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High-pressure behavior of the polymorphs of FeOOH

Mary M. Reagan, Arianna E. Gleason, Luke Daemen, Yuming Xiao and Wendy L. Mao
High-pressure behavior of the polymorphs of FeOOH
American Mineralogist (June 2016) 101 (6): 1483-1488


The high-pressure structural and electronic behavior of alpha -, beta -, and gamma -FeOOH were studied in situ using a combination of synchrotron X-ray diffraction (XRD) and X-ray emission spectroscopy (XES). We monitored alpha -FeOOH by XES as a function of pressure up to 85 GPa and observed an electronic spin transition that began at approximately 50 GPa, which is consistent with previous results. In the gamma -FeOOH sample, we see the initiation of a spin transition at 35 GPa that remains incomplete up to 65 GPa. beta -FeOOH does not show any indication of a spin transition up to 65 GPa. Analysis of the high-pressure XRD data shows that neither beta -FeOOH nor gamma -FeOOH transform to new crystal structures, and both amorphize above 20 GPa. Comparing our EOS results for the beta and gamma phases with recently published data on the alpha and epsilon phases, we found that beta -FeOOH exhibits distinct behavior from the other three polymorphs, as it is significantly less compressible and does not undergo a spin transition. A systematic examination of these iron hydroxide polymorphs as a function of pressure can provide insight into the relationship between electronic spin transitions and structural transitions in these OH- and Fe (super 3+) -bearing phases that may have implications on our understanding of the water content and oxidation state of the mantle.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 101
Serial Issue: 6
Title: High-pressure behavior of the polymorphs of FeOOH
Affiliation: Stanford University, Department of Geological Sciences, Stanford, CA, United States
Pages: 1483-1488
Published: 201606
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 31
Accession Number: 2016-079209
Categories: Geophysics of minerals and rocks
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Secondary Affiliation: Los Alamos National Laboratory, USA, United StatesOak Ridge National Laboratory, USA, United StatesArgonne National Laboratory, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201638
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