A new model of the medium-range ordered structure in metallic glasses is proposed. The molecular dynamics simulations revealed that there are two different types of basic clusters formed in metallic glasses. One is the icosahedral cluster (I-cluster) formed around the smaller-sized elements, and the other is the Z14, Z15, and Z16 Frank-Kasper clusters (Z-clusters) formed around the bigger-sized elements. The I- and Z-clusters are mainly connected by volume-sharing type connection and form a network extended to the whole glassy phase. Among them, the connection between Z-clusters corresponds to the dicsclination line proposed by Nelson. The topological nature of the network formed by the Z-clusters can be understood by the continuous random network model.
