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Title: Pressure-induced phase transitions in coesite

Authors:
; ; ; ; ; ; ;  [1];  [2];  [2];  [2]
  1. (CNRS-UMR)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
FOREIGN
OSTI Identifier:
1150121
Resource Type:
Journal Article
Resource Relation:
Journal Name: Am. Mineral.; Journal Volume: 99; Journal Issue: (4) ; 2014
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Cernok, Ana, Ballaran, Tiziana Boffa, Caracas, Razvan, Miyajima, Nobuyoshi, Bykova, Elena, Prakapenka, Vitali, Liermann, Hanns-Peter, Dubrovinsky, Leonid, DESY), Bayreuth), and UC). Pressure-induced phase transitions in coesite. United States: N. p., 2014. Web. doi:10.2138/am.2014.4585.
Cernok, Ana, Ballaran, Tiziana Boffa, Caracas, Razvan, Miyajima, Nobuyoshi, Bykova, Elena, Prakapenka, Vitali, Liermann, Hanns-Peter, Dubrovinsky, Leonid, DESY), Bayreuth), & UC). Pressure-induced phase transitions in coesite. United States. doi:10.2138/am.2014.4585.
Cernok, Ana, Ballaran, Tiziana Boffa, Caracas, Razvan, Miyajima, Nobuyoshi, Bykova, Elena, Prakapenka, Vitali, Liermann, Hanns-Peter, Dubrovinsky, Leonid, DESY), Bayreuth), and UC). Tue . "Pressure-induced phase transitions in coesite". United States. doi:10.2138/am.2014.4585.
@article{osti_1150121,
title = {Pressure-induced phase transitions in coesite},
author = {Cernok, Ana and Ballaran, Tiziana Boffa and Caracas, Razvan and Miyajima, Nobuyoshi and Bykova, Elena and Prakapenka, Vitali and Liermann, Hanns-Peter and Dubrovinsky, Leonid and DESY) and Bayreuth) and UC)},
abstractNote = {},
doi = {10.2138/am.2014.4585},
journal = {Am. Mineral.},
number = (4) ; 2014,
volume = 99,
place = {United States},
year = {Tue Aug 19 00:00:00 EDT 2014},
month = {Tue Aug 19 00:00:00 EDT 2014}
}
  • Quartz and closely related materials will transform under pressure from crystalline states to amorphous forms. Here we examine coesite, a high-pressure form of silica which also undergoes pressure induced amorphization. We find that coesite, like quartz, possesses a shear instability closely coupled to a zone-edge phonon softening at pressures comparable to the amorphization transformation. The commonality of these features strongly suggests that a coupling between a shear and a phonon soft mode plays an important role in pressure induced amorphization. This mechanism is similar to that observed in martensitic transformations. The densities for the phases produced at high pressures, asmore » calculated from variable cell shape molecular dynamics, follow the experimental glassy region joining coesite to stishovite. (c) 2000 The American Physical Society.« less
  • High-pressure Raman scattering and optical absorption studies have been carried out on lead pyroniobate (Pb{sub 2}Nb{sub 2}O{sub 7}) up to 33 GPa, using a gasketed diamond anvil cell. The Raman study reveals the occurrence of two, possibly three, pressure-induced phase changes; a rather subtle change is indicated near 4.5 GPa. The transition near 13 GPa is attributed to a structural transition from the rhombohedral to the cubic pyrochlore structure. The third phase change occurs near 20 GPa. From the broad Raman feature that is observed at about 800 cm{sup {minus}1}, it is concluded that the system turns amorphous at pressuresmore » above 20 GPa. The amorphous phase recrystallizes to the original rhombohedral phase, on release of pressure. The broad Raman peaks of the recrystallized phase indicate a high degree of disorder in the material. Lead pyroniobate turns deep red near 30 GPa, from light yellow at ambient pressure. Semi quantitative absorption measurements show that the energy gap shifts red at a rate of 30 meV/GPa. This shift is attributed to the downward motion of the 5d (es) conduction band of Pb.« less