Crystallographic procedures in the study of experimental rocks: x-ray single-crystal structure refinement of C2/c clinopyroxene from lunar 74275 high-pressure experimental basalt

1988 ◽  
Vol 39 (3-4) ◽  
pp. 187-200 ◽  
Author(s):  
S. Manoli ◽  
G. M. Molin
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystal ◽  
Structure Refinement ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
X Ray

Crystal and powder XRD data of Mg3(PO4)2-III: High-temperature and high-pressure form

1995 ◽  
Vol 10 (4) ◽  
pp. 293-295 ◽  
Author(s):  
F. Brunet ◽  
C. Chopin ◽  
A. Elfakir ◽  
M. Quarton
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Single Crystal ◽  
Diffraction Pattern ◽  
Structure Refinement ◽  
Powder Xrd ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
Pressure Form

A new diffraction pattern of the high-temperature and high-pressure polymorph Mg3(PO4)2-III (PDF 43-500) is given and indexed on the basis of a single-crystal structure refinement. It allows diffractogram indexing of the isostructural high-temperature and high-pressure form of Co3(PO4)2 (PDF 43-499).

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.

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