X-ray single-crystal structure refinement of an OH-rich topaz from Sulu UHP terrane (Eastern China) Structural foundation of the correlation between cell parameters and fluorine content

2003 ◽  
Vol 15 (5) ◽  
pp. 875-881 ◽  
Author(s):  
Augusta Alberico ◽  
Simona Ferrando ◽  
Gabriella Ivaldi ◽  
Giovanni Ferraris
Keyword(s):  
Crystal Structure ◽  
Structural Foundation ◽  
Single Crystal ◽  
Structure Refinement ◽  
Eastern China ◽  
Fluorine Content ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
X Ray ◽  
Cell Parameters

scholarly journals Recommended X-ray single-crystal structure refinement and Rietveld refinement procedure for tremolite

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Paolo Ballirano ◽  
Beatrice Celata ◽  
Alessandro Pacella ◽  
Ferdinando Bosi
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Rietveld Refinement ◽  
Structure Refinement ◽  
Point Of View ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
Statistical Point ◽  
X Ray ◽  
Refinement Procedure

A detailed description of the structure of the amphibole-supergroup minerals is very challenging owing to their complex chemical composition that renders the process of cation partition extremely difficult, particularly because of the occurrence of multivalent elements. Since amphiboles naturally occur under a fibrous morphology and have largely been used to produce asbestos, there is a growing demand for detailed and accurate structural data in order to study the relationships between structure, composition and toxicity. The present study proposes a recommended refinement procedure for both X-ray single-crystal structure refinement (SREF) and Rietveld analysis for tremolite, selected as a test case. The corresponding structural results are compared to estimate the `degree of confidence' of the Rietveld refinement with regard to SREF. In particular, it is shown that the interpretation of the electron density of the tremolite structure by SREF is model dependent. By assuming that the site-scattering values from SREF should be as close as possible to those from electron microprobe analysis, as a crucial constraint for the correct description of the final crystal-chemical model, it is found that it is best satisfied by using partially ionized scattering curves (SCs) for O and Si, and neutral SCs (neutral oxygen curves or NOCs) for other atoms. This combination leads to the best fit to the diffraction data. Moreover, it is found that Rietveld refinement using NOCs produces the best structural results, in excellent agreement with SREF. It is worth noting that, due to the complexity of the diffraction pattern and the fairly large number of freely refinable parameters, refinements with different combinations of SCs produce results almost indistinguishable from a statistical point of view, albeit showing significant differences from a structural point of view.

Notizen: Single-Crystal Structure Refinement of LiZnAs

1993 ◽  
Vol 48 (5) ◽  
pp. 683-684 ◽  
Author(s):  
Wolfgang Hönle
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Refinement ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
X Ray ◽  
Zinc Blende ◽  
Ray Methods

The crystal structure of LiZnAs has been verified with single crystal X-ray methods. LiZnAs crystallizes in a filled-up zinc blende type of structure (F 43 m, a = 593.9(1) pm, As at site 4a (000); Zn at site 4d (3/4 3/4 3/4); Li at site 4 c (1/4 1/4 1/4); 25 hkl; R = 0.018). As is coordinated by 4 Li and 4 Zn atoms with identical distances of 257.2(1) pm. Li and Zn atoms are tetrahedrally coordinated by As. No indications for a disorder between Li and Zn have been found.

Potassic-magnesio-arfvedsonite, KNa2(MgFe2+Fe3+)5Si8O22(OH)2: mineral description and crystal chemistry

2018 ◽  
Vol 83 (03) ◽  
pp. 465-472 ◽  
Author(s):  
Momchil Dyulgerov ◽  
Roberta Oberti ◽  
Bernard Platevoet ◽  
Milen Kadiyski ◽  
Ventzislav Rusanov
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Trace Element ◽  
Structure Refinement ◽  
Trace Element Analysis ◽  
Single Crystal Structure ◽  
Trace Element Distribution ◽  
Crystal Structure Refinement ◽  
Element Analysis ◽  
Cell Parameters

