Simulations of dislocation mobility in magnesium from first principles

• We investigate dislocation mobility in HCP Mg using the linear scaling OFDFT method.
• Mg Peierls stresses are extracted for the first time from quantum simulations.
• OFDFT Peierls stresses are in excellent agreement with experiments.
• Anisotropic plasticity between prismatic vs. basal slip is well-reproduced.
• This anisotropy is strongly correlated with the number of atoms moving collectively.

The strength and ductility of metals are governed by the motion of dislocations, which is quantified by the Peierls stress (σp  ). We use orbital-free density functional theory (OFDFT) to characterize the motion of 13〈112¯0〉 dislocations on the basal {0001} and prismatic {11¯00} planes in hexagonal-close-packed magnesium (Mg) in order to understand its deformation mechanisms. We predict σp 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 σp for basal dislocations. Our atomic scale simulations reveal that dislocation mobility is strongly correlated with the number of core atoms moving collectively. OFDFT σp 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.