One hundred years of diffuse scattering

Welberry, T. R.; Weber, Thomas

doi:10.1080/0889311x.2015.1046853

Cited by 99 publications

(82 citation statements)

References 279 publications

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“…80 We are not aware of any published single-crystal scattering patterns (either X-ray or neutron) for LaMnO 3 within the orbital disorder regime, and the collection of such data was beyond the scope of our own study. Nevertheless the qualitative form of structured diffuse scattering anticipated for different orbital disorder models is straightforwardly calculated and may be of use in future investigations.…”

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confidence: 99%

Local structure study of the orbital order/disorder transition inLaMnO3

et al. 2017

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We use a combination of neutron and X-ray total scattering measurements together with pair distribution function (PDF) analysis to characterise the variation in local structure across the orbital order-disorder transition in LaMnO3. Our experimental data are inconsistent with a conventional order-disorder description of the transition, and reflect instead the existence of a discontinuous change in local structure between ordered and disordered states. Within the orbital-ordered regime, the neutron and X-ray PDFs are best described by a local structure model with the same local orbital arrangements as those observed in the average (long-range) crystal structure. We show that a variety of meaningfully-different local orbital arrangement models can give fits of comparable quality to the experimental PDFs collected within the disordered regime; nevertheless, our data show a subtle but consistent preference for the anisotropic Potts model proposed in Phys Rev. B 79, 174106 (2009). The key implications of this model are electronic and magnetic isotropy together with the loss of local inversion symmetry at the Mn site. We conclude with a critical assessment of the interpretation of PDF measurements when characterising local symmetry breaking in functional materials.

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confidence: 99%

Local structure study of the orbital order/disorder transition inLaMnO3

et al. 2017

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“…First characterized using simple ionic crystals in early studies of X-ray diffraction (Lonsdale, 1942), DS has a rich history (Welberry & Weber, 2016) and is a well established technique in smallmolecule crystallography (Welberry, 2004). DS studies in macromolecular crystallography began more recently (Phillips et al, 1980) and now the potential for obtaining information about protein motions is fueling the growing interest in DS (Meisburger et al, 2017).…”

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Interactions that know no boundaries

Wall

2018

Int Union Crystallogr J

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Deviations from an ideal crystal lead to diffuse scattering (DS) intensity, both between and beneath the Bragg peaks in diffraction patterns (Guinier, 1963). First characterized using simple ionic crystals in early studies of X-ray diffraction (Lonsdale, 1942), DS has a rich history (Welberry & Weber, 2016) and is a well established technique in smallmolecule crystallography (Welberry, 2004). DS studies in macromolecular crystallography began more recently (Phillips et al., 1980) and now the potential for obtaining information about protein motions is fueling the growing interest in DS (Meisburger et al., 2017).As noted in a previous IUCrJ commentary ( Keen, 2016), accurate modeling of smallmolecule DS requires not only information about the variations of individual molecules or unit cells, but also information about the correlated variations in a more extended environment. Similarly, macromolecular DS studies indicate the importance of modeling interactions across unit-cell boundaries in normal-modes models (Riccardi et al., 2010), as well as the molecular dynamics models (Wall, 2018) of macromolecular diffuse scattering that are shown in this issue. The liquid-like motions (LLM) model (Caspar et al., 1988), in which the correlated variations are modeled as if the crystal were a soft homogeneous material, explains the overall DS pattern in several protein crystals (Caspar et al., 1988;Clarage et al., 1992;Van Benschoten et al., 2016;Wall, Clarage & Phillips, 1997;Wall, Ealick & Gruner, 1997). However, the consequences of including intermolecular interactions for the accuracy of the LLM model were not clear until now.In this issue, Peck and co-workers (Peck et al., 2018) investigate the importance of intermolecular interactions by assessing the accuracy of two alternative versions of an LLM model (Caspar et al., 1988) (Fig. 1). In the original version of the model, the correlations extend across molecular boundaries (Fig. 1a). In this case, the diffuse intensity is derived from the squared crystal transform, which is sharply peaked. In a modified version of the model, correlations terminate at the molecular boundary (Fig. 1b). In this case, the diffuse intensity is derived from the squared molecular transform of the asymmetric unit (in the cases considered, a single molecule), which is continuous in reciprocal space. In both cases, the transform is blurred; shorter correlation lengths correspond to a larger scale blurring of the transform. Both models are optimized to maximize the agreement with the data, enabling a well controlled comparison.To be consistent with the state of the art (Meisburger et al., 2017), three-dimensional diffuse datasets were used for the comparison, obtained from crystalline cyclophilin A (CypA) (PDB entry 4yuo; Fraser, 2015), WrpA (PDB entry 5f51; Herrou & Crosson, 2015) and alkaline phosphatase (PDB entry 5c66; Peck et al., 2017). The CypA data were the subject of a prior DS study (Van Benschoten et al., 2016) and the others were newly analyzed for this study, providing valuable addi...

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“…I 0 is commonly known as the short-range order (SRO) component, I 1 as the 'size-effect' component, and I 2 as the Huang scattering and thermal diffuse scattering (TDS) component. Expressions for each of these diffuse components may be found in Welberry & Weber (2016). The different components depend on different lattice averages, have different variations in the reciprocal space coordinates h 1 , h 2 and h 3 , and also depend differently on the atomic scattering factors.…”

Section: Scattering Componentsmentioning

confidence: 99%

Interpretation of diffuse scattering in the high-T_csuperconductor HgBa₂CuO_4+δ

Welberry¹,

Goossens²

2016

IUCrJ

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Published diffuse X-ray scattering from the high-T c superconductor HgBa 2 CuO 4+ has been reexamined with a view to developing a model that more satisfactorily accounts for the observed patterns. The present work agrees with the previous conclusion that the doping oxygen atoms form long and isolated interstitial chains that run in both tetragonal directions. However, a distinctly different model is proposed for the accompanying displacement patterns of the atoms surrounding these linear defects. In this new model it is proposed that it is the correlated shifts of the Ba atoms along the length of the defect chains that are the primary source of the observed scattering, and that the variations of intensity in the generated diffuse streaks of scattering originate from lateral shifts of both Hg and Ba atoms away from defects. The new model yields diffraction patterns that are in much more convincing agreement with the observations than the original model.

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One hundred years of diffuse scattering

Cited by 99 publications

References 279 publications

Local structure study of the orbital order/disorder transition inLaMnO3

Local structure study of the orbital order/disorder transition inLaMnO3

Interactions that know no boundaries

Interpretation of diffuse scattering in the high-T_csuperconductor HgBa₂CuO_4+δ

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One hundred years of diffuse scattering

Cited by 99 publications

References 279 publications

Local structure study of the orbital order/disorder transition inLaMnO3

Local structure study of the orbital order/disorder transition inLaMnO3

Interactions that know no boundaries

Interpretation of diffuse scattering in the high-Tcsuperconductor HgBa2CuO4+δ

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Interpretation of diffuse scattering in the high-T_csuperconductor HgBa₂CuO_4+δ