Rietveld refinement of a wrong crystal structure

Buchsbaum, Christian; Schmidt, Martin

doi:10.1107/s0108768107050823

Cited by 28 publications

(38 citation statements)

References 15 publications

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“…At a maximum peak height of 50,000 counts, a typical value for a detection system scaling signals in 2 16 steps, and with a linear ratio given by the scaling factors of Figure 6, LiNbO 3 :Yb-and TiO 2 -nanopowders can be easily distinguished. Furthermore, they are both well-displaced in relation to the f R = 1-line by approximately six to seven orders of magnitude.…”

Section: Discussionmentioning

confidence: 99%

“…For bulk crystals, appropriate tools were developed in the 1960s, and are successfully and widely applied in the framework of crystal growth with micro-and nanocrystalline materials. As a matter of fact, second harmonic generation (SHG)-where two pump photons are upconverted to a single photon-has been developed as an important complementary tool to XRD, especially if the structural analysis by the latter yields ambiguous results [15,16]. In the small particle limit, however, present techniques may encounter difficulties due to diminishing nonlinear harmonic efficiencies [17], especially for higher harmonics beyond the second order, thereby enforcing intensities in the PW/m 2 -region.…”

Section: Introductionmentioning

confidence: 99%

“…Mathematically, this possibility might be valid; however, from a physical point of view, this is rather unlikely. Typical spectrometers often possess a dynamic range of 2 16 values, as opposed to the approximately 2 67 values displayed in Figure 1 (left), thereby greatly reducing the likelihood of an intersection. Secondly, polar and nonpolar samples exhibit vastly different spectral characteristics with similarly large A 2ω /A 3ω -ratios, thereby reducing the chance of a false classification even further.…”

Section: Introducing a Figure Of Meritmentioning

confidence: 99%

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Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

et al. 2017

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Nonlinear diffuse femtosecond-pulse reflectometry is introduced as a powerful experimental tool for the unambiguous characterization of polar and non-polar point symmetry groups of harmonic upconversion nanoparticles. Using intense ultrashort 40 femtosecond laser pulses and an appropriate figure of merit (FOM), second and third harmonic emission serve for the structural characterization of polar Yb-doped lithium niobate and non-polar titanium dioxide nanoparticles. The tool is capable of differentiating these two samples by FOM values that differ by up to 13 orders of magnitude. The general applicability to harmonic upconversion nanoparticles over a broad range of intensities and wavelength spectrum, is discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introducing a Figure Of Meritmentioning

confidence: 99%

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Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

et al. 2017

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“…Of course, errors may also occur in structures determined from powder diffraction data, with their inherently reduced information content. A remarkable example was given by Buchsbaum & Schmidt [6]: The Rietveld refinement of the X-ray powder pattern of the g-phase of quinacridone (C 20 H 12 N 2 O 2 ) with the crystal structure of the b-phase of quinacridone gives a reasonably smooth difference curve; the resulting crystal structure looks reasonable in terms of molecular conformation, molecular packing and intermolecular hydrogen bonds. However, neither the lattice parameters, nor the molecular packing nor the conformation of the molecules shows any similarity with the actual structure, which was determined from single-crystal data.…”

Section: Introductionmentioning

confidence: 97%

The use of dispersion-corrected DFT calculations to prevent an incorrect structure determination from powder data: the case of acetolone, C₁₁H₁₁N₃O₃

Brüning¹,

Alig

Streek³

et al. 2011

Zeitschrift Für Kristallographie

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The crystal structure of acetolone (5-(acetoacetylamino)benzimidazolone, C 11 H 11 N 3 O 3 ), was determined from X-ray powder data. Despite strong preferred orientation effects, the structure could be solved with real-space methods and refined by the Rietveld method using restraints. The resulting structure gave a good Rietveld fit with reasonable confidence values; the structure looked chemically sensible and passed all tests including a CSD check and the checkCIF procedure. But dispersion-corrected density functional theory (DFT-D) calculations revealed that this structure was actually wrong, and further work showed that the terminal acetyl group had to be rotated by 180 . The correct crystal structure led to a better Rietveld refinement with improved R-values. This structure was confirmed by DFT-D calculations. The compound crystallises in P 1 1 with two molecules per unit cell. The molecules are connected by a 2-dimensional hydrogen bond network.

