-
Journal of Synchrotron Radiation Jul 2019In situ research of materials under moderate pressures (hundreds of bar) is essential in many scientific fields. These range from gas sorption to chemical and biological...
In situ research of materials under moderate pressures (hundreds of bar) is essential in many scientific fields. These range from gas sorption to chemical and biological processes. One industrially important discipline is the hydration of oil well cements. Existing capillary cells in this pressure range are static as they are easy to design and operate. This is convenient for the study of single-phase materials; however, powder diffraction quantitative analyses for multiphase systems cannot be performed accurately as a good powder average cannot be attained. Here, the design, construction and commissioning of a cost-effective spinning capillary cell for in situ powder X-ray diffraction is reported, for pressures currently up to 200 bar. The design addresses the importance of reducing the stress on the capillary by mechanically synchronizing the applied rotation power and alignment on both sides of the capillary while allowing the displacement of the supports needed to accommodate different capillaries sizes and to insert the sample within the tube. This cell can be utilized for multiple purposes allowing the introduction of gas or liquid from both ends of the capillary. The commissioning is reported for the hydration of a commercial oil well cement at 150 bar and 150°C. The quality of the resulting powder diffraction data has allowed in situ Rietveld quantitative phase analyses for a hydrating cement containing seven crystalline phases.
Topics: Equipment Design; Powder Diffraction; Pressure; Synchrotrons; Temperature
PubMed: 31274449
DOI: 10.1107/S1600577519005150 -
Journal of Pharmaceutical Sciences Dec 2012Nortriptyline hydrochloride, a tricyclic antidepressant, appears in two different polymorphic forms, only one of which (hereafter, form β) has been previously...
Nortriptyline hydrochloride, a tricyclic antidepressant, appears in two different polymorphic forms, only one of which (hereafter, form β) has been previously characterized by single-crystal analysis. Form β is monoclinic, P2(1)/c, with a = 5.070(2), b = 34.088(5), c = 9.976(1) Å, and β = 90.74(2)°. A second crystalline form (the α form) has now been characterized by structural powder diffraction methods (using both laboratory and synchrotron radiation diffraction data). Form α crystallizes in the monoclinic P2/c space group, a = 9.99126(6), b = 5.10021(3), c = 34.1636(1) Å, and β = 98.684(6)°. The thermodynamic relationship between the two forms has been determined by differential scanning calorimetry analysis and variable-temperature thermodiffractometric experiments, revealing that the two forms are monotropically related and form α is more stable. Both phases are characterized by a sequence of hydrogen-bonded N-protonated molecules, which, in the two crystalline environments, adopt the same conformation. The difference between the two crystals can be traced back to the supramolecular arrangement characterized by one-dimensional chains, built by homochiral molecules (for conformationally driven chirality) in the α form, and by enantiomeric ones in the β form. This observation nicely explains why, upon heating, solid-solid interconversion between the two forms does not occur.
Topics: Adrenergic Uptake Inhibitors; Antidepressive Agents, Tricyclic; Calorimetry, Differential Scanning; Crystallization; Isomerism; Models, Molecular; Nortriptyline; Powder Diffraction; Thermodynamics; X-Ray Diffraction
PubMed: 22987224
DOI: 10.1002/jps.23310 -
Journal of Visualized Experiments : JoVE Nov 2014Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles....
Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles. However, many challenges, such as energy density and battery lifetimes, need to be overcome before this particular battery technology can be widely implemented in such applications. This research is challenging, and we outline a method to address these challenges using in situ NPD to probe the crystal structure of electrodes undergoing electrochemical cycling (charge/discharge) in a battery. NPD data help determine the underlying structural mechanism responsible for a range of electrode properties, and this information can direct the development of better electrodes and batteries. We briefly review six types of battery designs custom-made for NPD experiments and detail the method to construct the 'roll-over' cell that we have successfully used on the high-intensity NPD instrument, WOMBAT, at the Australian Nuclear Science and Technology Organisation (ANSTO). The design considerations and materials used for cell construction are discussed in conjunction with aspects of the actual in situ NPD experiment and initial directions are presented on how to analyze such complex in situ data.
Topics: Cations, Monovalent; Electric Power Supplies; Electrodes; Lithium; Neutron Diffraction; Powder Diffraction
PubMed: 25406578
DOI: 10.3791/52284 -
Acta Crystallographica. Section A,... Jul 2019Electron density determination based on structure factors obtained through powder X-ray diffraction has so far been limited to high-symmetry inorganic solids. This limit...
