functional theory calculations. Temperature-dependent high-resolution X-ray powder diffraction patterns are collected from 4 to 918 K, and sequential batch Rietveld refinement using a symmetry mode approach to describe the structure is used to extract the main structural changes as a function of temperature. The data show that the average structure of BNN is best described by the Ama2 space group, and no other structural phase transitions were observed below the ferroelastic transition. The symmetry mode analysis, combining results from diffraction and density functional theory, shows significant octahedral tilting and corrugations of both the A1 and A2 sites along the c direction. A strong correlation between the spontaneous strain and the octahedral tilting was observed, and a potential connection with emerging microstructure at low temperatures is proposed, all enabled by the symmetry mode approach used in this work. [ABSTRACT FROM AUTHOR]

The dissolution rate of the anti-HIV drug saquinavir base (SQV), a poorly water-soluble and extremely low absolute bioavailability drug, was improved through a eutectic mixture formation approach. A screening based on a liquid-assisted grinding technique was performed using a 1:1 molar ratio of the drug and the coformers sodium saccharinate, theobromine, nicotinic acid, nicotinamide, vanillin, vanillic acid, and piperine (PIP), followed by differential scanning calorimetry (DSC). Given that SQV-PIP was the only resulting eutectic system from the screening, both the binary phase and the Tammann diagrams were adapted to this system using DSC data of mixtures prepared from 0.1 to 1.0 molar ratios in order to determine the exact eutectic composition. The SQV-PIP system formed a eutectic at a composition of 0.6 and 0.40, respectively. Then, a solid-state characterization through DSC, powder X-ray diffraction (PXRD), including small-angle X-ray scattering (SAXS) measurements to explore the small-angle region in detail, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and a powder dissolution test were performed. The conventional PXRD analyses suggested that the eutectic mixture did not exhibit structural changes; however, the small-angle region explored through the SAXS instrument revealed a change in the crystal structure of one of their components. FT-IR spectra showed no molecular interaction in the solid state. Finally, the dissolution profile of SQV in the eutectic mixture was different from the dissolution of pure SQV. After 45 min, approximately 55% of the drug in the eutectic mixture was dissolved, while, for pure SQV, 42% dissolved within this time. Hence, this study concludes that the dissolution rate of SQV can be effectively improved through the approach of using PIP as a coformer. [ABSTRACT FROM AUTHOR]

The room-temperature and low-temperature structure(s) of Ba2NaNb5O15 (BNN) have been debated since the structure was proposed in the 1960s. This work revisits the structures and phase transitions of BNN, combining highresolution X-ray and neutron powder diffraction with density functional theory calculations. Temperature-dependent high-resolution X-ray powder diffraction patterns are collected from 4 to 918 K, and sequential batch Rietveld refinement using a symmetry mode approach to describe the structure is used to extract the main structural changes as a function of temperature. The data show that the average structure of BNN is best described by the Ama2 space group, and no other structural phase transitions were observed below the ferroelastic transition. The symmetry mode analysis, combining results from diffraction and density functional theory, shows significant octahedral tilting and corrugations of both the A1 and A2 sites along the c direction. A strong correlation between the spontaneous strain and the octahedral tilting was observed, and a potential connection with emerging microstructure at low temperatures is proposed, all enabled by the symmetry mode approach used in this work. [ABSTRACT FROM AUTHOR]

The crystal structure of 5-(3-methoxyphenyl)indoline-2,3-dione (C15H11NO3) was solved and refined using laboratory powder diffraction data and optimized using density functional techniques. The title compound crystallizes in space group Pbca with a = 11.1772(3) Å, b = 7.92536(13) Å, c = 27.0121(7) Å, and V = 2392.82(10) Å3. The asymmetric unit contains one molecule. Isatin molecules are joined into almost flat chains along the a direction by N–H⋯O bonds. The chains are linked into layers by π-stacking interactions. Finally, the third dimension of the crystal is formed by weaker C–H⋯π and C–H⋯O contacts. [ABSTRACT FROM AUTHOR]

Synchrotron powder diffraction data is presented for a series of relatively phase-pure smectite clay mineral standards obtained from the Clay Minerals Society. Rietveld refinement using a model for turbostratic disorder was performed to estimate the lattice parameters and mineral impurities in the smectite standards. Bragg reflection lists and raw data have been provided for inclusion in the Powder Diffraction File. [ABSTRACT FROM AUTHOR]

