The vast majority of DFT calculations on radiation defects in metallic materials have been performed in body-centered cubic (bcc) iron-based materials, for obvious application reasons of ferritic steels but also because of the more severe shortcoming of predic­tions based only on empirical potentials. A number of accurate estimates of energies of formation and migration of self-interstitial and vacancy defects as well as small defect clusters and solute-vacancy or solute-interstitial complexes have been obtained.

DFT calculations have been intensively used to predict atomistic defect configurations and also tran­sition pathways. An overview of these results is pre­sented below, complete with examples in other bcc transition metals, in particular tungsten, as well as hcp-Zr. These examples illustrate how DFT data have changed the more or less admitted energy land­scape of these defects and also how they are used to improve empirical potentials. In the final part of this chapter, a brief overview of typical works on disloca­tions (in iron) is presented.