Abstract
Morphology and mechanical properties of atomic-cluster-assembled structures, which are generated from nano-size cluster of metallic atoms, are studied by using molecular dynamics with many-body interatomic potential. Generation of the structures is carried out by configuring copper clusters (made up of 683 atoms) in regular array with initial approaching velocities. It is confirmed that one-dimensional, two-dimensional, and three-dimensional structures can be designed and fabricated from clusters. Shape of the structures is largely dependent on initial velocities, that is, initial kinetic energy attributed to clusters. In two-dimensional model with low approaching velocity, some structures have voids and show large surface ratio. Subsequently, tensile test is conducted on the structures. By chucking two end regions and pulling them in opposite direction, tensile straining of the structures is carried out. Strain energy calculated from stress-strain curve over testing process can be used as an effective evaluation value for distinguishing ductile structures from brittle structures. On the other hand, tensile strength (maximum stress) does not have marked variation as to the shape of structures. It is found that, in two-dimensional structures, existence of voids enhances the brittleness. It is because, when the structure has void inside, stacking faults appear and disappear more easily than when the structure gets rid of void by clusters being packed closely. Strain rate, as another factor which may alter the mechanical properties, is diminished from that of principal result to smaller value, corresponding to tensile velocity from 100m/s to 5m/s. Though the tensile strength and strain energy are influenced slightly by strain rate, they are always low for the structure with voids.