Operando powder X-ray diffraction (PXRD) is a widely employed method for the investigation of structural evolution and phase transitions in electrodes for rechargeable batteries. Due to the advantages of high brilliance and high X-ray energies, the experiments are often carried out at synchrotron facilities. It is known that the X-ray exposure can cause beam damage in the battery cell, resulting in hindrance of the electrochemical reaction. This study investigates the extent of X-ray beam damage during operando PXRD synchrotron experiments on battery materials with varying X-ray energies, amount of X-ray exposure and battery cell chemistries. Battery cells were exposed to 15, 25 or 35 keV X-rays (with varying dose) during charge or discharge in a battery test cell specially designed for operando experiments. The observed beam damage was probed by µPXRD mapping of the electrodes recovered from the operando battery cell after charge/discharge. The investigation reveals that the beam damage depends strongly on both the X-ray energy and the amount of exposure, and that it also depends strongly on the cell chemistry, i.e. the chemical composition of the electrode.

The discovery of new 3D perovskites and their 2D and 1D analogues continues to attract the interest of the scientific community and therefore the understanding of their structural, optical, and physicochemical properties is of fundamental importance. Here, we report the one‐pot synthesis and the full characterization of 1D and 2D lead halide polycrystalline solids containing the rather rigid 1,4‐xylylenediammonium (pXDA) organic cation as spacer. We isolated 2D Dion‐Jacobson (DJ) perovskites, namely (pXDA)PbX4 (X=Cl, Br) and the mixed halide (pXDA)Pb(Br1–xIx)4 species (all based on 2D monolayers of corner‐sharing lead halide octahedra), and, for iodine, the (pXDA)Pb2I6. 2H2O phase, which contains 1D PbI3-∞ ${{\left[{{\rm { PbI}}}_{{\rm { 3}}}^{{\rm { -}}}\right]}_{{\rm { \infty }}}}$ ribbons. The latter species can be reversibly dehydrated by gentle heating, forming the isomorphous (pXDA)Pb2I6. crystal phase. These species, some of which have recently been studied in the frame of broad light emitters and for photovoltaic applications, have been characterized by variable‐temperature X‐ray diffraction methods, shedding light onto their anisotropic thermal responses, of utmost importance for day‐night cycling in functional devices. Spin‐coated thin films were also prepared and studied by means of synchrotron radiation grazing incidence X‐ray diffraction, SEM imaging and fluorescence spectroscopy experiments. [ABSTRACT FROM AUTHOR]

The high‐intensity time‐of‐flight (TOF) neutron diffractometer POWTEX for powder and texture analysis is currently being built prior to operation in the eastern guide hall of the research reactor FRM II at Garching close to Munich, Germany. Because of the world‐wide 3He crisis in 2009, the authors promptly initiated the development of 3He‐free detector alternatives that are tailor‐made for the requirements of large‐area diffractometers. Herein is reported the 2017 enterprise to operate one mounting unit of the final POWTEX detector on the neutron powder diffractometer POWGEN at the Spallation Neutron Source located at Oak Ridge National Laboratory, USA. As a result, presented here are the first angular‐ and wavelength‐dependent data from the POWTEX detector, unfortunately damaged by a 50g shock but still operating, as well as the efforts made both to characterize the transport damage and to successfully recalibrate the voxel positions in order to yield nonetheless reliable measurements. Also described is the current data reduction process using the PowderReduceP2D algorithm implemented in Mantid [Arnold et al. (2014). Nucl. Instrum. Methods Phys. Res. A, 764, 156–166]. The final part of the data treatment chain, namely a novel multi‐dimensional refinement using a modified version of the GSAS‐II software suite [Toby & Von Dreele (2013). J. Appl. Cryst.46, 544–549], is compared with a standard data treatment of the same event data conventionally reduced as TOF diffraction patterns and refined with the unmodified version of GSAS‐II. This involves both determining the instrumental resolution parameters using POWGEN's powdered diamond standard sample and the refinement of a friendly‐user sample, BaZn(NCN)2. Although each structural parameter on its own looks similar upon comparing the conventional (1D) and multi‐dimensional (2D) treatments, also in terms of precision, a closer view shows small but possibly significant differences. For example, the somewhat suspicious proximity of the a and b lattice parameters of BaZn(NCN)2 crystallizing in Pbca as resulting from the 1D refinement (0.008 Å) is five times less pronounced in the 2D refinement (0.038 Å). Similar features are found when comparing bond lengths and bond angles, e.g. the two N—C—N units are less differently bent in the 1D results (173 and 175°) than in the 2D results (167 and 173°). The results are of importance not only for POWTEX but also for other neutron TOF diffractometers with large‐area detectors, like POWGEN at the SNS or the future DREAM beamline at the European Spallation Source. [ABSTRACT FROM AUTHOR]

