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Molecular dynamics simulation on microstructure evolution during solidification of copper nanoparticles

The effect of cooling rate on the microstructure evolution of liquid Cu nanoparticles during their solidification process is investigated by using a molecular dynamics simulation based on the embedded atom method (EAM) potential developed by Foiles et al.. The potential energy analysis, the pair distribution function and the common neighbor analysis have been used. The results show that the solidification point increases with decreasing cooling rate and that the solidification of the microstructure of Cu nanoparticles varies with the cooling rate. The microstructure consists of fcc, hcp and bcc crystals or mixtures, though the fcc structure dominates, except in the amorphous state. An amorphous structure was obtained when the cooling rate reached 1.0 × 1013 K/s or higher while crystallization degree increased with decreasing cooling rate, and the total content of crystal structures reached to 95% when the cooling rate dropped to 4.0 × 1011 K/s, which was nearly a perfect crystal structure. The results also indicate that a single-crystal nanoparticle will not be obtained by quenching the liquid metal under various cooling rates.