Multi-scale modelling of defect behavior in bcc transition metals and iron alloys for future fusion power plants

A multi-scale materials modelling approach is developed in order to investigate the structure, energy, mobility as well as the dynamical behavior of the neutron-induced defects in bcc transition metals and alloys for future fusion power plants. Our focus is on exploring quantum mechanical effects (directional bonding, magnetism and bond screenings) present in these specific materials. Using density functional theory (DFT) we have generated a comprehensive database of formation energies for self-interstitial atom defects for all bcc TM. We found that the energies of various defect structures in non-magnetic bcc transition metals show a striking systematic trend different to those found in ferromagnetic iron. Our new ab initio database is going to be used to develop genetic and reliable interatomic potentials based on the tight binding approximation. These potentials have been applied for studying the core structure and glide of the (1/2)〈1 1 1〉 screw dislocation bcc transition metals and magnetic properties of point defects in Fe based on Stoner model. A large-scale molecular dynamic cascade simulations based on quantum core effects is also investigated. Finally, one-dimensional analytic solutions for strain fields of interstitial cluster are presented to compare with our predictions of DFT calculations.