  Twin growth in hexagonal close-packed zirconium is investigated at the atomic
scale by modeling the various disconnections that can exist on twin boundaries.
Thanks to a coupling with elasticity theory, core energies are extracted from
atomistic simulations and the formation energy of isolated disconnection
dipoles is defined. For twin systems where several disconnections can exist,
because of this core contribution, the most stable disconnection is not always
the one with the smallest Burgers vector. Crystallographic parameters of the
disconnection with the lowest formation energy correlate well with twin modes
observed experimentally. On the other hand, disconnection migration,
characterized here by computing their migration energy and Peierls stress, does
not appear critical for twin mode selection.
