Structural evolution in Au- and Pd-based metallic glass forming liquids and the case for improved molecular dynamics force fields

Abstract

The results of a combined experimental and computational investigation of the structural evolution of Au81Si19, Pd82Si18, and Pd77Cu6Si17 metallic glass forming liquids are presented. Electrostatically levitated metallic liquids are prepared, and synchrotron x-ray scattering studies are combined with embedded atom method molecular dynamics simulations to probe the distribution of relevant structural units. Metal–metalloid based metallic glass forming systems are an extremely important class of materials with varied glass forming ability and mechanical processibility. High quality experimental x-ray scattering data are in poor agreement with the data from the molecular dynamics simulations, demonstrating the need for improved interatomic potentials. The first peak in the x-ray static structure factor in Pd77Cu6Si17 displays evidence for a Curie–Weiss type behavior but also a peak in the effective Curie temperature. A proposed order parameter distinguishing glass forming ability, [Formula: see text], shows a peak in the effective Curie temperature near a crossover temperature established by the behavior of the viscosity, T A.