Simulation study of the evolution mechanisms of clusters in a large-scale liquid Alsystem during rapid cooling processes

Abstract

Molecular dynamics simulations have been performed for a large-scale systemconsisting of 400 000 atoms of liquid metal Al. To describe the complexmicrostructural evolutions in the liquid system during the rapid cooling processes,the tracing atom method and cluster bond-type index method have been used. Itis demonstrated that the number of (12 0 12 0) icosahedral clusters, consisting ofthe 1551 bond type, with a higher degree of ordering, increases continuously andplays a critical and leading role in the solidifying transition. Various clusterconfigurations, formed by icosahedral clusters and Frank–Kasper, Bernaland defective polyhedra, produce the short-range-order regions in thisamorphous system, while the atoms not taking part in forming clustersgive the sparse regions possessing disorder characteristics. Large clusterconfigurations consisting of more than 150 atoms have been found and areshown to be formed by combining smaller clusters and to be differentfrom those obtained by gaseous deposition and ionic spray methods.