Abstract
Defects, defect interactions, and defect dynamics in solids created by fast neutrons are known to
have significant impact on the performance and lifetime of structural materials. A fundamental
understanding of the radiation damage effects in solids is therefore of great importance in assisting
the development of improved materials - materials with ultrahigh strength, toughness, and radiation
resistance. In this presentation, we show our recent theoretical investigation on the magnetic
structure evolution of bulk iron in the region of the radiation defects. We applied a linear scaling
ab-initio method based on density functional theory with local spin density approximation, namely
the locally self-consistent multiple scattering method (LSMS), to the study of magnetic moment
distributions in a cascade at the damage peak and for a series of time steps as the interstitials and
vacancies recombined. Atomic positions correspond to those in a low energy cascade in a 10|000
atom sample, in which the primary damage state and the evolution of all defects produced were
simulated using molecular dynamics with empirical, embedded-atom inter-atomic potentials. We
will discuss how a region of affected moments expands and then recedes in response to a cascade
evolution.
