Study of the influence of various factors on the melting and crystallization processes of nickel nanoparticles using molecular dynamics simulation

Using molecular dynamics modeling, the influence of various factors on the melting and crystallization processes of nickel nanoparticles was studied. The effect of the nanoparticle size, the rate of the temperature change during heating or cooling, the presence of structural defects in the nanoparticles and the impurity atoms of carbon and hydrogen were considered. It was demonstrated that the stability range of the solid phase, as well as the melting and crystallization temperatures of metallic nanoparticles, can be controlled by several methods, including varying the nanoparticle size, the density of structural defects, and the concentration of impurities. The work shows that the melting and crystallization temperatures of nanoparticles are inversely proportional to their diameter. The presence of structural defects in the nanoparticles and the impurities of light elements contributes to a decrease in their melting temperature. The main quantitative criterion determining the effect of defects on the melting point depression of nanoparticles is the excess energy, defined as the difference between the free energy of the considered structure and that of the same number of atoms in an ideal crystal. The melting temperature of the nanoparticles decreases linearly with increasing excess energy. By introducing impurities and increasing the cooling rate, it is possible not only to control the crystallization temperature of nanoparticles but also to control the defect density and the potential energy stored in them within the final nanoparticle structure.