This article is the second part of a series dealing with the description and visualization of mathematical functions used to describe a powder diffraction pattern for teaching and education purposes. The first part dealt with the instrumental and sample contributions to the profile of a Bragg peak [Dinnebier & Scardi (2021). J. Appl. Cryst.54, 1811–1831]. The second part, here, deals with the mathematics and physics of the intensity in X‐ray powder diffraction. Scholarly scripts are again provided using the Wolfram language in Mathematica. [ABSTRACT FROM AUTHOR]

The field of hybrid organic–inorganic perovskite materials continues to attract the interest of the scientific community due to their fascinating properties and the plethora of promising applications in photovoltaic and optoelectronic devices. To enhance the efficiency and stability of perovskite-based devices, it is essential to discover novel compounds but also to investigate their various physicochemical, structural, and thermal properties. In this work, we report the synthesis and structural characterization of two novel hybrid lead bromide perovskites, combining the imidazolium cation (IMI) with methylammonium (MA) or formamidinium (FA) cations. The isolated polycrystalline powders were studied with X-ray powder diffraction (XPRD) and were formulated as (IMI)(MA)Pb2Br6, a 3D structure consisting of dimers of face-sharing octahedra linked in corner-sharing mode, and (IMI)(FA)PbBr4, a 2D (110) oriented layer structure with zig-zag corner-sharing octahedra. The thermal stability of (IMI)(MA)Pb2Br6 and (IMI)(FA)PbBr4 was investigated with thermogravimetric (TG) and differential scanning calorimetry (DSC) experiments which showed that both compounds are chemically stable (at least) up to 250 °C. Variable-temperature X-ray diffractometric (VT-XRD) studies of (IMI)(FA)PbBr4 highlighted a structural modification occurring above 100 °C, that is a phase transformation from triclinic to orthorhombic, via an elusive monoclinic phase. [ABSTRACT FROM AUTHOR]

Hydroxyapatite, a mineral of the apatite group, has an important and useful property. It has the propensity for various kinds of substitutions, which allows modification of its properties and expansion of the possibilities of applying the synthetic material. The properties of a synthesized substance depend on the way it is produced, as the synthesis conditions influence the structural and morphological characteristics of the particles being formed. This work shows that, in the case of mechanochemical synthesis with the introduction of iron cations as a dopant, the structure of hydroxyapatite, in which the dopant occupies the position of the calcium cation, is formed. This type of substitution is accompanied by a decrease in the lattice parameters of the hydroxyapatite. It is shown that iron cations predominantly possess a 3+ charge, which is independent of the charge of the initial reagent containing the iron cation. It is also found that in the process of mechanochemical synthesis under certain conditions, the simultaneous partial replacement of calcium cations with iron cations and phosphate groups with carbonate group can be implemented. The powders obtained by mechanochemical synthesis are characterized by powder diffraction, infrared spectroscopy, X-ray absorption near edge structure spectroscopy (XANES), and Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

The triclinic structures of poly[(μ4-4,4′-biphenyldicarboxylato)di-μ-hydroxido-dicobalt], [Co2(C14H8O4)(OH)2]n, and poly[(μ4-4,4′-biphenyldicarboxylato)di-μ-hydroxido-dinickel], [Ni2(C14H8O4)(OH)2]n, were established using laboratory X-ray powder diffraction data. These structures, as well as that of poly[(μ4-4,4′-biphenyldicarboxylato)di-μ-hydroxido-dimanganese], [Mn2(C14H8O4)(OH)2]n, were optimized using density functional techniques. The structure of diammonium 4,4′-biphenyldicarboxylate, 2NH4+·C14H8O42−, was also solved using laboratory powder data. The Mn and Co compounds are isostructural: the octahedral MO6 groups share edges to form chains running parallel to the c-axis. These chains share corners (OH groups) to link into layers lying parallel to the bc plane. The hydroxyl groups do not participate in hydrogen bonds. The structure of (NH4)2BPDC consists of alternating layers of BPDC and ammonium ions lying parallel to the ab plane. Each hydrogen atom of the ammonium ions in (NH4)2BPDC participates in a strong N—H...O hydrogen bond.

