During the course of exploration in the Mg-Pd-Zn system, a new 1/1 body-centered-cubic quasicrystal (QC) approximant phase, adopting a new structure type (cI146), has been discovered. According to single crystal x-ray diffraction studies, the composition of the new phase is Mg11.71Pd0.07Zn4.92. The new approximant phase shows a close structural relationship with the parent orthorhombic Mg50Zn20 structure, and exhibits a shell structure based on (1) an inner icosahedron, (2) a truncated icosahedron, (3) a larger icosahedron, and (4) a 72-vertex polyhedron.
A part of this structure mimics a filled variant of Mackay-type clusters, but this discovery represents a new cubic approximant structure for QCs. Only a small amount of Pd is needed for the structure to crystallize in cubic symmetry. The valence electron concentration of this new QC approximant is ca. 2.0 electrons/atom.