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Application of synchrotron through-the-substrate microdiffraction to crystals in polished thin sections.

Rius J, Vallcorba O, Frontera C, Peral I, Crespi A, Miravitlles C - IUCrJ (2015)

Bottom Line: Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed.The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples).Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Ciència de Materials de Barcelona, CSIC, Campus de la Universitat Autònoma de Barcelona, Bellaterra, Catalonia 08193, Spain.

ABSTRACT
The synchrotron through-the-substrate X-ray microdiffraction technique (tts-μXRD) is extended to the structural study of microvolumes of crystals embedded in polished thin sections of compact materials [Rius, Labrador, Crespi, Frontera, Vallcorba & Melgarejo (2011 ▸). J.Synchrotron Rad. 18, 891-898]. The resulting tts-μXRD procedure includes some basic steps: (i) collection of a limited number of consecutive two-dimensional patterns (frames) for each randomly oriented crystal microvolume; (ii) refinement of the metric from the one-dimensional diffraction pattern which results from circularly averaging the sum of collected frames; (iii) determination of the reciprocal lattice orientation of each randomly oriented crystal microvolume which allows assigning the hkl indices to the spots and, consequently, merging the intensities of the different frames into a single-crystal data set (frame merging); and (iv) merging of the individual crystal data sets (multicrystal merging) to produce an extended data set suitable for structure refinement/solution. Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed. The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples). Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

No MeSH data available.


Related in: MedlinePlus

Diopside-(Fe). A perspective view of the unit cell along the c direction, as obtained from δ recycling PFDM. The tetrahedrally coordinated Si atoms (T site) and the O atoms (small spheres) form the pyroxene chains (upper view). The octahedrally coordinated atoms at M1 are mainly Mg and the eightfold coordinated atoms at M2 are principally Ca.
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fig5: Diopside-(Fe). A perspective view of the unit cell along the c direction, as obtained from δ recycling PFDM. The tetrahedrally coordinated Si atoms (T site) and the O atoms (small spheres) form the pyroxene chains (upper view). The octahedrally coordinated atoms at M1 are mainly Mg and the eightfold coordinated atoms at M2 are principally Ca.

Mentions: To check the accuracy of the unit-cell parameters derived from the one-dimensional pattern, the unit-cell parameters and the sample-to-detector distance were further refined with equations (5) and (6) by introducing five reflections per pattern (hkl indices plus p coordinates for each spot). The new parameters were a = 9.7354 (4), b = 8.9109 (6), c = 5.2451 (3) Å and β = 106.385 (1)° (V = 436.54 Å3; sample-to-detector distance = 189.42 mm). A rotation search with this new unit cell gave nearly coincident results for all crystals. The individual values of this second search and of the subsequent multicrystal merging are listed in Table 2 ▸. The merged data set contains 113 independent intensity data. Since the total number of unique reflections at this resolution is 198, it represents a data completeness of 57.07%. Despite being incomplete, application of δ recycling PFDM to this data set solved the structure (three solutions out of 25 trials) (Fig. 5 ▸).


Application of synchrotron through-the-substrate microdiffraction to crystals in polished thin sections.

Rius J, Vallcorba O, Frontera C, Peral I, Crespi A, Miravitlles C - IUCrJ (2015)

Diopside-(Fe). A perspective view of the unit cell along the c direction, as obtained from δ recycling PFDM. The tetrahedrally coordinated Si atoms (T site) and the O atoms (small spheres) form the pyroxene chains (upper view). The octahedrally coordinated atoms at M1 are mainly Mg and the eightfold coordinated atoms at M2 are principally Ca.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491317&req=5

fig5: Diopside-(Fe). A perspective view of the unit cell along the c direction, as obtained from δ recycling PFDM. The tetrahedrally coordinated Si atoms (T site) and the O atoms (small spheres) form the pyroxene chains (upper view). The octahedrally coordinated atoms at M1 are mainly Mg and the eightfold coordinated atoms at M2 are principally Ca.
Mentions: To check the accuracy of the unit-cell parameters derived from the one-dimensional pattern, the unit-cell parameters and the sample-to-detector distance were further refined with equations (5) and (6) by introducing five reflections per pattern (hkl indices plus p coordinates for each spot). The new parameters were a = 9.7354 (4), b = 8.9109 (6), c = 5.2451 (3) Å and β = 106.385 (1)° (V = 436.54 Å3; sample-to-detector distance = 189.42 mm). A rotation search with this new unit cell gave nearly coincident results for all crystals. The individual values of this second search and of the subsequent multicrystal merging are listed in Table 2 ▸. The merged data set contains 113 independent intensity data. Since the total number of unique reflections at this resolution is 198, it represents a data completeness of 57.07%. Despite being incomplete, application of δ recycling PFDM to this data set solved the structure (three solutions out of 25 trials) (Fig. 5 ▸).

Bottom Line: Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed.The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples).Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Ciència de Materials de Barcelona, CSIC, Campus de la Universitat Autònoma de Barcelona, Bellaterra, Catalonia 08193, Spain.

ABSTRACT
The synchrotron through-the-substrate X-ray microdiffraction technique (tts-μXRD) is extended to the structural study of microvolumes of crystals embedded in polished thin sections of compact materials [Rius, Labrador, Crespi, Frontera, Vallcorba & Melgarejo (2011 ▸). J.Synchrotron Rad. 18, 891-898]. The resulting tts-μXRD procedure includes some basic steps: (i) collection of a limited number of consecutive two-dimensional patterns (frames) for each randomly oriented crystal microvolume; (ii) refinement of the metric from the one-dimensional diffraction pattern which results from circularly averaging the sum of collected frames; (iii) determination of the reciprocal lattice orientation of each randomly oriented crystal microvolume which allows assigning the hkl indices to the spots and, consequently, merging the intensities of the different frames into a single-crystal data set (frame merging); and (iv) merging of the individual crystal data sets (multicrystal merging) to produce an extended data set suitable for structure refinement/solution. Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed. The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples). Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

No MeSH data available.


Related in: MedlinePlus