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Title: New insights into the high-pressure polymorphism of SiO[subscript 2] cristobalite

Abstract

Single-crystal X-ray diffraction experiments with SiO{sub 2} {alpha}-cristobalite reveal that the well-known reversible displacive phase transition to cristobalite-II, which occurs at approximately 1.8 GPa, can be suppressed by rapid pressure increase, leading to an overpressurized metastable state, persisting to pressure as high as 10 GPa. In another, slow pressure increase experiment, the monoclinic high-pressure phase-II was observed to form at {approx}1.8 GPa, in agreement with earlier in situ studies, and its crystal structure has been unambiguously determined. Single-crystal data have been used to refine the structure models of both phases over the range of pressure up to the threshold of formation of cristobalite X-I at {approx}12 GPa, providing important constraints on the feasibility of the two competing silica densification models proposed in the literature, based on quantum mechanical calculations. Preliminary diffraction data obtained for cristobalite X-I reveal a monoclinic unit cell that contradicts the currently assumed model.

Authors:
; ; ; ;  [1];  [2]
  1. (UC)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCESNSF
OSTI Identifier:
1022271
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Chem. Miner.; Journal Volume: 38; Journal Issue: (7) ; 04, 2011
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Dera, Przemyslaw, Lazarz, John D., Prakapenka, Vitali B., Barkley, Madison, Downs, Robert T., and Ariz). New insights into the high-pressure polymorphism of SiO[subscript 2] cristobalite. United States: N. p., 2016. Web. doi:10.1007/s00269-011-0424-5.
Dera, Przemyslaw, Lazarz, John D., Prakapenka, Vitali B., Barkley, Madison, Downs, Robert T., & Ariz). New insights into the high-pressure polymorphism of SiO[subscript 2] cristobalite. United States. doi:10.1007/s00269-011-0424-5.
Dera, Przemyslaw, Lazarz, John D., Prakapenka, Vitali B., Barkley, Madison, Downs, Robert T., and Ariz). Fri . "New insights into the high-pressure polymorphism of SiO[subscript 2] cristobalite". United States. doi:10.1007/s00269-011-0424-5.
@article{osti_1022271,
title = {New insights into the high-pressure polymorphism of SiO[subscript 2] cristobalite},
author = {Dera, Przemyslaw and Lazarz, John D. and Prakapenka, Vitali B. and Barkley, Madison and Downs, Robert T. and Ariz)},
abstractNote = {Single-crystal X-ray diffraction experiments with SiO{sub 2} {alpha}-cristobalite reveal that the well-known reversible displacive phase transition to cristobalite-II, which occurs at approximately 1.8 GPa, can be suppressed by rapid pressure increase, leading to an overpressurized metastable state, persisting to pressure as high as 10 GPa. In another, slow pressure increase experiment, the monoclinic high-pressure phase-II was observed to form at {approx}1.8 GPa, in agreement with earlier in situ studies, and its crystal structure has been unambiguously determined. Single-crystal data have been used to refine the structure models of both phases over the range of pressure up to the threshold of formation of cristobalite X-I at {approx}12 GPa, providing important constraints on the feasibility of the two competing silica densification models proposed in the literature, based on quantum mechanical calculations. Preliminary diffraction data obtained for cristobalite X-I reveal a monoclinic unit cell that contradicts the currently assumed model.},
doi = {10.1007/s00269-011-0424-5},
journal = {Phys. Chem. Miner.},
number = (7) ; 04, 2011,
volume = 38,
place = {United States},
year = {Fri Jul 29 00:00:00 EDT 2016},
month = {Fri Jul 29 00:00:00 EDT 2016}
}