Thermally-activated non-Schmid glide of screw dislocations in W using atomistically-informed kinetic Monte Carlo simulations

• This paper shows results of kinetic Monte Carlo simulations of thermally activated screw dislocation motion in tungsten.
• Our calculations are important because thermally activated glide cannot be captured using atomistic simulations.
• Our model includes non-Schmid behavior and other features aimed at capturing the full dynamics of dislocation motion.
• We efficiently explore the parametric space of stress, temperature, dislocation length, and loading orientation.
• We condense the results into effective analytical expressions to be used in higher-level methods.

Thermally-activated 1/2〈111〉1/2〈111〉 screw dislocation motion is the controlling plastic mechanism at low temperatures in body-centered cubic (bcc) crystals. Dislocation motion proceeds by nucleation and propagation of atomic-sized kink pairs in close-packed planes. The atomistic character of kink pairs can be studied using techniques such as molecular dynamics (MD). However, MD’s natural inability to properly sample thermally-activated processes as well as to capture {110}{110} screw dislocation glide calls for the development of other methods capable of overcoming these limitations. Here we develop a kinetic Monte Carlo (kMC) approach to study single screw dislocation dynamics from room temperature to 0.5Tm0.5Tm and at stresses 0<σ<0.9σP0<σ<0.9σP, where TmTm and σPσP are the melting point and the Peierls stress. The method is entirely parameterized with atomistic simulations using an embedded atom potential for tungsten. To increase the physical fidelity of our simulations, we calculate the deviations from Schmid’s law prescribed by the interatomic potential used and we study single dislocation kinetics using both projections. We calculate dislocation velocities as a function of stress, temperature, and dislocation line length. We find that considering non-Schmid effects has a strong influence on both the magnitude of the velocities and the trajectories followed by the dislocation. We finish by condensing all the calculated data into effective stress and temperature dependent mobilities to be used in more homogenized numerical methods.