A computer simulation study and critical evaluation of the displacement fields and elastic dipole tensors of oxygen and nitrogen in b.c.c. transition metals

Abstract

Abstract In this paper, we analyse the experimental information (elastic dipole tensor, diffuse scattering and static Debye-Waller effect) regarding the displacement field caused by 0 and N interstitials in b.c.c. transition metals. The modified n-body Finnis-Sinclair potentials were used to describe the metal-metal interaction. With these potentials, the displacement field proposed to explain the observed reduction in intensity due to static Debye-Waller effect was found to be incompatible with the experimental elastic dipole tensor. Good compatibility was found between the elastic dipole tensor implied by the diffuse scattering experiments and its experimental values. A significant softening of specific high-symmetry vibrational modes was observed, lending support to the local condensation of a rumpled o phase in the vicinity of an interstitial. Certain paradoxes displayed by a geometrical analysis of the displacement field proposed to account for the diffuse scattering from N in Nb are also discussed.