Molecular dynamics study of melting and crystallization of nickel nanoparticles with carbon impurity

Molecular dynamics simulations were used to investigate the melting and crystallization processes of nickel nanoparticles and the influence of carbon impurities on these processes. It is shown that melting and crystallization temperatures are inversely proportional to particle diameter: as particle size decreases and the proportion of free surface area increases, melting temperatures during heating and crystallization temperatures during cooling decrease. The presence of carbon impurity atoms reduces both melting and crystallization temperatures. Carbon atoms often formed clusters within the metal consisting of several carbon atoms, which distorted the nickel crystalline lattice around them, leading to earlier melting of the metal. During crystallization as a result of cooling from the melt, impurity carbon atoms, especially clusters of them, tended to anchor primarily at grain boundaries and triple junctions.