The crystal structure of anhydrous 2,5-dhydroxyterephthalic acid, C8H6O6, was solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The published structure of 2,5-dihydroxyterephthalic acid dihydrate was also optimized. The carboxylic acid groups form strong hydrogen bonds, which form centrosymmetric rings with graph set R22(8). These hydrogen bonds link the molecules into chains along [011]. There is an intramolecular O—H...O hydrogen bond between the hydroxyl group and the carbonyl group of the carboxylic acid. The hydrogen bonding in the dihydrate is very different. Although the intramolecular hydroxy/carboxylic acid hydrogen bond is present, the water molecule acts as an acceptor to the carboxylic acid and a donor to two other oxygen atoms. The carboxylic acid groups do not interact with each other directly.

Operando powder X-ray diffraction (PXRD) is a widely employed method for the investigation of structural evolution and phase transitions in electrodes for rechargeable batteries. Due to the advantages of high brilliance and high X-ray energies, the experiments are often carried out at synchrotron facilities. It is known that the X-ray exposure can cause beam damage in the battery cell, resulting in hindrance of the electrochemical reaction. This study investigates the extent of X-ray beam damage during operando PXRD synchrotron experiments on battery materials with varying X-ray energies, amount of X-ray exposure and battery cell chemistries. Battery cells were exposed to 15, 25 or 35 keV X-rays (with varying dose) during charge or discharge in a battery test cell specially designed for operando experiments. The observed beam damage was probed by mPXRD mapping of the electrodes recovered from the operando battery cell after charge/discharge. The investigation reveals that the beam damage depends strongly on both the X-ray energy and the amount of exposure, and that it also depends strongly on the cell chemistry, i.e. the chemical composition of the electrode. [ABSTRACT FROM AUTHOR]

Antimony oxides are important materials for catalysis and flame-retardant applications. The two most common phases, α -Sb2O3 (senarmontite) and β -Sb2O3 (valentinite), have been studied extensively. Specific focus has been placed recently on their lattice dynamics properties and how they relate to the α - β phase transformation and their potential anharmonicity. However, there has not been any direct investigation of anharmonicity in these systems, and a surprising lack of low-temperature structural information has prevented further study. Here, we report the powder neutron diffraction data of both phases of Sb2O3, as well as structural information. α -Sb2O3 behaved as expected, but β -Sb2O3 revealed a small region of zero thermal expansion along the c axis. Additionally, while the β phase matched well with reported atomic displacement parameters, the α phase displayed a marked deviation. This data will enable further investigations into these systems. [ABSTRACT FROM AUTHOR]

Layered hybrid halometallates represent a promising class of multifunctional materials, yet with many open challenges regarding the interaction between building blocks. In this work, we present a synthetic and analytical methodology for the efficient synthesis and structural analysis of a series of novel tetrahalocuprate(II) hybrids based on small alkylammonium cations. Observed robustness in geometrical motifs provided a platform for crystal structure determination, even from the complex laboratory powder diffraction data. The slight differences in inorganic layer geometry and severe differences in organic bilayer packing are quantified using well-established descriptors for these materials, and dependences of geometric parameters on anion and cation choice are accounted for. Temperature dependence of structural parameters for one of the tetrachlorocuprate hybrids that was chosen as a model unveils a possible geometrical origin of thermochromism in these materials. [ABSTRACT FROM AUTHOR]

The crystal structure of besifloxacin hydrochloride has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Besifloxacin hydrochloride crystallizes in space group P 1 (#1) with a = 5.36596(8), b = 10.3234(4), c = 17.9673(14) Å, α = 98.122(5), β = 92.9395(9), γ = 96.1135(3)°, V = 977.483(13) Å3, and Z = 2. The crystal structure is approximately centrosymmetric. Strong N–H⋯Cl hydrogen bonds form a corrugated ladder-like chain along the a -axis. The carboxylic acid group in each independent cation acts as the donor in a strong intramolecular O–H⋯O hydrogen bond to an adjacent carbonyl group. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

