Pressure-induced structural modulations in coesite
Publication Date
2018-09-20Journal Title
Physical Review B - Condensed Matter and Materials Physics
ISSN
1098-0121
Publisher
American Physical Society
Volume
98
Number
104106
Type
Article
Metadata
Show full item recordCitation
Wu, Y., Liu, H., Haijun, H., Fei, Y., Feng, X., & Redfern, S. (2018). Pressure-induced structural modulations in coesite. Physical Review B - Condensed Matter and Materials Physics, 98 (104106) https://doi.org/10.1103/PhysRevB.98.104106
Abstract
Silica phases, SiO2, have attracted significant attention as important phases in the fields of condensed matter physics, materials science, and (in view of their abundance in Earth’s crust) geoscience. Here, we experimentally and theoretically demonstrate that coesite undergoes structural modulations under high pressure. Coesite transforms to a distorted modulated structure, coesite-II, at 22-25 GPa with modulation wave vector q = 0.5b*. Coesite-II displays further commensurate modulation along the y-axis at 36-40 GPa and the long-range ordered crystalline structure collapses beyond ~40 GPa and starts amorphizing. First-principles calculations illuminate the nature of the modulated phase transitions of coesite and elucidate the modulated structures of coesite caused by modulations along y-axis direction. The structural modulations are demonstrated to result from phonon instability, preceding pressured-induced amorphization. The recovered sample after decompression develops a rim of crystalline coesite structure, but its interior remains low crystalline or partially amorphous. Our results not only clarify that the pressure-induced reversible phase transitions and amorphization in coesite originate from structural modulations along y-axis direction, but also shed light on the densification mechanism of silica under high pressure.
Sponsorship
NERC grant NE/P012167/1
Funder references
Natural Environment Research Council (NE/P012167/1)
Identifiers
External DOI: https://doi.org/10.1103/PhysRevB.98.104106
This record's URL: https://www.repository.cam.ac.uk/handle/1810/285047
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