Fe In Oxidation States Research Articles

Stability of Hydroxylated α-Fe2O3(0001) Surfaces.

The stability of hydroxylated terminations of the 0001 surface of α-Fe2O3 (hematite) is investigated computationally using PBE + U calculations with dispersion corrections. Hydroxylated surfaces with low OH concentrations are found to be most stable in a range of the chemical potential of water of -0.95 eV > μH2O > -2.22 eV. These surfaces can be described as isolated Fe(OH)3 groups adsorbed on the dry hematite surface and are predicted to be the exposed termination of the 0001 surface in a wide range of relevant experimental conditions. Most investigated reduced surfaces, containing Fe in oxidation state +2, are only stable in a range of the chemical potential of oxygen μO < -2.44 eV, where bulk hematite is less than magnetite. The only reduced surface stable at a higher μO is derived from the most stable nonreduced hydroxylated surfaces by removing a single OH group per unit cell.

XPS study of the electron structure of heterometallic trinuclear complexes Fe2M(μ3-O)(μ-Piv)6(HPiv)3 (M[dbnd]Mn, Co, Ni)

Electron structure of pivalate heterometallic trinuclear complexes with a triangular structure and varying ligands environment is studied by the XPS method. An effect of substitution of one of the Fe atoms by MMn, Co, Ni on Fe2p and M2p spectra is studied. Redistribution of electron density in an OCO group upon formation of complexes and introduction of donor ligands is discovered. Correlation of the characteristics of photoelectron spectra with the variation of ligands environment is studied. The complexes are assigned to high-spin ones with Fe in oxidation state III, and M, II. A relation is established between Fe2p-spectra characteristics and electron affinity of M ions.