Lattice resonance-induced kinematic nucleation of twins in crystalline materials

Abstract

We present a novel mechanism for twin nucleation in crystalline materials—kinematic twin nucleation—where dislocations spontaneously dissociate into twinning partials due to lattice resonance at specific glide velocities. By modelling dislocation motion using harmonic lattice formalism as moving Kanzaki force distributions in a perfect lattice, we identify resonance velocities where lattice trapping occurs via Van Hove singularities, leading to amplified atomic displacements and the destabilisation of the dislocation core. Molecular dynamics simulations in body-centred cubic (bcc) and hexagonal close-packed (hcp) metals confirm that dislocations moving near these resonance velocities spontaneously dissociate into twinning partials, initiating twin formation without other agency than their own motion, and bypassing energy barriers long since thought to be too high for spontaneous dissociations of dislocations into twinning partials to be possible. Our findings provide a physical rationale for twin structures observed in bcc Fe, and emphasise the crucial role of lattice dynamics in plastic deformation. This universal mechanism expands our understanding of twin nucleation, and opens new avenues for tailoring mechanical properties through controlled manipulation of dislocation velocities.