Diffuse scattering data acquisition techniques

Estermann, M. A.; Steurer, Walter

doi:10.1080/01411599808219193

Cited by 82 publications

(57 citation statements)

References 22 publications

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“…During a single exposure, the sample is typically rocked through an angle dω ∼0.25 • , then ω is incremented by dω and the measurement repeated. After 180/dω such exposures, enough data points have been collected to reconstruct most of reciprocal space [10] out of the the maximum value, which is given by the radius of the detector, the sample-detector distance, and λ.…”

Section: X-raymentioning

confidence: 99%

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Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

Goossens

2016

Metals

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Single-crystal diffuse scattering (SCDS) reveals detailed structural insights into materials. In particular, it is sensitive to two-body correlations, whereas traditional Bragg peak-based methods are sensitive to single-body correlations. This means that diffuse scattering is sensitive to ordering that persists for just a few unit cells: nanoscale order, sometimes referred to as "local structure", which is often crucial for understanding a material and its function. Metals and alloys were early candidates for SCDS studies because of the availability of large single crystals. While great progress has been made in areas like ab initio modelling and molecular dynamics, a place remains for Monte Carlo modelling of model crystals because of its ability to model very large systems; important when correlations are relatively long (though still finite) in range. This paper briefly outlines, and gives examples of, some Monte Carlo methods appropriate for the modelling of SCDS from metallic compounds, and considers data collection as well as analysis. Even if the interest in the material is driven primarily by magnetism or transport behaviour, an understanding of the local structure can underpin such studies and give an indication of nanoscale inhomogeneity.

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Section: X-raymentioning

confidence: 99%

“…Thus, to best investigate the diffuse scattering it is necessary to survey a large region (area or volume) of reciprocal space with low noise and high dynamic range. This is not a trivial exercise, and much effort has gone into data collection and reduction [6,[9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

Goossens

2016

Metals

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“…Cuts (also called sections) were assembled using Xcavate (Estermann & Steurer, 1998;Scheidegger et al, 2000). For the frames in each cut, intensity was normalized for beam fluctuations and any over-exposed pixels were excized (Welberry et al, 2005).…”

Section: Experimental Datamentioning

confidence: 99%

Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C₈H₆O₄

Goossens

Chan

2017

Acta Crystallogr Sect B

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Terephthalic acid (TPA, C 8 H 6 O 4 ) is an industrially important chemical, one that shows polymorphism and disorder. Three polymorphs are known, two triclinic [(I) and (II)] and one monoclinic (III). Of the two triclinic polymorphs, (II) has been shown to be more stable in ambient conditions. This paper presents models of the local order of polymorphs (I) and (II), and compares the single-crystal diffuse scattering (SCDS) computed from the models with that observed from real crystals. TPA shows relatively weak and less-structured diffuse scattering than some other polymorphic materials, but it does appear that the SCDS is less well modelled by a purely harmonic model in polymorph (I) than in polymorph (II), according to the idea that the diffuse scattering is sensitive to anharmonicity that presages a structural phase transition. The work here verifies that displacive correlations are strong along the molecular chains and weak laterally, and that it is not necessary to allow the -COOH groups to librate to successfully model the diffuse scattering -keeping in mind that the data are from X-ray diffraction and not directly sensitive to H atoms.

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“…Reciprocal planes were reconstructed using XCAVATE software. 30 Data were averaged over Laue symmetry to improve the signal-to-noise ratio and to remove the artifacts related to the gaps in the detector. Single crystals of n-nonadecane/urea were prepared by slow evaporation of a solution of urea and n-nonadecane in a mixture of ethanol and isopropyl alcohol.…”

Section: 2mentioning

confidence: 99%

Critical phenomena in higher dimensional spaces: The hexagonal-to-orthorhombic phase transition in aperiodicn-nonadecane/urea

et al. 2013

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Upon cooling, the aperiodic inclusion compound n-nonadecane/urea presents a hexagonal-to-orthorhombic group-subgroup phase transition at T cl that increases the structure's superspace dimensionality from four to five. This paper reports on pretransitional phenomena in such a high-dimensional space, generalizing the critical results previously reported at a lower dimensionality. Very high-resolution diffraction data reveal anomalously large correlation lengths along the aperiodic direction, with all correlation lengths diverging at T cl . This could be explained by low-frequency phason excitations that soften at T cl at the critical wave vector, in accordance with an increase in the critical diffuse scattering intensity. The physics of phase transitions in crystalline materials was studied extensively during the last decades of the 20th century. With respect to group-subgroup structural instabilities, the order parameters, as measures of symmetry breaking, as well as related critical phenomena, were derived and measured.

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Diffuse scattering data acquisition techniques

Cited by 82 publications

References 22 publications

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C₈H₆O₄

Critical phenomena in higher dimensional spaces: The hexagonal-to-orthorhombic phase transition in aperiodicn-nonadecane/urea

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Diffuse scattering data acquisition techniques

Cited by 82 publications

References 22 publications

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C8H6O4

Critical phenomena in higher dimensional spaces: The hexagonal-to-orthorhombic phase transition in aperiodicn-nonadecane/urea

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Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C₈H₆O₄