624 金属ナノクラスターのモルフォロジーと堆積過程の分子動力学解析

概要

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The initial period of the deposition process of a metallic cluster in the soft-landing regime is investigated by the molecular-dynamics simulation. The embedded-atom method potential is adopted for calculation of the interaction between metallic atoms. In the simulation of free clusters, it is found a cluster consisting of 249 Au atoms has a multiply-twinned structure similar to that identified by the TEM observation in the literature. In the deposition simulation, the calculation begins with preliminary equilibration of a cluster and a substrate at a specified temperature. The lowest atomic layer in the substrate is fixed, and the next two layers are set to be velocity-scaling layers during the deposition process. the periodic boundary conditions are imposed in the horizontal directions. A single cluster with no velocity is deposited on the substrate. The simulation is performed at different temperatures of the cluster and substrate and for different sizes of the cluster. The simulation reveals that for some cases, the potential energy of the system decreases monotonically after a cluster has been deposited while for other cases, it has a transient minimum. The existence of this transient minimum can be understood by considering the increase of the surface energy during the morphological change of a cluster by which it crystallographically accommodates itself to the substrate.
社団法人日本機械学会の論文
2003-09-23