Ab initio modelling of defect properties with substitutional and interstitials elements in steels and Zr alloys

In alloys, the different elements interact with each other as well as with the various defects present: point defects or extended defects (stacking faults, dislocations, grain boundaries). These interactions are responsible for the elementary mechanisms governing the kinetics of the system, and they are among the key parameters to model the time evolution of the microstructure, under ageing or irradiation. Indeed the microstructure properties are directly linked to the chemical interactions between the different constituting elements, and these defects. Ab initio methods allow to determine properties such as defect formation, binding or migration energies. These crucial quantities can shed light on the various mechanisms involved in the evolution of the microstructure as well as be used as input for various models. In this article, data obtained by ab initio calculation of point defects (vacancies and self-interstitial atoms, foreign interstitial defects (C, N, H and He) in different matrix element (Fe and Zr) as well as of some substitutional elements (Cu, Ni, Mn, Si, Cr and P ...)) in bcc Fe will be presented and discussed. When available, comparison with experimental data will be made in order to assess the validity of the results. The link between the obtained atomic quantities and the related consequences on the macroscopic properties will be discussed