Molecular dynamics investigations of structural changes accompanying with freezing a molten Cu-135 cluster on cooling

摘要

We use molecular dynamics (MD) simulations within the framework of the embedded-atom method (EAM) to investigate structural changes during freezing a molten Cu cluster containing 135 atoms. The simulations show how the structural changes can strongly cause internal energy to change accordingly, and reveal that continuous interchange positions of atoms are the key in the formation of the icosahedral (Ih)-like Cu-135 cluster. By using visual inspection on atomic packing according to atomic density profiles, we analyze crystallization processes during freezing the molten cluster. At the initial stage of the freezing, one atom moves into the center of this cluster. Then the packing in interior atoms is changed into an ordered Ih structure, while outer atoms are becoming locally ordered with a fivefold Ih symmetry. Subsequently, nanocrystallization at lower temperatures propagates outward from the interior Ih structure, leading to the Ih-like cluster.