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Crystalline post-quartz phase in silica at high pressure
J Haines1, J M Léger, F Gorelli
1Laboratoire de Physico-Chimie de la Matière Condensée, UMR CNRS 5617, Université Montpellier II Sciences et Techniques du Languedoc, cc 003, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
Physical Review Letters
|October 3, 2001
Summary
Alpha-quartz transforms into a new monoclinic crystalline phase under high pressure. This metastable silica polymorph, featuring zigzag chains of SiO6 octahedra, was successfully isolated for the first time.
Area of Science:
- Geochemistry
- Mineral Physics
- Materials Science
Background:
- Alpha-quartz is known to become amorphous under high pressure.
- Understanding silica polymorphs is crucial for geology and materials science.
Purpose of the Study:
- To investigate the high-pressure behavior of alpha-quartz.
- To identify and characterize new crystalline phases of silica under compression.
Main Methods:
- Compression of alpha-quartz to 45 GPa at room temperature using a helium pressure medium.
- X-ray powder diffraction analysis to determine crystal structure.
Main Results:
- Alpha-quartz transformed into a novel monoclinic crystalline phase.
- The structure was indexed to a monoclinic cell with P2(1)/c symmetry.
- The structure consists of 3x2 zigzag chains of SiO6 octahedra.
Conclusions:
- A new, metastable polymorph of silica has been synthesized and characterized.
- This finding contributes to understanding dense silica forms with octahedrally coordinated silicon.