Creation and motion of dislocations and fracture in metal and silicon crystals

摘要

By making a step on one surface (112) of arectangular small parallelepiped copper crystal, dislocationscould be created by the molecular dynamic method. Thedislocation created was not a complete edge dislocation but a pairof Heidenreich-Shockley partial dislocations. Each time adislocation was created, the stress on the surface was released.Small copper crystals having a notch were pulled (until fracture),compressed and buckled by use of the molecular dynamic method.An embedded atom potential was used to represent the interactionbetween atoms. Dislocations were created near the tip of thenotch. A very sharp yield stress was observed.The results of high speed deformations of pure silicon smallcrystals using the molecular dynamics are presented. The resultssuggest that plastic deformation may be possible for the siliconwith a high speed deformation even at room temperature.Another small size single crystal, the same size and the samesurfaces, was compressed using molecular dynamic method. Thesurfaces are {110}, {112} and {111}. The compressed directionwas [111]. It was found that silicon crystals are possible to becompressed with a high speed deformation. This may suggest thatsilicon may be plastically deformed with high speed deformation.