By using a formulation which was based upon anisotropic elasticity, the core energy and Peierls stress of the a/2[111] screw dislocation in body-centered cubic Mo were determined at T = 0. It was shown that a proper definition of the core energy involved choosing a reference direction, a, and a reference radius, r0, in order to describe the dislocation dipole rotation and dilatation, respectively, in the asymptotic expansion of the total energy. The core energy was deduced from atomistic calculations, for super-cells which contained a single dislocation dipole with periodic boundary conditions, in a manner that consistently treated the effects of image interactions. As a result, the core energy was invariant with respect to the super-cell size and shape, image-sum aspect ratio and dislocation dipole distance and orientation. By using an environment-dependent tight-binding model, values of 0.371eV/Å at a = <11¯2> and r0 = b and 3.8GPa were obtained for the energy of a core with zero polarity and Peierls stress for simple shear in (¯110)<111>, respectively. This was compared with the 0.300eV/Å and 2.4GPa obtained by using an empirical many-body potential for a polarized core. The results suggested that the high Peierls stress of screw dislocation was due to a transition from non-planar to planar cores; rather than being a direct effect of the equilibrium core polarity.

Core Energy and Peierls Stress of a Screw Dislocation in BCC Molybdenum - a Periodic-Cell Tight-Binding Study. J.Li, C.Z.Wang, J.P.Chang, W.Cai, V.V.Bulatov, K.M.Ho, S.Yip: Physical Review B, 2004, 70[10], 104113 (8pp)