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Title: A new high-pressure phase transition in natural Fe-bearing orthoenstatite

Abstract

Single-crystal X-ray structure refinements have been carried out on natural Fe-bearing orthoenstatite (OEN) at pressures up to 14.53 GPa. We report a new high-pressure phase transition from OEN to a monoclinic phase (HPCEN2) with space group P2{sub 1}/c, with a density change of {approx}1.9(3)%. The HPCEN2 phase is crystallographically different from low-pressure clinoenstatite (LPCEN), which also has P2{sub 1}/c symmetry. Upon release of pressure HPCEN2 reverts to OEN, and the transition pressure is bracketed between 9.96 and 14.26 GPa at room temperature. We find no evidence for a C2/c phase at high pressure. The lattice constants for the new phase at 14.26 GPa are a = 17.87(2), b = 8.526(9), c = 4.9485(10) {angstrom}, {beta} = 92.88(4){sup o} [{rho} = 3.658(9) g/cm{sup 3}]. Refinement of the new structure indicates rotation of tetrahedral chain as the key characteristic of this transition. This experiment points to the possibility of OEN and HPCEN2 as the stable phases in Earth's upper mantle.

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:
1045027
Resource Type:
Journal Article
Resource Relation:
Journal Name: Am. Mineral.; Journal Volume: 97; Journal Issue: (7) ; 07, 2012
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Zhang, Jin S., Dera, Przemyslaw, Bass, Jay D., and UIUC). A new high-pressure phase transition in natural Fe-bearing orthoenstatite. United States: N. p., 2016. Web. doi:10.2138/am.2012.4072.
Zhang, Jin S., Dera, Przemyslaw, Bass, Jay D., & UIUC). A new high-pressure phase transition in natural Fe-bearing orthoenstatite. United States. doi:10.2138/am.2012.4072.
Zhang, Jin S., Dera, Przemyslaw, Bass, Jay D., and UIUC). 2016. "A new high-pressure phase transition in natural Fe-bearing orthoenstatite". United States. doi:10.2138/am.2012.4072.
@article{osti_1045027,
title = {A new high-pressure phase transition in natural Fe-bearing orthoenstatite},
author = {Zhang, Jin S. and Dera, Przemyslaw and Bass, Jay D. and UIUC)},
abstractNote = {Single-crystal X-ray structure refinements have been carried out on natural Fe-bearing orthoenstatite (OEN) at pressures up to 14.53 GPa. We report a new high-pressure phase transition from OEN to a monoclinic phase (HPCEN2) with space group P2{sub 1}/c, with a density change of {approx}1.9(3)%. The HPCEN2 phase is crystallographically different from low-pressure clinoenstatite (LPCEN), which also has P2{sub 1}/c symmetry. Upon release of pressure HPCEN2 reverts to OEN, and the transition pressure is bracketed between 9.96 and 14.26 GPa at room temperature. We find no evidence for a C2/c phase at high pressure. The lattice constants for the new phase at 14.26 GPa are a = 17.87(2), b = 8.526(9), c = 4.9485(10) {angstrom}, {beta} = 92.88(4){sup o} [{rho} = 3.658(9) g/cm{sup 3}]. Refinement of the new structure indicates rotation of tetrahedral chain as the key characteristic of this transition. This experiment points to the possibility of OEN and HPCEN2 as the stable phases in Earth's upper mantle.},
doi = {10.2138/am.2012.4072},
journal = {Am. Mineral.},
number = (7) ; 07, 2012,
volume = 97,
place = {United States},
year = 2016,
month = 7
}