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Pressure induced self-oxidation of Fe(OH)2
M P Pasternak1, A P Milner, G Kh Rozenberg
1School of Physics and Astronomy, Tel Aviv University, 69978, Tel Aviv, Israel.
Physical Review Letters
|March 5, 2004
Summary
High pressure induces gradual iron oxidation in Fe(OH)2, transforming Fe2+ to Fe3+ without structural changes. This process involves electron ejection and band formation, driven by pressure-deformed dipoles.
Area of Science:
- Geochemistry
- Materials Science
- Solid State Physics
Background:
- Iron hydroxide (Fe(OH)2) is a common mineral phase.
- Understanding its behavior under high pressure is crucial for geochemistry and materials science.
Purpose of the Study:
- To investigate the effects of high pressure on the electronic and structural properties of Fe(OH)2.
- To elucidate the mechanism of iron oxidation under extreme conditions.
Main Methods:
- Mössbauer spectroscopy
- X-ray diffraction
- Electrical resistance measurements up to 40 GPa
Main Results:
- A gradual, non-reversible oxidation of Fe2+ to Fe3+ was observed starting around 8 GPa, reaching 70% Fe3+ abundance at 40 GPa.
- No structural phase transition accompanied the oxidation process.
- Ejected electrons formed a deep band within the high-pressure electronic structure, becoming weakly localized above 50 GPa.
Conclusions:
- Pressure-induced orientationally deformed (OH) dipoles create an effective ionization potential.
- The unusual small binding energy of the valence electron in Fe2+(OH)2 facilitates this high-pressure oxidation process.