Local structure of disordered Au-Cu and Au-Ag alloys

X-ray-absorption fine structure (XAFS) and x-ray-diffraction (XRD) measurements of disordered alloys Au_xCu_1-x and Au_0.5Ag_0.5 prepared by melt spinning were performed. In the Au_0.5Ag_0.5 alloy, no significant local deviations of the atoms from the average fcc lattice were detected while in Au_xCu_1-x alloys, significant deviations of atoms from the average fcc lattice were found. Mean-square vibrations of the Cu-Cu distances revealed by the XAFS in Au_xCu_1-x alloys indicate the weakening of contact between Cu atoms in the dilute limit. Our computer simulation for Au_xCu_1-x clusters of 10⁵ atoms reproduces the main features of both the XAFS and XRD data.