Dynamics of supersonic N-crowdions in fcc metals: Reports in Mechanical Engineering

Crowdion is an interstitial atom located in a close-packed atomic row. It is an important point defect participating in relaxation processes occurring in metals and alloys under irradiation, effectively transferring mass and energy. In recent works of the authors, the concept of a supersonic crowdion was extended to a supersonic N-crowdion, in which not one, but N atoms move with high speed along a close-packed row. An experimental study of interstitial atoms moving along a crystal lattice at supersonic speeds encounters serious technical difficulties, and the most effective method for studying them is the molecular dynamics method. In this regard, a numerical study of dynamics of supersonic crowdions in metals is very important. In the present study, the molecular dynamics method was used to analyze the motion of supersonic 1- and 2-crowdions in fcc metals Ni, Al, Cu. The calculations were carried out using the LAMMPS software package and many-body potentials. The N-crowdion was excited by setting the same initial velocity to N neighboring atoms along a close-packed row. It was found that the mean free path of a 2-crowdion in pure metals can reach values that are 3 times greater than the mean free path of a 1-crowdion having the same initial energy. The results obtained indicate a higher efficiency of 2-crowdions in mass transfer in the studied metals. In further works, the possibility of launching supersonic 2-crowdions by bombarding the crystal surface with biatomic molecules will be analyzed.