BSTRACTDeformation twins grow by the motion of disconnections along their interfaces

thereby coupling shear with migration. Atomic-scal

e simulations of this mechanism have advanced to the point where the trajectory of each atom can be followed as it transits from a site in the shrinking grain

through the interface

and onwards to a site in the growing twin. Historically

such trajectories have been factorised into shear and shuffle components according to some defined convention. In the present article

we introduce a method of factorisation consistent with disconnection motion. This procedure is illustrated for the case of twinning in hexagonal close-packed materials

and shown to agree with simulated atomic trajectories for Zr.

IMPACT STATEMENT

Shear and shuffle displacements accompanying () twinning are quantified consistently with growth by the observed mechanism of disconnection motion. This advance will facilitate the understanding of twinning kinetics.