The crystal structure of butenafine hydrochloride has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Butenafine hydrochloride crystallizes in space group P 21 (#4) with a = 13.94807(5), b = 9.10722(2), c = 16.46676(6) Å, β = 93.9663(5)°, V = 2086.733(8) Å3, and Z = 4. Butenafine hydrochloride occurs as a racemic co-crystal of R and S enantiomers of the cation. The crystal structure is characterized by parallel stacks of aromatic rings along the b -axis. Each cation forms a strong discrete N–H⋯Cl hydrogen bond. The chloride anions also act as acceptors in several C–H⋯Cl hydrogen bonds from methylene, methyl, and aromatic groups. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

The crystal structure of deracoxib has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Deracoxib crystallizes in space group Pbca (#61) with a = 9.68338(11), b = 9.50690(5), c = 38.2934(4) Å, V = 3525.25(3) Å3, and Z = 8. The molecules stack in layers parallel to the ab -plane. N–H⋯O hydrogen bonds link the molecules along the b -axis, in chains with the graph set C1,1(4) , as well as more-complex patterns. N–H⋯N hydrogen bonds link the layers. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

The crystal structure of elvitegravir Form II has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Elvitegravir Form II crystallizes in space group P 21 (#4) with a = 11.54842(7), b = 14.04367(5), c = 13.33333(8) Å, β = 90.0330(6)°, V = 2162.427(14) Å3, and Z = 4. The crystal structure consists of alternating layers of parallel molecules perpendicular to the b -axis. The mean planes of the oxoquinoline ring systems in molecules 1 and 2 are 1(22)-1 and -1(22)1. Between the stacks are layers of the halogenated phenyl rings. These exhibit herringbone stacking. In each molecule, the carboxylic acid group forms a strong intramolecular O–H⋯O hydrogen bond to the nearby carbonyl group. The hydroxyl group of each molecule forms a strong hydrogen bond to the carbonyl group of the carboxylic acid of the other molecule. These O–H⋯O hydrogen bonds link the molecules into dimers, with a graph set R2,2(18) > a > c. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

The crystal structure of toceranib has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Toceranib crystallizes in space group P 21/ c (#14) with a = 10.6899(6), b = 24.5134(4), c = 7.8747(4) Å, β = 107.7737(13)°, V = 1965.04(3) Å3, and Z = 4. The crystal structure consists of stacks of approximately planar molecules, with N–H⋯O hydrogen bonds between the layers. The commercial reagent sample was a mixture of two or more phases with toceranib being the dominant phase. The difference between the Rietveld-refined and DFT-optimized structures is larger than usual. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

The crystal structure of oxibendazole has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Oxibendazole crystallizes in space group C 2/ c (#15) with a = 23.18673(22), b = 5.35136(5), c = 19.88932(13) Å, β = 97.0876(9)°, V = 2449.018(17) Å3, and Z = 8. The structure consists of hydrogen-bonded layers of planar molecules parallel to the bc -plane. Strong N–H⋯N hydrogen bonds link the molecules into dimers, with a graph set R2,2(8). N–H⋯O hydrogen bonds further link these dimers into layers parallel to the bc -plane. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

The crystal structure of one form of halofuginone hydrobromide has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Halofuginone hydrobromide crystallizes in space group P2 1 (#4) with a = 8.87398(13), b = 14.25711(20), c = 15.0153(3) Å, β = 91.6867(15)°, V = 1898.87(4) Å3, and Z = 4. The crystal structure consists of alternating layers (parallel to the ab -plane) of planar and nonplanar portions of the cations. N–H⋯Br and O–H⋯Br hydrogen bonds link the protonated piperidine rings and bromide anions into a two-dimensional network parallel to the ab -plane. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®). [ABSTRACT FROM AUTHOR]

Structural analysis using powder X‐ray diffraction data has overcome many obstacles and nowadays is readily applicable for structural analysis of all types of compounds and materials. Being less straightforward than single crystal diffraction, it requires significant users' input and consequently, implementation of standardized tools to assess the accuracy of crystal structures. This article discusses potential errors in crystal structure solution and refinement of small‐molecule structures obtained from PXRD data. Moreover, it proposes how accuracy of these structures can be improved by using high‐quality PXRD data, complementary external analytical techniques, knowledge stored in crystal structure databases, as well as an approach to search the parameter space to avoid local minima in testing different sets of geometry restraints. [ABSTRACT FROM AUTHOR]

