ATOMIC-PACKING CHARACTERISTICS OF CRYSTALLINE, QUASI-CRYSTALLINE AND AMORPHOUS STRUCTURES OF A SIMPLE METAL SYSTEM

To compare the local atomic-packing geometries among a Frank-Kasper crystalline phase (FK-phase), an icosahedral phase (I-phase) and an amorphous phase (a-phase), model binary MgZn alloys of the three phases have been constructed, and their atomic structures are compared in terms of the Voronoi polyhedra analyses. The results showed that the local atomic-packing of the I-phase resembles closely the FK-phase: the structure consists mostly of tetrahedral units and the majority of atoms form 13-atom icosahedra. The local packing of the a-phase is quite different from the FK- and I-phases: the structure consists of a wide variety of local configurations with a large number of octahedral units and a small fraction of 13-atom icosahedra. The differences in the structural energy among the three phases mainly originate from the difference in the coordination number. © 1990.