Ab initio tensile tests of grain boundaries in the fcc crystals of Ni and Co with segregated sp-impurities

Models of Σ5(210) grain boundaries in crystals of fcc Ni and fcc Co with segregated sp-impurities (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb, and Te) have been subjected to ab initio computational tensile tests. Two models of deformation (rigid grain shift and uniaxial loading) have been considered and their results have been compared. The results reveal striking differences in predictions from the models. Poisson contraction included in the model of uniaxial loading remarkably reduces the computed strength values but, unlike the rigid grain shift, predicts an enhancement of the grain boundary strength due to the presence of impurities (particularly those segregated in interstitial positions). These different predictions are discussed in terms of the effect of transverse stresses on the computed strength values.