Absolute Structure Determination in Absence of Heavy Scatterers

Grochowski, J.

doi:10.12693/aphyspola.91.745

Cited by 2 publications

(1 citation statement)

References 32 publications

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“…The parameter is then considered as variable during the least-squares refinement of the crystal structure, alongside the atomic coordinates. In those cases in which the basic crystal structure is known and only the inversion domain is to be determined, similar to the case that we present here, other approaches have sought to restrict the measurement to those reflection pairs for which the discrepancy from the Friedel law is more pronounced (Page et al, 1990;Grochowski, 1997;Grochowski & Serda, 1997). Unfortunately, these methods presuppose collecting the intensities of reflections opposite to each other from the same scattering volume, which may not be feasible in crystals whose thickness is several mm, due to beam attenuation; even in the case of small crystals, the refinement required by Flack & Bernardinelli (1999) relies on an often subtle contrast between diffraction intensities in different geometries, that may be influenced by shape effects and be susceptible to systematic errors due to absorption or anisotropic extinction.…”

Section: Introductionmentioning

confidence: 99%

Identification of inversion domains in KTiOPO₄viaresonant X-ray diffraction

et al. 2015

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A novel method is presented for the identification of the absolute crystallographic structure in multi-domain polar materials such as ferroelectric KTiOPO 4 . Resonant (or 'anomalous') X-ray diffraction spectra collected across the absorption K edge of Ti (4.966 keV) on a single Bragg reflection demonstrate a huge intensity ratio above and below the edge, providing a polar domain contrast of $270. This allows one to map the spatial domain distribution in a periodically inverted sample, with a resolution of $1 mm achieved with a microfocused beam. This non-contact, non-destructive technique is well suited for samples of large dimensions (in contrast with traditional resonant X-ray methods based on diffraction from Friedel pairs), and its potential is particularly relevant in the context of physical phenomena connected with an absence of inversion symmetry, which require characterization of the underlying absolute atomic structure (such as in the case of magnetoelectric coupling and multiferroics).

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Section: Introductionmentioning

confidence: 99%

Identification of inversion domains in KTiOPO₄viaresonant X-ray diffraction

et al. 2015

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Reporting and evaluating absolute-structure and absolute-configuration determinations

2000

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Detailed practical and numerical information is provided for undertaking and evaluating absolute-structure and absolute-con®guration determinations. The interpretation of numerical values of x, the Flack [Acta Cryst. (1983), A39, 876± 881] parameter, and its standard uncertainty u are explained in terms of the inversion-distinguishing power. Moreover, the conditions to obtain reliable values of x(u) are detailed. Further explanatory material is provided on the use of right-handed axes, valid intensity data, the application to macromolecular structures, the dangers of polar-dispersion errors, Euclidean normalizers of space groups, the detection and reporting of molecular symmetry, enantiopurity and optical activity in solution. New CIF data names are introduced.

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Absolute Structure Determination in Absence of Heavy Scatterers

Cited by 2 publications

References 32 publications

Identification of inversion domains in KTiOPO₄viaresonant X-ray diffraction

Identification of inversion domains in KTiOPO₄viaresonant X-ray diffraction

Reporting and evaluating absolute-structure and absolute-configuration determinations

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Absolute Structure Determination in Absence of Heavy Scatterers

Cited by 2 publications

References 32 publications

Identification of inversion domains in KTiOPO4viaresonant X-ray diffraction

Identification of inversion domains in KTiOPO4viaresonant X-ray diffraction

Reporting and evaluating absolute-structure and absolute-configuration determinations

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Product

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Identification of inversion domains in KTiOPO₄viaresonant X-ray diffraction

Identification of inversion domains in KTiOPO₄viaresonant X-ray diffraction