Formation and evolution mechanisms of nano-clusters in a large-scale liquid metal system during solidification processes

A molecular dynamics simulation of rapid cooling process has been performed for a large-scale system consisting of 400,000 Al atoms with a supercomputer. To study the formation and evolution mechanisms of nano-clusters in solidification, the so-called cluster-type index method has been applied to describe the structural configurations of the basic small clusters and combined larger clusters obtained from the simulation. The results show that relatively large nano-clusters are formed from small and medium sized clusters through continuous, mutual competitions of annexation and evolution of small clusters in a seesaw manner, giving a structure different from the multi-shell structure where an atom acts as the center of a cluster and the surrounding atoms are arranged according to a certain rule.