The structure and dynamics of energetic displacement cascades in copper and nickel. A molecular dynamics computer simulation study

The primary state of damage present in a solid as a result of particle irradiation has been a topic of interest to the physics and materials research community over the last forty years. Energetic displacement cascades resulting from the heavy ion irradiation of a solid play a prominent role in radiation damage and non-equilibrium processing of materials; however, their study has been hampered by the small size ({dollar}approx{dollar}10{dollar}sp{lcub}-20{rcub}{dollar} cm{dollar}sp3{dollar}) and short lifetime ({dollar}approx{dollar}10{dollar}sp{lcub}-11{rcub}{dollar} s) as well as by their highly non-homogeneous nature.; In this work, the molecular dynamics computer simulation technique is employed to study the structure and dynamics of energetic displacement cascades in Cu and Ni. The atomic interactions in Cu were described with the use of the Gibson II form of the Born-Mayer pair potential while for Ni the Johnson-Erginsoy pair potential was employed. Calculations were also carried out with the use of the embedded atom method many-body potentials.; The results provide the first detailed microscopic description of the evolution of the cascade. We show for the first time, that a process akin to melting takes place in the core of the cascade. Atomic mixing, point defect production and point defect agglomeration, all processes directly related to the evolution of the cascade, are then explained in terms of a simple model in which the liquid-like nature of the cascade plays a dominant role in determining the primary state of damage.