POLYHEDRON AND CAVITY ANALYSES OF A STRUCTURAL MODEL OF AMORPHOUS IRON

Local atomic arrangements were investigated as a model of amorphous iron in terms of Voronoi polyhedra for a dense random packing of hard spheres with and without relaxation. The structure of liquid iron was also simulated in a computer. The amorphous structure was microscopically described as a mosaic of crystalline and noncrystalline polyhedra. The authors have also searched for possible cavities involved in the amorphous structure and found all the Bernal holes. A chain of independent tetragonal dodecahedron (TDs) and trigonal prisms capped with three half-octahedra (TPs), which contact each other on common edges or common faces, could be constructed by trial and error, preferentially retaining the face-contacting holes. If the dislocation model is accepted and the TDs and TPs are regarded as the core structure, the dislocation density is estimated to be 3.4*1014/cm2.