Pressure induced self-oxidation of Fe(OH)2.

Mössbauer spectroscopy, x-ray diffraction, and electrical resistance [R(P,T)] studies in Fe(OH)(2) to 40 GPa revealed an unforeseen process by which a gradual Fe2+ oxidation takes place, starting at approximately 8 GPa reaching 70% Fe3+ abundance at 40 GPa. The nonreversible process Fe2+-->Fe3++e(-) occurs with no structural transition. The "ejected" electrons form a deep band within the high-pressure electronic manifold becoming weakly localized at P>50 GPa. This process is attributed to an effective ionization potential created by the pressure induced orientationally deformed (OH) dipoles and the unusual small binding energy of the valence electron in Fe2+(OH)(2).