A Structural Model of Transition of Cubic α-Mn Into a Hexagonal Modification Based on Noncrystallographic Symmetry of Clusters

A structural model of the transformation of cubic α-Mn into high-pressure hexagonal close-packed ε -Mn phase is suggested. The model is based on the transformation of a triple of tetrahedrons into an octahedron, implemented through a shift of the diagonal of a nonplanar “rhombus” formed by the faces of neighboring tetrahedrons. Asystem of such transformations transfers a fragment of a tetrahedral α -Mn spiral into a fragment of a rod composed of octahedrons in hexagonal closest packing. The model takes into account the noncrystallographic symmetry of the considered fragments of the crystalline phases.