Ab initio calculations of vacancy interactions with solute atoms in bcc Fe

Solute Cu plays a major role in the embrittlement of reactor pressure vessel (RPV) steels under radiation. In RPV steels and dilute FeCu alloys, the tomographic atom probe has revealed the formation of Cu atmospheres under neutron flux. More recently the role of other solutes such as Ni, Mn and Si which are also within the atmospheres has been put forward. It is thus very important to characterise the interactions of these solutes with radiation-induced point defects in order to understand the elementary mechanisms behind the formation of these atmospheres. We have investigated by ab initio calculations based on the density functional theory the interactions of point defects in dilute FeX alloys (X = Cu, Mn, Ni or Si). The structure of X-vacancy complexes has been determined, as well as their binding energies. Their relative stability is discussed and compared to experimental results obtained with model alloys.