A transition path for the pressure-induced wurtzite-to NaCl-type transformation described in Pna2

Quite recently, two further mechanisms for the pressure-induced transition from the wurtzite to the NaCl type were proposed [Shimojo et al. ( 2004). Phys. Rev. B, 70, 184111-1-6] but no symmetry information was given. It will be shown that a slight modification of one of the assumed transition pathways allows a crystallographic description on the basis of a deformation of a heterogeneous 4-connected sphere packing in Pna2(1). All investigations were done with the help of the corresponding homogeneous packing in Pnma where the transition may be described as a deformation of a lonsdaleite configuration into a cubic primitive lattice cP. During the transformation, all sphere contacts are maintained. The new transition model is compared with the well known Cmc2(1) mechanism. Further related mechanisms can also be derived.