Computational study of radiation damage and impurity effects in iron based alloys
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Molecular dynamics techniques are used to explore metals at an atomic level. The focus of the studies is the effects of irradiation on a metallic system. Ion surface bombardment effects, bulk cascades and interaction with voids and bubbles in bulk are studied. In the first section a study of a copper <110> surface being bombarded by low energy argon ions is conducted. Molecular dynamics simulations were used to study the surface impact crater formation and the damage caused in the surrounding area. Another group had previously performed experimental measurements on the same system. The simulation data is compared to experiment, in order to validate the molecular dynamics technique. Additionally, information about the formation of the craters at time scales inaccessible to experiment can be gained. In the next section bulk radiation induced cascades in BCC iron are considered. Cascades of energy 1 keV, 2 keV, and 5 keV are initiated in the bulk of the material and the damage yields studied. Cascades are also studied in proximity to voids and helium bubbles in the bulk. The damage formation processes and damage yields in these cascades is analysed. A mechanism that allowed voids to be ballistically moved by the cascade was observed. To further explore this an object kinetic Monte Carlo model was written to simulate the effects of this motion on the diffusion of the voids. The final section is a study of transition metals as alloying elements in BCC iron. This system is of interest as it would be a model for various steels used in construction and shielding. A set of potentials describing iron with low concentrations of transition metals has previously been developed by a different group. These potentials were implemented in the molecular dynamics code. The equilibrium properties of various alloys are explored by implementing a Metropolis algorithm to minimise the Gibbs free energy of the system. Various binary and tertiary alloys are analysed and compared with experimental values in the literature. The attraction of the elements to voids present in the system is also studied.