Solubility and segregation of B in paramagnetic fcc Fe

Boron solubility and segregation in paramagnetic (PM) fcc iron have been investigated by means of DFT calculations. The results focus on the Boron site preference in both bulk and coincidence site lattice model $\mathrm{\ensuremath{\Sigma}}5$ (012) GB in fcc Fe and evaluate the validity of different model approaches for modeling the PM state. Boron and PM fcc iron are predicted to form an interstitial solid solution. The PM state model and pressure correction have been introduced into the 0 K DFT calculations to evaluate Boron solubility in fcc Fe as a function of its thermal lattice expansion within the temperature range of 0--1670 K. The relatively high segregation energy of Boron of about $\ensuremath{-}$1.57 eV to both interstitial and substitutional GB sites at 0 K is predicted to substantially decrease with thermal lattice expansion, reaching the value of about $\ensuremath{-}$0.3 eV at the lattice parameter of fcc Fe corresponding to 1670 K. The contribution of the PM state to the segregation energy was found to be of the order of 0.1 eV compared to the nonmagnetic calculations.