Journal of Physical Chemistry B, Vol.109, No.13, 6193-6203, 2005
Electronic structure of Ag2Cu2O4. Evidence of oxidized silver and copper and internal charge delocalization
The electronic structure of the recently isolated silver copper oxide Ag2Cu2O4 is analyzed along with its precursor Ag2Cu2O3 and similar binary oxides, Ag2O, AgO, CuO, and NaCuO2, using X-ray photoemission (XPS) and X-ray absorption (XAS) measurements. The results for Ag2Cu2O4 reveal an electronic distribution in which silver and copper share a delocalized valence scheme with both metals in formal oxidation states larger than the usual Ag-I and Cu-II. Only one type of crystallographic silver or copper is found, but disorder-strain parameters are considerable and the possibilities of thermal disorder, atomic motion, oxygen contribution, mixed valence, and internal charge delocalization are considered. Classical coordination descriptions for oxidized silver are revisited in terms of this new internal charge delocalization framework found for the electronic structure.