Tranexamic acid (TNA) is an anti‐fibrinolytic hemostatic drug widely used in various medical treatments. Six new salts and five cocrystals of TNA are reported here and the crystal structures of the obtained multicomponent compounds were determined using single‐crystal X‐ray diffraction (SC‐XRD) techniques. TNA formed salts with coformers maleic acid (MEA), nicotinic acid, dl‐mandelic acid and saccharin. Salt formation with MEA resulted in three different solid forms, namely TNA–MEA (1:1), TNA–MEA (2:1) and TNA–MEA–H2O (1:1:1). All synthesized TNA salt structures were crystallized as anhydrous except for TNA–MEA–H2O (1:1:1). TNA formed cocrystals with phenolic coformers such as catechol (CAT), resorcinol, hydroquinone, pyrogallol (PRG) and phloroglucinol. All cocrystal structures crystallized as hydrates except for TNA–PRG (1:1). The detailed structural investigation using SC‐XRD revealed the presence of robust N—H...O and O—H...O hydrogen bonds in TNA salts and cocrystals. In TNA cocrystals, except for TNA–CAT–H2O (1:1:1), the coformer molecules interact with TNA molecules via bridged water molecules. In all the salt structures, TNA exists as cations, in which both carboxylic and amino groups are protonated (–COOH and –NH3+), while in cocrystals TNA exists as zwitterions with total charge zero. All synthesized multicomponent compounds were further characterized by differential scanning calorimetric, thermogravimetric and Fourier transform infrared analyses, and the formation of new multicomponent compounds were assessed based on the melting temperatures, percentage weight loss and stretching frequencies, respectively, corresponding to TNA/coformer molecules. A powder X‐ray diffraction study confirmed the bulk purity of the synthesized crystalline multicomponent compounds. [ABSTRACT FROM AUTHOR]

Nanocomposites of methacrylate-based polyhedral oligomeric silsesquioxane (POSS) are used as resins in dentistry to fill dental cavities. In this article, molecular dynamics simulations (MDS) are used to study and understand the interactions of monofunctional and multifunctional methacrylate groups on hybrid resins containing POSS additives for dental applications. These interactions are further related to the structural properties of the nanocomposites, which in turn affect their macro-properties that are important, especially when used for specific uses such as dental resins. For monofunctional methacrylate, nanocomposite of methacryl isobutyl POSS (MIPOSS) and for multifunctional methacrylate, methacryl POSS (MAPOSS) are used in this study. Molecular dynamic simulations (MDS) are performed on both MIPOSS and MAPOSS systems by varying the amount of POSS. On a weight percent basis, 1%, 3%, 5%, and 10% POSS are added to the resin. Density calculations, stress–strain, and powder diffraction simulations are used to evaluate the macro-properties of these nanocomposites and compare them with the experimental findings reported in the literature. The observations from the simulation results when compared to the experimental results show that MDS can be efficiently used to design, analyze, and simulate new nanocomposites of POSS. [ABSTRACT FROM AUTHOR]

Abstract The complexes of type [Ni(L1/L2 )(PPh3)2/dppe]NO3 (1a-4a) and [Zn(L1/L2 )(PPh3)2/(dppe)]NO3 (1b-4b) [where L1  = 2-((E)-(4-(2-(trimethylsilyl)ethynyl)phenylimino)methyl)-4-(2-(4-bromophenyl)ethynyl) phenol; L2  = 2-((E)-(4-(2-(trimethylsilyl)ethynyl)phenylimino)methyl)-4-(2-(4-methoxyphenyl)ethynyl) phenol; PPh3 = triphenylphosphine; and dppe = 1, 2-bis(diphenylphosphino)ethane] have been synthesized and characterized by elemental analyses, IR, UV–Vis, 1H NMR, and 31P NMR spectral studies. The ancillary phosphine ligands significantly perturb the metal to ligand charge transfer (MLCT) state of Ni(II) and Zn(II) complexes and associated with their electron donating character. The room temperature luminescence is observed for all complexes which corresponds to π→π* ILCT transition with some MLCT character. The second harmonic generation (SHG) efficiency of the complexes was determined by Kurtz-powder technique indicating that all complexes displayed the SHG property. Metal oxide nanoparticles were obtained by calcinations of representative complexes 1a and 4b at 600 °C and are characterized by FTIR, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction techniques. [ABSTRACT FROM AUTHOR]