Stress effects on stability and diffusion behavior of sulfur impurity in nickel: A first-principles study

A systematic investigation regarding the effect of stress on the stability and diffusion behavior of S impurity in Ni was carried out via first-principles methods. A comparison of the formation energy of S in Ni indicated that S more easily forms as a solution atom with increasing S concentration in Ni supercells, but the binding energy showed that as the concentration of S that dissolved into Ni increased, the structure became less stable. The diffusion barrier via the octahedral-tetrahedral-octahedral site path was always lower than that via the octahedral-octahedral site path. The diffusion barrier of single S decreased with increase in tensile stress. S diffusion accelerated under applied tensile stress, which was disadvantageous in suppressing S retention in Ni. These results implied that even at a low concentration, dissolved S still had a tendency of precipitating from the Ni matrix, to further increase the stability of the system. (C) 2014 Elsevier B. V. All rights reserved