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

Abstract

Neutron diffraction was used to investigate the structure of the liquid alloys Au${}_{0.81}$Si${}_{0.19}$, Au${}_{0.72}$Ge${}_{0.28}$, and Ag${}_{0.74}$Ge${}_{0.26}$ 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 \AA{} to beyond 20 \AA{}, 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.