Special Issue "Crystal Structure Characterization by Powder Diffraction"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Materials".

Deadline for manuscript submissions: closed (31 December 2019).

Special Issue Editors

Dr. Angela Altomare
E-Mail Website
Guest Editor
Institute of Crystallography, National Research Council-CNR, Bari, Italy
Tel. +39 080 5929155
Interests: crystal structure solution; powder diffraction; direct methods; real space methods; indexing; space group determination; Rietveld refinement; X-ray data collection
Dr. Rosanna Rizzi
E-Mail Website
Guest Editor
Institute of Crystallography, National Research Council-CNR, Bari, Italy
Tel. +39 0805929157
Interests: crystal structure solution; powder diffraction; direct methods; real space methods; indexing; space group determination; Rietveld refinement; X-ray data collection

Special Issue Information

Dear Colleagues,

The role of powder diffraction has surprisingly increased in the last twenty-five years, and enhancements have been realized both in its earlier fields of application (e.g., qualitative analysis) and in more challenging objectives (e.g., structure solution).

In particular, microcrystalline materials of remarkable scientific and technological interest, which in the past have been unapproachable because they have not been available in the adequate form of single crystal, are nowadays widely investigated for finding out their atomic structure. The progress of the structure solution by powder diffraction data, which is well supported by the power of modern computer programs, concerns theoretical aspects, as well as applicative results.

We invite contribute of papers that, while discussing the followed computational, methodological, and/or experimental strategies, point out the essential and advanced contribution of powder diffraction in identifying the unknown crystal structure of a compound.

Potential topics include but are not limited to unit cell and space group identification; structure solution methods (reciprocal space and direct space); the Rietveld refinement method; qualitative analysis; quantitative analysis; and the crystal structure determination of organic, inorganic, and metallorganic compounds for chemistry, pharmaceutics, mineralogy, archeometry, forensic science, etc.

Dr. Angela Altomare
Dr. Rosanna Rizzi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Structure solution methods
  • Qualitative analysis
  • Quantitative analysis
  • Structure refinement
  • Structure determination

Published Papers (5 papers)

