Application of Patterson-function direct methods to materials characterization

Rius, Jordi

doi:10.1107/s2052252514017606

Cited by 9 publications

(9 citation statements)

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“…Lincei determination by classical direct methods even when otherwise optimal data with good overall completeness were available. In such cases, solution could be anyway achieved by adopting algorithms less sensitive to missing data, like the Patterson-function d-recycling (Rius 2014), or able to include a priori information, like the zeolitespecific software FOCUS (Grosse- Kunstleve et al 1997). The complex zeolite structure IM-5 (spacegroup Cmcm, cell parameters: a = 14.2 Å , b = 57.2 Å , c = 20.0 Å , Fig.…”

Section: Inorganic Phasesmentioning

confidence: 99%

Single nano crystal analysis using automated electron diffraction tomography

Mugnaioli

2014

Rend. Fis. Acc. Lincei

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Most of hitherto unknown natural phases and many new synthetic compounds can grow only in the form of nanocrystals. X-ray powder diffraction is the most widespread technique for the structural characterization of nanomaterials, but its use is limited by two main restrictions: structural information is projected in one dimension and data come from the whole sample and not from a specific single crystallite. On the other hand, crystallographic methods based on the scattering of accelerated electrons are able to obtain 3-D structural data from single volumes of few tens of nanometers. Automated diffraction tomography is a recently developed method able to record more kinematical and complete electron diffraction data. This method consists in the acquisition of a series of electron diffraction patterns while the sample is rotated around an arbitrary tilt axis by sequential mechanical steps, within the full tilt range of the microscope goniometer. Data collection can be performed on highly beam sensitive materials, as no time is required for orienting the crystal along specific crystallographic orientations and mild illumination conditions are used. In the last years many nanocrystalline materials belonging to different material classes have been characterized by automated diffraction tomography. This review describes the different experimental and analytical approaches used for the determination of inorganic and organic phases and points out the advantages offered by automated diffraction tomography for the characterization of minor phases available only in polyphasic nanomixtures and for the description of domain arrangement in polycrystalline nanocomposites.

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Section: Inorganic Phasesmentioning

confidence: 99%

Single nano crystal analysis using automated electron diffraction tomography

Mugnaioli

2014

Rend. Fis. Acc. Lincei

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“…5). It is known that both REE and Cu 2+ can produce clusters with cubane-like core structures of type [REE 4 (µ 3 -OH) 4 ] 8+ (Plakatouras et al, 1994;Xiao-Ming et al, 1997) and [Cu 4 (µ 3 -OH) 4 ] 4+ (Dedert et al, 1982;Sletten et al, 1990). In DCP1 the cubane-like core has 3 µ 3 -OH (O8) and a chlorine atom (Cl1) replacing the fourth apical one.…”

Section: The Tetranuclear Complex: the M2 And M3 (As Well As Cu2) Sitesmentioning

confidence: 99%

“…Rius et al: Structural study of decrespignyite-(Y) and electron beam damage are those minerals based on selfassembly of metal clusters via H bond networks (León-Reina et al, 2013;Capitani et al, 2014;Ventruti et al, 2015;Majzlan et al, 2016). In such cases application of direct methods like δ recycling (δDM) (Rius, 2012a(Rius, , 2014 is more complicated since parts of the structure may not show up in the Fourier map. One such case is represented by decrespignyite-(Y), a mineral with unknown crystal structure.…”

Section: Introductionmentioning

confidence: 99%

Structural study of decrespignyite-(Y), a complex yttrium rare earth copper carbonate chloride, by three-dimensional electron and synchrotron powder diffraction

et al. 2020

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Abstract. The crystal structure of the mineral decrespignyite-(Y) from the Paratoo copper mine (South Australia) has been obtained by applying δ recycling direct methods to 3D electron diffraction (ED) data followed by Rietveld refinements of synchrotron data. The unit cell is a= 8.5462(2), c= 22.731(2) Å and V= 1437.8(2) Å3, and the chemical formula for Z=1 is (Y10.35REE1.43Ca0.52Cu5.31)Σ17.61(CO3)14Cl2.21(OH)16.79⋅18.35H2O (REE: rare earth elements). The ED data are compatible with the trigonal P3‾m1 space group (no. 164) used for the structure solution (due to the disorder affecting part of the structure, the possibility of a monoclinic unit cell cannot completely be ruled out). The structure shows metal layers perpendicular to [001], with six independent positions for Y, REE and Cu (sites M1 to M4 are full, and sites M5 and M6 are partially vacant), and two other sites, Cu1 and Cu2, partially occupied by Cu. One characteristic of decrespignyite is the existence of hexanuclear (octahedral) oxo-hydroxo yttrium clusters [Y6(μ6-O)(μ3-OH)8O24] (site M1) with the 24 bridging O atoms belonging to two sets of symmetry-independent (CO3)2− ions, with the first set (2×) along a ternary axis giving rise to a layer of hexanuclear clusters and the second set (6×) tilted and connecting the hexanuclear clusters with hetero-tetranuclear ones hosting Cu, Y and REE (M2 and M3 sites). The rest of the crystal structure consists of two consecutive M3 + M4 layers containing the partially occupied M5, M6, and Cu2 sites and additional carbonate anions in between. The resulting structure model is compatible with the chemical analysis of the type material which is poorer in Cu and richer in (REE, Y) than the above-described material.

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“…which involves in the H summation only the large E values (Rius, 2014). Q is updated at the end of each iteration (with Q ini and Q end being the discrepancies at the beginning and at the end of the second stage).…”

Section: ≠0mentioning

confidence: 99%