Limits...
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

(a) Axinite. Photomicrograph showing one representative measured point (arrow) in the middle of the triangle, contoured by green epidote crystals. (b) Model-free whole-pattern refinement with the observed pattern (dots), the calculated one (line) and their difference (bottom). The observed pattern corresponds to the circular average of the sum of collected two-dimensional patterns.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4491317&req=5

fig8: (a) Axinite. Photomicrograph showing one representative measured point (arrow) in the middle of the triangle, contoured by green epidote crystals. (b) Model-free whole-pattern refinement with the observed pattern (dots), the calculated one (line) and their difference (bottom). The observed pattern corresponds to the circular average of the sum of collected two-dimensional patterns.

Mentions: Axinite is a triclinic complex silicate with the unit-cell formula Ca4X2Al4[Si8B2O30](OH)2 (space group ). It contains the borosilicate anion [Si8B2O30]22−, with X being Fe2+, Mn2+ and even Mg2+ (Fig. 7 ▸). The studied specimen comes from an epidote–pyroxene–axinite pneu­mato­litic outcrop close to Pont de Suert (Catalonia, Spain) (Fig. 8 ▸a). EMP analyses (excluding boron) at nine points of several axinite crystals showed a small dispersion. By scaling the Si atomic content to eight sites in the unit cell, the cationic composition is Si8.00 (5)Ca3.94 (13)Al3.83 (6)Fe1.04 (9)Mn0.41 (3)Mg0.65 (4).


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)

(a) Axinite. Photomicrograph showing one representative measured point (arrow) in the middle of the triangle, contoured by green epidote crystals. (b) Model-free whole-pattern refinement with the observed pattern (dots), the calculated one (line) and their difference (bottom). The observed pattern corresponds to the circular average of the sum of collected two-dimensional patterns.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig8: (a) Axinite. Photomicrograph showing one representative measured point (arrow) in the middle of the triangle, contoured by green epidote crystals. (b) Model-free whole-pattern refinement with the observed pattern (dots), the calculated one (line) and their difference (bottom). The observed pattern corresponds to the circular average of the sum of collected two-dimensional patterns.
Mentions: Axinite is a triclinic complex silicate with the unit-cell formula Ca4X2Al4[Si8B2O30](OH)2 (space group ). It contains the borosilicate anion [Si8B2O30]22−, with X being Fe2+, Mn2+ and even Mg2+ (Fig. 7 ▸). The studied specimen comes from an epidote–pyroxene–axinite pneu­mato­litic outcrop close to Pont de Suert (Catalonia, Spain) (Fig. 8 ▸a). EMP analyses (excluding boron) at nine points of several axinite crystals showed a small dispersion. By scaling the Si atomic content to eight sites in the unit cell, the cationic composition is Si8.00 (5)Ca3.94 (13)Al3.83 (6)Fe1.04 (9)Mn0.41 (3)Mg0.65 (4).

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