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 AuₓCu_1-x and Au0.5Ag0.5 prepared by melt spinning were performed. In the Au0.5Ag0.5 alloy, no significant local deviations of the atoms from the average fcc lattice were detected while in AuₓCu_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 AuₓCu_1-x alloys indicate the weakening of contact between Cu atoms in the dilute limit. Our computer simulation for AuₓCu_1-x clusters of 10⁵ atoms reproduces the main features of both the XAFS and XRD data.