Simulations of dislocation mobility in magnesium from first principles

The strength and ductility of metals are governed by the motion of dislocations, which is quantified by the Peierls stress (σ_p). We use orbital-free density functional theory (OFDFT) to characterize the motion of 13〈112̄0〉 dislocations on the basal {0001} and prismatic {11̄00} planes in hexagonal-close-packed magnesium (Mg) in order to understand its deformation mechanisms. We predict σ_p values of edge dislocations on the basal and prismatic planes to be 0.6 and 35.4 MPa, respectively. The presence of stable stacking faults only on the basal plane produces partial dislocation splitting, which significantly lowers σ_p for basal dislocations. Our atomic scale simulations reveal that dislocation mobility is strongly correlated with the number of core atoms moving collectively. OFDFT σ_p results are in excellent agreement with experiments (∼0.5 and 39.2 MPa), further validating OFDFT as an independent and predictive tool for simulating plastic behavior in main group metals at the mesoscale with first principles' accuracy.