A molecular dynamics simulation study has been performed for a large-sized system consisting of 106 liquid metal Al atoms to investigate the formation and magic number characteristics of various clusters formed during solidification processes. The cluster-type index method (CTIM) is adopted to describe various types of cluster by basic clusters. It is demonstrated that the icosahedral cluster (12 0 12 0) is the most important basic cluster, and that it plays a critical role in the microstructure transition. A new statistical method has been proposed to classify the clusters as some group levels according to the numbers of basic clusters contained in each cluster. The magic numbers can be determined by the respective peak value positions of different group levels of clusters, and the magic number sequence in the system is 13, 19, 25(27), 31(33), 38(40), 42(45), 48(51), 55(59), 61(65), 67,... the numbers in the brackets are the second magic number of the corresponding group levels of clusters. This magic number sequence is in good agreement with the experimental results obtained by Schriver and Harris et al, and the experimental results can be reasonably well explained.

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.

A molecular dynamic simulation study has been performed for a large-sized system consisting of 106 liquid metal Al atoms to deeply investigate the formation and magic number characteristics of various cluster formed during solidification processes. It has been found that the numbers of various types of cluster in the system obviously possess peak values, namely, magic numbers. The first, second, third, .…,and tenth magic numbers are determined in turn in the order of 13, 19, 25(27), 31(33), 38(40), 42(45), 48(51), 55(59), 61(65), 67,…( the numbers in the brackets are the second peak values in the corresponding level of cluster). This magic number serial is in good agreement with the experimental results obtained by Harris et al, and this method determining the magic numbers from the clusters according to the level of basic cluster can be used to afford a primary scientific and reasonable explanation to experimental results.

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The molecular dynamics simulation studies on the microstructure evolution properties of amorphous Ca7Mg3 alloy during the isothermal annealing have been performed. The simulated structure factor S(q) of Ca7Mg3 is well agreed with the experimental data. Results indicate that the metallic glass of Ca7Mg3 alloy is relaxed into amorphous structure of greater stability in which much more icosahedron structures is formed; interestingly, it is also found that the short short-range order has no change, while the short-range order of the system increases during the isothermal annealing process.