Competing intermediates in the pressure-induced wurtzite to rocksalt phase transition in ZnO

Molecular-dynamics simulations are carried out on the wurtzitelike (B4) to rocksaltlike structure (B1) pressure-induced phase transition in ZnO. A tetragonal intermediate (iT) appears at the B4/B1 interface along the transition. A hexagonal intermediate (iH) of h-BN type is also occasionally visited, as a result of axial compression, which however does not represent a necessary step for the transition. The presence of small fractions of rocksalt or defects after B1 -> B4 back transformation is traced back to the competition between deformation modes connected to iT or iH.