Electronegativity versus Fermi energy in oxides: the role of formal oxidation state

A new method derived from the Nethercot postulate is used to evaluate the Fermi energy (E-f) of simple iono-covalent oxides. One demonstrates that Ef is only determined from the electronegativity of the cations (X) and of its formal oxidation state (z) leading to the formula: E-f = (-0.12z + 1.26)x + 1.13z - 0.17 A mathematical consequence of this expression is that when the electronegativity of cations increases, the Fermi energies of the corresponding oxides tend towards an isoelectronegativity point whatever may be the oxidation number. In practice, it is applicable to the most covalent oxides such as P2O5, SeO3, XeO3, Re2O7, OsO4 and others. (C) 2003 Elsevier B.V. All rights reserved.