Precision Lattice-Parameter Determination of (Mg,Fe)SiO 3 Tetragonal Garnets

Autor:	Hiroshi Sawamoto, Satoshi Tanaka, Hideo Toraya, Rie Matsubara
Rok vydání:	1990
Předmět:	Crystallography Tetragonal crystal system Multidisciplinary Lattice constant Chemistry Lattice (order) Pyroxene Crystal structure Angstrom Mole fraction Powder diffraction
Zdroj:	Science. 247:697-699
ISSN:	1095-9203 0036-8075
DOI:	10.1126/science.247.4943.697
Popis:	The tetragonal garnet (Mg,Fe)SiO(3) is a high-pressure phase of pyroxene that is thought to be a major constituent of the earth's upper mantle. Its crystal structure is similar to that of cubic garnet, but it is slightly distorted to tetragonal symmetry so that its x-ray powder diffraction pattern shows a very small line splitting. A suite of tetragonal garnets with different compositions in the MgSiO(3)-rich portion of the MgSiO(3)-FeSiO(3) system was synthesized at about 20 gigapascals and 2000 degrees C. The lattice parameters a and c of quenched samples were determined by whole-powder-pattern decomposition analysis of Fe Kalpha x-ray powder diffraction data, which has the capacity to resolve to a high degree heavily overlapping reflections. It was found that the lattice parameters can be obtained from the following equations; a (in angstroms) = 11.516 + 0.088x and c (in angstroms) = 11.428 + 0.157x, where x, teh mole fraction of FeSiO(3), is 0.0/= x/= 0.2.
Databáze:	OpenAIRE
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