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“…[31] The recent development of the determination of the crystal structure by X-ray diffraction in the polycrystal yields the solution of a reliable level in most cases, with hundreds Rietveld refined small-molecule structures published each year. However, unlike X-ray diffraction in the single crystal, the discrepancy factor may be unreliable, [32] and the e.s.d. values of the structural parameters may be misleading.…”

Section: Recent Advancementmentioning

confidence: 99%

Contemporary Diffraction Methods in Study of Polycrystals

Popović¹,

Tonejc²,

Skoko³

2015

Croat. Chem. Acta

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Diffraction in the polycrystal/crystalline powder is one of the most powerful techniques in study of microstructure and crystal structure of solids. This technique enables, in synergy with microscopic, spectroscopic and other physical techniques, a complete analysis of onephase and multi-phase substances, that are important in scientific and technological fields. Information on microstructure and crystal structure of a substance is stored in its diffraction pattern; in order to reveal this information, the diffraction pattern should be decoded by application of adequate mathematical and physical procedures which may often be rather complex. During the last decades, diffraction techniques in the polycrystal are developing rapidly due to the introduction of sophisticated instrumentation, powerful computers and by application of synchrotron radiation. This advance enables the collection and interpretation of diffraction data in a short real time as well as the study of time-resolved dynamic processes in the crystalline substance. Possibilities of diffraction techniques in the polycrystal are concisely described and illustrated by examples of authors' scientific studies.Keywords: X-ray diffraction, microstructure, crystal structure, recent advancement in diffraction. DIFFRACTION IN THE POLYCRYSTALIFFRACTION is a phenomenon in which the beam of X-rays, electrons or neutrons, by passing through a single crystal or a polycrystal, deviates from the initial direction due to the scattering on the structural motifs (atoms, ions, molecules) in the crystal. The scattered waves give rise to diffraction maxima in a set of discrete space directions due to their mutual constructive interference. These directions strongly depend on the periodicity and symmetry of the crystal. The set of diffraction maxima represent the diffraction pattern of the single crystal / polycrystal. The intensities of diffraction maxima depend on the nature of structural motifs and their mutual space arrangement. Therefore, diffraction techniques are ideal in the study of the crystal structure and microstructure: space periodicity in the crystal, unit-cell parameters (unit-cell edges a, b and c and angles among them, α, β and γ), symmetry elements which determine the space group, space periodical arrangement of structural motifs, identification of particular atoms and their coordinates, definition of the nature and length of their mutual chemical bonds, the angles among the chemical bonds, the size and shape of crystallites, distribution of crystallite sizes, the nature of the crystallite / grain boundary, stresses and strains inside the crystallite, point, planar and volume defects inside the crystallite, phase transitions in a given substance and the definition of its phase diagram, etc.In determination of the crystal structure, diffraction in the single crystal has an advantage in relation to the diffraction in the polycrystal. That is a consequence of the fact that the 3D data, obtained by diffraction in the single crystal, are transferred ...

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Rietveld refinement of a wrong crystal structure

Cited by 28 publications

References 15 publications

Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

The use of dispersion-corrected DFT calculations to prevent an incorrect structure determination from powder data: the case of acetolone, C₁₁H₁₁N₃O₃

Contemporary Diffraction Methods in Study of Polycrystals

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Rietveld refinement of a wrong crystal structure

Cited by 28 publications

References 15 publications

Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

The use of dispersion-corrected DFT calculations to prevent an incorrect structure determination from powder data: the case of acetolone, C11H11N3O3

Contemporary Diffraction Methods in Study of Polycrystals

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Product

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The use of dispersion-corrected DFT calculations to prevent an incorrect structure determination from powder data: the case of acetolone, C₁₁H₁₁N₃O₃