Interaction potentials for bulk metallic glasses that can generate both brittle and ductile mechanical response*

Bulk metallic glasses (BMGs) have desirable mechanical properties such as high yield strength and elasticity compared to conventional alloys. However, BMGs are typically brittle, which limits their viability for structural applications. We perform molecular dynamics simulations to understand the ductility of model glass formers that interact via the Lennard-Jones, Stillinger-Weber, and embedded atom method potentials. We prepare binary BMGs over a range of cooling rates and perform athermal quasi-static uniaxial tension tests. We correlate the ductility with the fictive temperature, depth in the potential energy landscape, and measures of local structural order. We show that we can prepare samples that span a wide range of mechanical responses for all of the interaction potentials that we study. We also present a phenomenological spring network model that describes brittle and ductile response in terms of the number of springs that have broken and reformed in response to applied strain. We identify the parameters in the model that control the behavior of the stress versus strain curve, which allows us to achieve quantitative agreement with the results from the simulation of uniaxial tension.