Electron density determination based on structure factors obtained through powder X-ray diffraction has so far been limited to high-symmetry inorganic solids. This limit is challenged by determining high-quality structure factors for crystalline urea using a bespoke vacuum diffractometer with imaging plates. This allows the collection of data of sufficient quality to model the electron density of a molecular system using the multipole method. The structure factors, refined parameters as well as chemical bonding features are compared with results from the high-quality synchrotron single-crystal study by Birkedal et al. [Acta Cryst. (2004), A60, 371-381] demonstrating that powder X-ray diffraction potentially provides a viable alternative for electron density determination in simple molecular crystals where high-quality single crystals are not available.
Topics: Electrons; Models, Molecular; Molecular Structure; Powder Diffraction; Quantum Theory; Urea; X-Ray Diffraction
PubMed: 31264644
DOI: 10.1107/S205327331900799X -
Acta Crystallographica. Section B,... Apr 2009The crystal structure of the nanocrystalline alpha phase of Pigment Yellow 213 (P.Y. 213) was solved by a combination of single-crystal electron diffraction and X-ray...
The crystal structure of the nanocrystalline alpha phase of Pigment Yellow 213 (P.Y. 213) was solved by a combination of single-crystal electron diffraction and X-ray powder diffraction, despite the poor crystallinity of the material. The molecules form an efficient dense packing, which explains the observed insolubility and weather fastness of the pigment. The pair-distribution function (PDF) of the alpha phase is consistent with the determined crystal structure. The beta phase of P.Y. 213 shows even lower crystal quality, so extracting any structural information directly from the diffraction data is not possible. PDF analysis indicates the beta phase to have a columnar structure with a similar local structure as the alpha phase and a domain size in column direction of approximately 4 nm.
Topics: Aza Compounds; Coloring Agents; Heterocyclic Compounds, 4 or More Rings; Microscopy, Electron, Transmission; Models, Molecular; Molecular Conformation; Particle Size; Powder Diffraction
PubMed: 19299875
DOI: 10.1107/S0108768109003759 -
Acta Crystallographica Section B,... Apr 2022A method of ab initio crystal structure determination from powder diffraction data for organic and metal-organic compounds, which does not require prior indexing of the...
A method of ab initio crystal structure determination from powder diffraction data for organic and metal-organic compounds, which does not require prior indexing of the powder pattern, has been developed. Only a reasonable molecular geometry is required, needing knowledge of neither unit-cell parameters nor space group. The structures are solved from scratch by a global fit to the powder data using the new program FIDEL-GO (`FIt with DEviating Lattice parameters - Global Optimization'). FIDEL-GO uses a similarity measure based on cross-correlation functions, which allows the comparison of simulated and experimental powder data even if the unit-cell parameters deviate strongly. The optimization starts from large sets of random structures in various space groups. The unit-cell parameters, molecular position and orientation, and selected internal degrees of freedom are fitted simultaneously to the powder pattern. The optimization proceeds in an elaborate multi-step procedure with built-in clustering of duplicate structures and iterative adaptation of parameter ranges. The best structures are selected for an automatic Rietveld refinement. Finally, a user-controlled Rietveld refinement is performed. The procedure aims for the analysis of a wide range of `problematic' powder patterns, in particular powders of low crystallinity. The method can also be used for the clustering and screening of a large number of possible structure candidates and other application scenarios. Examples are presented for structure determination from unindexed powder data of the previously unknown structures of the nanocrystalline phases of 4,11-difluoro-, 2,9-dichloro- and 2,9-dichloro-6,13-dihydro-quinacridone, which were solved from powder patterns with 14-20 peaks only, and of the coordination polymer dichloro-bis(pyridine-N)copper(II).
Topics: Copper; Polymers; Powder Diffraction; Powders
PubMed: 35411858
DOI: 10.1107/S2052520622001500 -
Organic Letters Aug 2007The current level of laboratory instrumentation and computational resources allows X-ray powder diffraction to be implemented into the toolbox of organic chemists,...
The current level of laboratory instrumentation and computational resources allows X-ray powder diffraction to be implemented into the toolbox of organic chemists, providing a means for rapid (i.e., within a day) structural characterization of organic solids, without the need for single crystals. We illustrate such use of powder diffraction using two case studies of molecular cocrystals of trifluoroacetic acid and malonic acid, involving theobromine, a model active pharmaceutical ingredient. We also report on a previously unobserved conformation of malonic acid in the solid state.
