It was recalled that interfacial defects could exhibit both dislocation and step-like characteristics. The Burgers vector of such a defect was an invariant topological quantity which could be determined, mathematically or graphically, by means of circuit mapping. The nature of a step could not be directly determined by using such methods, but a new definition of scalar step height was presented here in terms of crystallographic parameters. The partition of a disconnection into a dislocation part and a step part facilitated the analysis of processes such as phase transformations. The dislocation part was associated with the long-range strain field and with shape changes, while the step part was associated with growth-related divergences in diffusional fluxes.

J.P.Hirth, R.C.Pond: Acta Materialia, 1996, 44[12], 4749-63