The kink chain revisited

Abstract

The equilibrium configuration of a kink chain consisting of kink pairs, formed in a dislocation segment bowing out under the action of an applied stress σ, is determined by deriving an expression for the enthalpy H(σ), taking account of all kink–kink interactions. For a realistic description, instead of the usual 1/r asymptotic potential, the Püschl potential must be used, which does not diverge when two kinks of the same sign approach each other. For a given applied stress σ, above a critical stress there exist, due to geometrical restraints, a number of different bow-out configurations with different numbers of kink pairs and the problem is to find the ‘ground state’, which is the state with the lowest enthalpy. This can only be done by numerical or semi-graphical methods. Since the ground state can only be reached by thermal activation, there is an asymmetry in the forward and backward movement. It is found that in the equilibrium configuration the kinks of the same sign generally accumulate at the two opposite side arms, leaving a longer straight segment in between. When the bow-out height of the kink chain approaches the height resulting from the line tension model, the influence of the long-range back-stress caused by the overall curvature cannot be neglected and it limits the accessible height.