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Research

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Open AccessArticle
Co-Crystal Structures of Furosemide:Urea and Carbamazepine:Indomethacin Determined from Powder X-Ray Diffraction Data
Crystals 2020, 10(1), 42; https://doi.org/10.3390/cryst10010042 - 17 Jan 2020
Abstract
Co-crystallization is a promising approach to improving both the solubility and the dissolution rate of active pharmaceutical ingredients. Crystal structure determination from powder diffraction data plays an important role in determining co-crystal structures, especially those generated by mechanochemical means. Here, two new structures [...] Read more.
Co-crystallization is a promising approach to improving both the solubility and the dissolution rate of active pharmaceutical ingredients. Crystal structure determination from powder diffraction data plays an important role in determining co-crystal structures, especially those generated by mechanochemical means. Here, two new structures of pharmaceutical interest are reported: a 1:1 co‑crystal of furosemide with urea formed by liquid-assisted grinding and a second polymorphic form of a 1:1 co‑crystal of carbamazepine with indomethacin, formed by solvent evaporation. Energy minimization using dispersion-corrected density functional theory was used in finalizing both structures. In the case of carbamazepine:indomethacin, this energy minimization step was essential in obtaining a satisfactory final Rietveld refinement. Full article
(This article belongs to the Special Issue Crystal Structure Characterization by Powder Diffraction)
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Open AccessArticle
Solving a Structure in the Reciprocal Space, Real Space and Both by Using the EXPO Software
Crystals 2020, 10(1), 16; https://doi.org/10.3390/cryst10010016 - 31 Dec 2019
Abstract
The solution of crystal structures from X-ray powder diffraction data has undergone an intense development in the last 25 years. Overlapping, background estimate, preferred orientation are the main difficulties met in the process of determining the crystal structure from the analysis of the [...] Read more.
The solution of crystal structures from X-ray powder diffraction data has undergone an intense development in the last 25 years. Overlapping, background estimate, preferred orientation are the main difficulties met in the process of determining the crystal structure from the analysis of the one-dimensional powder diffraction pattern. EXPO is a well known computer program that, designed for solving structures, organic, inorganic, as well as metal-organic by powder diffraction data, employs the two most widely used kinds of solution methods: Direct Methods proceeding in the reciprocal space and Simulated Annealing proceeding in the real space. EXPO allows also to suitably combine these two approaches for validating the structure solution. In this paper, we give examples of structure characterization by EXPO with the aim of suggesting a solution strategy leading towards the application of reciprocal-space methods or real-space methods or both. Full article
(This article belongs to the Special Issue Crystal Structure Characterization by Powder Diffraction)
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Open AccessArticle
Boundaries of the X Phases in Sb–Te and Bi–Te Binary Alloy Systems
Crystals 2019, 9(9), 447; https://doi.org/10.3390/cryst9090447 - 29 Aug 2019
Abstract
Sb–Te and Bi–Te compounds are key components of thermoelectric or phase change recording devices. These two binary systems form commensurately/incommensurately modulated long-period layer stacking structures known as homologous phases that comprise discrete intermetallic compounds and X phases. In the latter, the homologous structures [...] Read more.
Sb–Te and Bi–Te compounds are key components of thermoelectric or phase change recording devices. These two binary systems form commensurately/incommensurately modulated long-period layer stacking structures known as homologous phases that comprise discrete intermetallic compounds and X phases. In the latter, the homologous structures are not discrete but rather appear continuously with varying stacking periods that depend on the binary composition. However, the regions over which these X phases exist have not yet been clarified. In this study, precise synchrotron X-ray diffraction analyses of various specimens were conducted. The results demonstrate that the X phase regions are located between Sb20Te3 and Sb5Te6 in the Sb–Te system and between Bi8Te3 and Bi4Te5 in the Bi–Te system. Full article
(This article belongs to the Special Issue Crystal Structure Characterization by Powder Diffraction)
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Open AccessArticle
Crystal Structure of Fosfomycin Tromethamine, (C4H12NO3)(C3H6O4P), from Synchrotron Powder Diffraction Data and Density Functional Theory
Crystals 2019, 9(8), 384; https://doi.org/10.3390/cryst9080384 - 26 Jul 2019
Abstract
The crystal structure of fosfomycin tromethamine has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Fosfomycin tromethamine crystallizes in space group P1 (#1) with a = 6.20421(6), b = 9.00072(7), c = 10.91257(15) Å, α [...] Read more.
The crystal structure of fosfomycin tromethamine has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Fosfomycin tromethamine crystallizes in space group P1 (#1) with a = 6.20421(6), b = 9.00072(7), c = 10.91257(15) Å, α = 93.4645(5), β = 101.9734(3), γ = 99.9183(2)°, V = 584.285(2) Å3, and Z = 2. A network of discrete hydrogen bonds links the cations and anions into layers parallel to the ab-plane. The outer surfaces of the layers are composed of the methyloxirane rings of the anions and the methylene groups of the cations. Furthermore, 93% of the atoms are consistent with an additional (pseudo)center of symmetry. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™. Full article
(This article belongs to the Special Issue Crystal Structure Characterization by Powder Diffraction)
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Review

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Open AccessReview
Quantitative Phase Analysis by X-ray Diffraction—Doping Methods and Applications
Crystals 2020, 10(1), 27; https://doi.org/10.3390/cryst10010027 - 07 Jan 2020
Abstract
X-ray powder diffraction is an ideal technique for the quantitative analysis of a multiphase sample. The intensities of diffraction lines of a phase in a multiphase sample are proportional to the phase fraction and the quantitative analysis can be obtained if the correction [...] Read more.
X-ray powder diffraction is an ideal technique for the quantitative analysis of a multiphase sample. The intensities of diffraction lines of a phase in a multiphase sample are proportional to the phase fraction and the quantitative analysis can be obtained if the correction for the absorption of X-rays in the sample is performed. Simple procedures of quantitative X-ray diffraction phase analysis of a multiphase sample are presented. The matrix-flushing method, with the application of reference intensities, yields the relationship between the intensity and phase fraction free from the absorption effect, thus, shunting calibration curves or internal standard procedures. Special attention is paid to the doping methods: (i) simultaneous determination of the fractions of several phases using a single doping and (ii) determination of the fraction of the dominant phase. The conditions to minimize systematic errors are discussed. The problem of overlapping of diffraction lines can be overcome by combining the doping method (i) and the individual profile fitting method, thus performing the quantitative phase analysis without the reference to structural models of particular phases. Recent suggestions in quantitative phase analysis are quoted, e.g., in study of the decomposition of supersaturated solid solutions—intermetallic alloys. Round Robin on Quantitative Phase Analysis, organized by the IUCr Commission on Powder Diffraction, is discussed shortly. The doping methods have been applied in various studies, e.g., phase transitions in titanium dioxide, biomineralization processes, and phases in intermetallic oxide systems and intermetallic alloys. Full article
(This article belongs to the Special Issue Crystal Structure Characterization by Powder Diffraction)
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