Molecular dynamics analysis of metal nano-cluster in coalescence process
Saitoh Ken-ichi
Abstract:Coalescence process of copper nano-clusters is investigated by molecular dynamics simulation using inter-atomic interaction based on effective-medium theory. Stable atomic configuration at 0 K is determined for several spherical clusters and icosahedral structure composed of 13, 55, or 147 atoms is obtained. Excess energy of clusters averaged over approximated surface area is larger than that of a flat surface. Compressive stress and high atomic energy exist near center in small clusters. By interaction simulation between two equivalent clusters, in which they approach each other with some offset distance or some initial rotation motion and coalesce, it is found that rotation motion of the whole body is generated as a consequence and that rotational kinetic energy obtained after coalescence is affected by size of the original cluster and initial offset distance. Transition from translational kinetic energy to rotational kinetic energy completes in less than 1 picosecond. In clusters system composed of 1366 atoms, it is shown, by the analysis of coordination number or atomic configurations and trajectories, that compressive deformation in coalescence process becomes smaller with increasing initial offset distance. In the system with small number of atoms, lattice vibration is large and it is supposed that rearrangement of atomic structure is relatively easy. Key Words:Molecular dynamics, Nano-cluster, Effective-medium theory, Copper, Syrface, Rotational kinetic energy, Coalescence, Nucleation, Collision, Coordination