Nucleation of a (1¯012) twin in hexagonal close-packed crystals

We have studied the atomic structures of the nucleus of a [101¯1](1¯012) twin in Mg by atomistic simulations using density function theory and an empirical potential. The twinning mechanism for (1¯012) twins is described. The results show that the nucleus consists of one partial dislocation with a Burgers vector of -50/107[101¯1] together with multiple twinning dislocations (TDs) with a Burgers vector of 1/15[101¯1]. The minimum, stable nucleus involves eight TDs and one partial dislocation, corresponding to a thickness of 17 crystallographic planes.