The efficient cluster packing model – An atomic structural model for metallic glasses

A structural model is described for metallic glasses based on a new sphere packing scheme – the efficient filling of space by solute-centered clusters. This model combines random positioning of solvent atoms with atomic order of solutes. It shows that metallic glasses contain ⩽4 topologically distinct species and that solutes possess specific sizes relative to solvent atoms to produce efficient atomic packing. Validation is achieved by quantitative predictions of nearest-neighbor partial coordination numbers, medium-range solute ordering, density and metallic glass topologies. Good agreement is achieved in each of these areas. This model is able to reproduce compositions for a broad range of metallic glasses, provides specific guidance for the exploration of new bulk metallic glasses and may give new insights into other metallic glass studies. The new scheme introduced here for the efficient filling of space in extended systems of unequal spheres may have relevance to other fields.