Coupling Quantum and Continuum Scales to Predict Dislocation Nucleation from an Aluminum Crack Tip in the Presence of Oxygen and Hydrogen

Abstract

Atomistic simulations of deformation processes have long been plagued by the challenge of accurately and efficiently describing the complexities of multispecies bonding. In the case of metals, this has led to the majority of atomistic modeling efforts focusing on pure elemental metals in vacuum, rather than more technologically relevant problems involving alloys with impurities and surface oxides in realistic environments. At the root of the challenge is a trade-off between accuracy and computational expense. Here we use a concurrent multi-scale approach to address this long-standing challenge in the context of crack tip behavior in Al. We couple an atomistic region whose forces are calculated via Kohn-Sham Density Functional theory to a continuum region described by linear elasticity. This approach enables us to accurately capture complex chemistry at the crack tip while properly accounting for long-range elastic fields via a large simulation domain. The method is used to predict the critical stress intensity factor for both crack tip dislocation nucleation and propagation in the presence of oxygen and hydrogen. Interpreting the mechanical results alongside of charge analysis reveals new insight into the role of chemistry at a crack tip.