Electronic structure of Cu-Au alloys from the Cu perspective: A Cu L(3,2)-edge study

We have obtained Cu L(3,2)-edge x-ray-absorption near-edge structures (XANES) for a series of Cu-Au alloys. It is found that all samples exhibit a three-peal; pattern at the Cu L(3) edge within the first 10(.)eV above the threshold. Close examination reveals chemical systematics in the position of the threshold and of the resonance maxima and in the intensity of the resonances. These results are used to infer charge redistribution at the Cu site. They are compared with previous studies of the same alloys from the Au perspective and with theoretical calculations. Comparisons between the ordered and disordered phase of Cu3Au and CuAu, and the Cu L(3,2-) and K-edge XANES are also made. Our study strongly indicates that d-charge redistribution at the Cu and Au sites is in the opposite direction upon alloy formation; that is, relative to the pure element, Au loses d charge and Cu gains d charge and charge transfer is sensitive to the number of nearest neighbors of unlike atoms.