Structure determination of Mg3(OH)5Cl·4H2O (F5 phase) from laboratory powder diffraction data and its impact on the analysis of problematic magnesia floors

2007 ◽  
Vol 63 (6) ◽  
pp. 805-811 ◽  
Author(s):  
Kunihisa Sugimoto ◽  
Robert E. Dinnebier ◽  
Thomas Schlecht
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Room Temperature ◽  
Real Life ◽  
Quantitative Phase Analysis ◽  
Binder Phase ◽  
Powder Diffraction Data ◽  
First Time

The crystal structure with the idealized formula Mg3(OH)5Cl·4H2O, the so-called F5 phase according to 5Mg(OH)2·MgCl2·8H2O in the system MgCl2–MgO–H2O, has been solved ab initio from high-quality laboratory powder diffraction data at room temperature. The F5 phase is structurally related to 3Mg(OH)2·MgCl2·8H2O (F3 form). The F5 phase consists of infinite triple chains with one Mg(OH)6 and two Mg(OH)4(OH2)2 octahedra as building units intercalated by chlorides, which are partly substituted by disordered hydroxides in the real structure. The F5 phase is of technological importance as the most important binder phase in Sorel cements. Knowledge of the crystal structure enables the full quantitative phase analysis of magnesia cements for the first time, which turns out to be very helpful in the search for possible causes of broken or bleached magnesia floors. Two real-life examples are given.

A Monte Carlo approach to crystal structure determination from powder diffraction data

2003 ◽  
Vol 36 (2) ◽  
pp. 239-243 ◽  
Author(s):  
V. Brodski ◽  
R. Peschar ◽  
H. Schenk
Keyword(s):  
Crystal Structure ◽  
Monte Carlo ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Global Minimization ◽  
Powder Diffraction Data ◽  
Unknown Structure ◽  
Space Method

A new direct-space method forab initiosolution of crystal structures from powder diffraction data is presented. The approach consists of a combined global minimization ofRwpand the potential energy of the system. This method was tested on two organic compounds with known structure and also applied successfully in the structure determination of the previously unknown structure of melamine pyrophosphate.

Ab initio structure determination of In2H2(P2O7)(P4O12) from X-ray powder diffraction data

2003 ◽  
Vol 218 (1) ◽  
Author(s):  
L. S. Ivashkevich ◽  
A. S. Lyakhov ◽  
A. F. Selevich ◽  
A. I. Lesnikovich
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Ab Initio Structure

AbstractThe crystal structure of In

Structural characterization of anhydrous and bishydrated calcium hexafluorosilicate by powder diffraction methods

2011 ◽  
Vol 26 (4) ◽  
pp. 308-312 ◽  
Author(s):  
Simone Frisoni ◽  
Stefano Brenna ◽  
Norberto Masciocchi
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Diffraction Data ◽  
Space Group ◽  
Cell Parameters ◽  
Thermal Expansion Coefficients ◽  
Full Profile ◽  
A Minor

The synthesis and X-ray powder diffraction data for the long-known CaSiF6 and CaSiF6·2H2O species are reported. Their crystal structures have been determined from laboratory powder diffraction data by simulated annealing and full-profile Rietveld refinement methods. CaSiF6·2H2O was found to crystallize in the monoclinic P21/n space group with unit-cell parameters: a = 10.48107(9), b = 9.18272(7), c = 5.72973(5) Å, β = 98.9560(6)°, V = 544.733(8) Å3, and Z = 4. The crystal structure of CaSiF6·2H2O, eventually found to be isomorphous with SrSiF6·2H2O (but not with the Mg analogue—a hexahydrate phase), contains centrosymmetric [Ca(μ-H2O)2Ca]4+ dimers, interconnected by hexafluorosilicate anions, in a dense 3D framework. The crystal structure is completed by a further water molecule, terminally bound to the Ca2+ ion, which, consequently, attains a F5O3 octacoordination. Thermodiffractometric measurements allowed the determination of the linear and volumetric thermal expansion coefficients of CaSiF6·2H2O, which showed a minor contraction, along a, on heating. CaSiF6 is trigonal, space group R-3, a = 5.3497(3), c = 13.5831(11) Å, V = 336.66(5) Å3, and Z = 3, and isomorphous with several other species of MIIAIVF6 or MIAVF6 formulation, among which several silicates, germanates, and stannates.

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