Molecular Dynamics Study of the Mechanical Properties of Nickel Nanoparticles with a Nanocrystalline Structure

Using the molecular dynamics method, the compression of nickel nanoparticles with a nanocrystalline structure at low temperatures was simulated. The influence of the nanoparticle size (from 2 to 20 nm) and the average grain size within it (from 2 to 8 nm) on the compressive strength and on the strain at which the maximum stress is reached was investigated. In addition, the stability of the nanocrystalline structure of the nanoparticles was studied as a function of temperature and grain size. It is shown that the smaller the diameter of the nanocrystalline particle, the higher the compressive strength and the strain at which the maximum stress is reached. A decrease in grain size leads to a reduction in compressive strength, which is associated with the main mechanism of plastic deformation of nanocrystalline nanoparticles, namely grain boundary sliding. At the first stage of deformation, the entire particle structure typically rotates until the maximum value of the stress vector projection onto the preferred slip plane is reached, which, in the case of a nanocrystalline structure, is determined by the mutual orientation of the grain boundaries. Grain boundaries elongated approximately along a single plane represent, in this case, the preferred slip plane.