Evolution Mechanisms of Nano-Clusters in a Large-Scale System of 10⁶ Liquid Metal Atoms During Rapid Cooling Processes

Abstract

A molecular dynamics simulation study has been performed for a large-sized system consisting of 106 liquid metal Al atoms to investigate the evolution characteristics of nano-clusters formed during rapid solidification processes. The cluster-type index method (CTIM) has been applied to describe the structural configurations of the basic clusters and nano-clusters. The results show that the icosahedral clusters (12 0 12 0) and their combinations play a critical role in the microstructural transitions. The nano-clusters are mainly formed by combining basic and medium sized clusters through continuous evolution. Their structural configurations are different from the multi-shell structures obtained by gaseous deposition, ionic spray, and so on. The central atoms of basic clusters composing the nano-cluster are bonded with each other, some central atoms are multi-bonded, and others single-bonded.

Formation and Evolution Characteristics of Nano-Clusters (For Large-Scale Systems of 106 Liquid Metal Atoms)

“…The theoretical works were mainly carried out on diversified individual clusters configured by accumulating atoms according to some fixed pattern (Liu C. S. et al, 2001;Solov'yov et al, 2003;Doye & Meyer, 2005;Li H. & Pederiva, 2003;Ikeshoji et al, 1996;Wang L et al, 2002;Haberland et al, 2005;Joshi et al, 2006;Noya et al, 2007;Cabarcos et al, 1999;Orlando & James, 1999;Alfe, 2003). However, it is interesting that the similar clusters or aggregations have been found in some liquid metals during rapid solidification processes in our MD simulations ( Liu R. S. et al, 1992a( Liu R. S. et al, , 1992b( Liu R. S. et al, , 1995( Liu R. S. et al, , 2005a( Liu R. S. et al, , 2005b( Liu R. S. et al, , 2007a( Liu R. S. et al, , 2007b( Liu R. S. et al, , 2007cDong K. J. et al, 2003;Liu F. X. et al, 2009;Hou Z. Y. et al, 2009Hou Z. Y. et al, , 2010aHou Z. Y. et al, , 2010b and that it is also important for understanding in depth the solidification processes from liquid state to solid state. Furthermore, the formation and evolution characteristics of cluster configurations, especially the nano-cluster configurations, formed during solidification processes of liquid metals are still not well known up to now.…”

“…In this chapter, the main purpose is to further extended our previous MD simulation method (Liu R. S. et al, 2007a(Liu R. S. et al, , 2007b(Liu R. S. et al, , 2007cTian et al, 2008Tian et al, , 2009Zhou et al, 2011) to study the large-sized systems consisting of 10 6 atoms of liquid metal Al and Na. Using the center-atom method, bond-type index method, and cluster-type index method (we proposed), the results have been analyzed and demonstrated that the larger simulation system can lead to a better understanding of the formation and evolution characteristics of the cluster configurations, especially the nano-clusters during solidification processes.…”