An MD Simulation of the Atomistic Processes of Movement and Agglomeration of Vacancy Clusters in Nickel at 1300 K

Computer simulations of molecular dynamics (MD) were used to study the clustering of vacancies in nickel. This was carried out in order to investigate the atomistic processes of vacancy agglomeration in irradiated metals. Simulations were carried out using DYNAMO ver. 8.5 code, by implementing the potential of the embedded atom method (EAM). Firstly, a perfect crystal was thermalized at 1300, 1500, 1700 and 1800 K. Next, four triangular vacancy clusters whose sizes were 10 were introduced on the (111) planes at randomly selected positions. MD simulations were performed using a very small time step of outputs to observe the atomistic processes of the movement of each vacancy. It was found that the vacancy clusters moved and agglomerated whilst maintaining the individual clusters. Thus, a vacancy did not evaporate from a cluster to be absorbed into a larger cluster. There were three different processes in the agglomeration of the vacancy clusters. One was an atom caged in a tetrahedral structure of vacancies moved to another lattice site. Another was an atom caged in a octahedral structure of vacancies moved to another lattice site. The other was an atom moved along a (110) row.