Structure of eutectic liquids in the Au-Si, Au-Ge, and Ag-Ge binary systems by neutron diffraction

Neutron diffraction was used to investigate the structure of the liquid alloys Au_0.81Si_0.19, Au_0.72Ge_0.28, and Ag_0.74Ge_0.26 with composition at or near the eutectic. For a given alloy, the measured pair distribution function is described over a wide range of distances, from 5–6 Å to beyond 20 Å, by an exponentially damped oscillatory function with a decay length and wavelength of oscillation related to the half-width at half-maximum of the principal peak in the total structure factor and to the position of this peak, respectively. This behavior is expected from solutions of the Ornstein-Zernike equations for simple pair potentials. There is no need to invoke the existence of a fractal network, as suggested by a recent analysis of the diffraction patterns measured for amorphous metallic alloys, to account for the experimental results. A reconsideration of the diffraction data for these amorphous alloys points to the same conclusion.