Acta Crystallographica Section A

Foundations of Crystallography

Volume 57, Part 4 (July 2001)

research papers

Acta Cryst. (2001). A57, 406-413 [ doi:10.1107/S0108767301003087 ]

A proposal for a transition mechanism from the diamond to the lonsdaleite type

H. Sowa and E. Koch

Abstract: A phase transition between the diamond ( $Fd\bar3m$ ) and the lonsdaleite types (P6₃/mmc) may be described as a deformation of a homogeneous sphere packing with three contacts per sphere (type 3/10/o1) in the common subgroup Pnna of $Fd\bar3m$ and P6₃/mmc. The frequently observed transition between the zinc-blende ( $F\bar43m$ ) and the wurtzite types (P6₃mc) may be described in an analogous way as a deformation of a heterogeneous sphere packing in the subgroup Pna2₁. The proposed model guarantees the three-dimensional connection during the whole transformation process. By this property it is distinguished from other models.

Keywords: phase transitions; diamond-lonsdaleite; zinc-blende-wurtzite; tridymite-cristobalite; sphere packings.