Accurate structure-factor measurements using high-energy synchrotron radiation: a test on cuprite, Cu<sub>2</sub>O

Lippmann, Thomas; Schneider, J. R.

doi:10.1107/s0021889899012790

Cited by 39 publications

(23 citation statements)

References 21 publications

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“…The high value of g indicates that the Ag-O bond, which is rather stiff with respect to stretching, is much looser with respect to bending. This result is consistent with diffraction measurements on Cu 2 O [25,26]. The low-frequency modes responsible for the bond bending monitored by EXAFS cannot be identified with RUMs; the translational character of the perpendicular MSRD is instead a clear indication of a distortion of the Ag 4 O tetrahedra.…”

supporting

confidence: 88%

Local Thermal Expansion in a Cuprite Structure: The Case ofAg2O

et al. 2002

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The local thermal behavior of the Ag(2)O framework structure has been studied by extended x-ray absorption fine structure. The average Ag-O nearest-neighbor distance expands upon heating, while the Ag-Ag next-nearest-neighbor distance contracts. An original implementation of the cumulant analysis shows that the Ag-O expansion is a joint effect of potential anharmonicity and geometrical deformation of the Ag(4)O basic tetrahedral units. Accordingly, the negative thermal expansion of the lattice parameter in Ag(2)O cannot be explained uniquely in terms of rigid unit modes.

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supporting

confidence: 88%

Local Thermal Expansion in a Cuprite Structure: The Case ofAg2O

et al. 2002

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“…The two crystals are from the same batch grown by chemical vapour transport deposition with chlorine gas as transport agent (Schmidt et al, 1987;Christensen, 2007). Only very low temperatures ($10 K) were used for all data collections in order to reduce systematic errors such as thermal diffuse scattering and anharmonicity, and to enhance the signal-to-noise ratio of the high-order reflections (Larsen, 1995;Iversen et al, 1997;Lippmann & Schneider, 2000;Overgaard et al, 1999;Macchi et al, 2001). The data collection in Aarhus used a four-circle Huber diffractometer equipped with an Ag-sealed X-ray tube and a scintillation point detector.…”

Section: Data Collectionmentioning

confidence: 99%

Comparative study of X-ray charge-density data on CoSb₃

Schmøkel¹,

Bjerg²,

Larsen³

et al. 2013

Acta Crystallogr A Found Crystallogr

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CoSb3 is an example of a highly challenging case for experimental charge-density analysis due to the heavy elements (suitability factor of ~0.01), the perfect crystallinity and the high symmetry of the compound. It is part of a family of host-guest structures that are potential candidates for use as high-performance thermoelectric materials. Obtaining and analysing accurate charge densities of the undoped host structure potentially can improve the understanding of the thermoelectric properties of this family of materials. In a previous study, analysis of the electron density gave a picture of covalent Co-Sb and Sb-Sb interactions together with relatively low atomic charges based on state-of-the-art experimental and theoretical data. In the current study, several experimental X-ray diffraction data sets collected on the empty CoSb3 framework are compared in order to probe the experimental requirements for obtaining data of high enough quality for charge-density analysis even in the case of very unsuitable crystals. Furthermore, the quality of the experimental structure factors is tested by comparison with theoretical structure factors obtained from periodic DFT calculations. The results clearly show that, in the current study, the data collected on high-intensity, high-energy synchrotron sources and very small crystals are superior to data collected at conventional sources, and in fact necessary for a meaningful charge-density study, primarily due to greatly diminished effects of extinction and absorption which are difficult to correct for with sufficient accuracy.

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“…Following this feasibility study, the first dedicated instrument for high-energy diffraction was commissioned by Schneider at HASYLAB in 1993 [38,39]. Within the areas of condensedmatter physics and crystallography, this has been used for a series of pioneering applications to amorphous scattering [40], diffuse scattering [41,42] and phase transformations [43,44], and for nonresonant magnetic studies [45] and charge density studies [46,47]. Studies within these fields have been continued at other hard x-ray beamlines, that emerged during the 1990s; see Table 2.1.…”

Section: Hard X-ray Work Using Synchrotron Sourcesmentioning

confidence: 99%

Methods for Mesoscale Structural Characterization

Poulsen

2004

Springer Tracts in Modern Physics

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As a motivation for introducing the 3DXRD method, this chapter contains a survey of the experimental methods conventionally used for structural characterization. The options for and limitations of studies on the mesoscale are discussed. The list of methods is not complete, but is intended to reflect the methods commonly used in materials science. This survey is followed by an account of the properties of hard x-raysdefined as x-rays with an energy of or above 50 keV -and the utilization of these at hard x-ray synchrotron beamlines. To put the development of the 3DXRD microscope into perspective, a brief account is given of the historical development of the use of such beamlines, with the prime focus initially on macroscale problems in condensed-matter physics. Electron and Optical MicroscopyThe predominant set of tools for structural characterization today belong to the family of electron microscopy (EM). Thanks to its atomic-scale resolution, transmission electron microscopy (TEM) is an indispensable tool for studies of dislocation structures, precipitates, interfaces and nanoscale structures in general [1]. Scanning electron microscopy (SEM) , on the other hand, offers relatively easy sample preparation, larger inspection areas and very userfriendly measurements, but at the cost of a spatial resolution of 1-50 nm [2].Within the last decade, SEM studies in combination with the automatic electron back-scattering pattern (EBSP) method [3,4,5,6] have become the workhorse for many metallurgical studies. The EBSP method, also known as EBSD, enables determination of the crystallographic orientation of selected local areas and reveals the microstructure by orientation contrast. When it is used in conventional SEMs, the spatial resolution is about 0.5-1 µm, whereas field-emission-gun SEMs may give resolutions as high as 50 nm [7]. A limitation for certain studies may be the angular resolution of the orientation determination, which presently is 0.5 0 -1 0 . Despite the enormous impact of EM, it is well recognized that using electrons as a probe is associated with a set of inherent disadvantages. Firstly, probing the elastic and plastic strain by EM is notoriously difficult. Secondly, the dynamical scattering processes involved complicate the process of structural refinement on the basis of diffraction data. Thirdly, the electrons penetrate ≤ 1 µm into materials, such that only the surface region is probed. This fact implies a number of limitations, which are central to this book. They are discussed in detail below.1. 2D characterization. The structural objects of interest, i.e. grains, dislocation structures, cracks, etc., are in general truly three-dimensional in nature. On the basis of observations from a single section, it is only possible to provide a 3D description by subjecting the objects to a statistical treatment. The discipline of stereology [8] was invented to facilitate such a description. However, it turns out that a number of parameters of interest simply cannot be inferred from a single 2D section without...

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Accurate structure-factor measurements using high-energy synchrotron radiation: a test on cuprite, Cu₂O

Cited by 39 publications

References 21 publications

Local Thermal Expansion in a Cuprite Structure: The Case ofAg2O

Local Thermal Expansion in a Cuprite Structure: The Case ofAg2O

Comparative study of X-ray charge-density data on CoSb₃

Methods for Mesoscale Structural Characterization

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Accurate structure-factor measurements using high-energy synchrotron radiation: a test on cuprite, Cu2O

Cited by 39 publications

References 21 publications

Local Thermal Expansion in a Cuprite Structure: The Case ofAg2O

Local Thermal Expansion in a Cuprite Structure: The Case ofAg2O

Comparative study of X-ray charge-density data on CoSb3

Methods for Mesoscale Structural Characterization

Contact Info

Product

Resources

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Accurate structure-factor measurements using high-energy synchrotron radiation: a test on cuprite, Cu₂O

Comparative study of X-ray charge-density data on CoSb₃