AbstractThe complete mineral description of potassic-magnesio-arfvedsonite, a recently approved (IMA2016-083) new species of the amphibole supergroup is provided using electron microprobe analysis (EMPA), laser ablation inductively coupled plasma mass spectrometry, single-crystal structure refinement, Mössbauer and Raman spectroscopy, as well as measurement of optical and physical properties. The holotype material was found in syenitic and granitic dyke rocks in association with quartz, potassium feldspar and aegirine–augite from the Buhovo–Seslavtsi pluton, Bulgaria. Potassic-magnesio-arfvedsonite is monoclinic C2/m, with unit-cell parameters: a = 9.9804(11), b = 18.0127(19), c = 5.2971(6) Å, β = 104.341(2)° and V = 922.61 Å3. In transmitted plane-polarised light (λ = 590 cm–1), potassic-magnesio-arfvedsonite is pleochroic: X = yellow pale-green, Y = green and Z = dark-violet brown. It is biaxial (–), α = 1.645(2), β = 1.655(2), γ = 1.660(2) and 2Vmeas. = 60° and 2Vcalc. = 70°. The empirical unit formula obtained from EMPA and structure refinement is A(K0.86Na0.0.08)0.94B(Na1.74Ca0.25 Mn2+0.01)2.00C(Mg2.67Fe2+1.42Fe3+0.76Ti0.12Mn2+0.03)5.00TSi8O22W(OH1.58F0.22O0.20)2.00. The Fe3+/Fetot ratio (0.35) is consistent with both the Mössbauer spectra and the single-crystal structure refinement. The 10 strongest X-ray powder reflections [d values (in A°), I, (hkl)] are: 8.519, 80.5, (110); 3.402, 67.3, (131); 3.295, 41.0, (240); 3.173, 65.0, (310); 2.752, 35.6, ($\bar{3}$31); 2.715, 100.0 (151); 2.591, 44.1, (061); 2.542, 73.2, ($\bar{2}$02); 2.348, 38.5, ($\bar{3}$51); 2.174, 42.0, (261). Potassic-magnesio-arfvedsonite is the product of strongly peralkaline and potassic (perpotassic) magma compositions. Trace-element analysis shows that this amphibole did not exert significant control on trace-element distribution in the crystallising peralkaline magma.

X-ray single-crystal structure refinement of the 129 K superconductor HgxPb1−xBa2Ca3Cu4O10+δ

1995 ◽  
Vol 243 (1-2) ◽  
pp. 10-18 ◽  
Author(s):  
H. Schwer ◽  
J. Karpinski ◽  
K. Conder ◽  
L. Lesne ◽  
C. Rossel ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Refinement ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
X Ray

Neue Niob- und Tantalchloride der Zusammensetzung A4[M6Cl18] (A = (Ga,) In, TI; M = Nb, Ta) / New Niobium and Tantalum Chlorides of the Composition A4[M6Cl18] (A = (Ga,) In, TI; M = Nb, Ta)

1995 ◽  
Vol 50 (9) ◽  
pp. 1373-1376 ◽  
Author(s):  
Béla Baján ◽  
H.-Jürgen Meyer
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
General Formula ◽  
Coordination Sphere ◽  
Structure Refinement ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
Space Group ◽  
X Ray ◽  
New Compounds

AbstractThe syntheses of new compounds of the general formula A4[Nb6Cl18] (A = Ga, In, Tl) and A4[Ta6Cl18] (A = In, Tl) are reported. The indexing of their X-ray powder patterns was performed isotypically with K4Nb6Cl18]- A single-crystal structure refinement on In4[Ta6Cl18] gave the space group C2/m, Z - 2, a = 1077.7(3) pm, b = 1542.3(5) pm, c = 960.2(2) pm, β = 117.68(2) . The structure contains [Ta6Cl12Cl6]4- ions linked via I+ ions . In+ is situated in a strongly distorted coordination sphere of Cl- .

Iron in kornerupine; a57Fe Moessbauer spectroscopic study and comparison with single-crystal structure refinement

1999 ◽  
Vol 84 (4) ◽  
pp. 536-549 ◽  
Author(s):  
Edward S. Grew ◽  
Guenther J. Redhammer ◽  
Georg Amthauer ◽  
Mark A. Cooper ◽  
Frank C. Hawthorne ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Spectroscopic Study ◽  
Structure Refinement ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement
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