Topics: Malonates; Models, Molecular; Molecular Conformation; Molecular Structure; Powder Diffraction; Trifluoroacetic Acid; X-Ray Diffraction
PubMed: 17629292
DOI: 10.1021/ol071329t -
European Journal of Pharmaceutical... Mar 2019The direct quantification of Active Pharmaceutical Ingredients in solid formulations is a challenging open issue. A consolidated analytical technique based on X-ray...
The direct quantification of Active Pharmaceutical Ingredients in solid formulations is a challenging open issue. A consolidated analytical technique based on X-ray Powder Diffraction is available, being the definitive test for the identification of polymorphs and crystal phases. However, its application for quantitative analysis is hindered by matrix effects: refinement methods (e.g. Rietveld method) require a complete knowledge of samples' composition, while univariate calibration methods require the matrix effect to be studied and severely suffer from the co-presence of crystalline and amorphous phases in the sample. Multivariate analysis is the only way to bypass problems affecting refinements procedures and univariate calibration. In particular, the multivariate standard addition method (SAM) is promising; however, it is straightforward only when the analytical blank (matrix devoid of analyte) is available: in that case SAM is applied by simply extrapolating the SAM model to the matrix experimental signal. In this work, the quantitative analysis of polymorphic forms of Active Pharmaceutical Ingredients based on X-ray Powder Diffraction is performed for the first time by a method based on multivariate standard addition method combined with net analyte signal procedure; it allows for reliable quantification of polymorphs of active principles in solid formulations, which are rapidly analyzed without any sample pre-treatment. Two test cases are presented: quantification of two polymorphs of piracetam in binary mixtures (forms II and III), and quantification of paracetamol (form I) in Tachifludec®.
Topics: Acetaminophen; Analgesics, Non-Narcotic; Drug Compounding; Multivariate Analysis; Neuroprotective Agents; Piracetam; Powder Diffraction; X-Ray Diffraction
PubMed: 30654113
DOI: 10.1016/j.ejps.2019.01.014 -
Annales Pharmaceutiques Francaises Mar 2024Doxepin hydrochloride, a versatile pharmaceutical compound, has been the subject of extensive research aimed at elucidating its crystal structure and solid-state...
Doxepin hydrochloride, a versatile pharmaceutical compound, has been the subject of extensive research aimed at elucidating its crystal structure and solid-state characteristics. In this manuscript, we explore the significance of high-quality powder diffraction data in unveiling the intricate details of doxepin hydrochloride's crystal lattice. By examining the refined atom coordinates, density functional theory (DFT) optimization, and intermolecular interactions, we gain valuable insights into its structural conformation. This knowledge highlights the importance of precise crystallographic data in advancing our understanding of complex compounds and their pharmaceutical applications.
Topics: Powder Diffraction; Doxepin; Pharmaceutical Preparations
PubMed: 37884079
DOI: 10.1016/j.pharma.2023.10.007 -
Acta Crystallographica. Section D,... Jun 2013A series of bovine insulin samples were obtained as 14 polycrystalline precipitates at room temperature in the pH range 5.0-7.6. High-resolution powder X-ray diffraction...
A series of bovine insulin samples were obtained as 14 polycrystalline precipitates at room temperature in the pH range 5.0-7.6. High-resolution powder X-ray diffraction data were collected to reveal the T6 hexameric insulin form. Sample homogeneity and reproducibility were verified by additional synchrotron measurements using an area detector. Pawley analyses of the powder patterns displayed pH- and radiation-induced anisotropic lattice modifications. The pronounced anisotropic lattice variations observed for T6 insulin were exploited in a 14-data-set Rietveld refinement to obtain an average crystal structure over the pH range investigated. Only the protein atoms of the known structure with PDB code 2a3g were employed in our starting model. A novel approach for refining protein structures using powder diffraction data is presented. In this approach, each amino acid is represented by a flexible rigid body (FRB). The FRB model requires a significantly smaller number of refinable parameters and restraints than a fully free-atom refinement. A total of 1542 stereochemical restraints were imposed in order to refine the positions of 800 protein atoms, two Zn atoms and 44 water molecules in the asymmetric unit using experimental data in the resolution range 18.2-2.7 Å for all profiles.
Topics: Animals; Anisotropy; Cattle; Hydrogen-Ion Concentration; Insulin; Insulin, Ultralente; Models, Molecular; Molecular Structure; Powder Diffraction; X-Ray Diffraction
PubMed: 23695242
DOI: 10.1107/S0907444913003867