Starting from the relationship between brittleness and a negative Cauchy pressure of elastic constants in materials within the so-called Harris-Foulkes approximation to density functional theory, the importance of the generic form of interatomic potentials in deducing the correct Cauchy pressure was considered. The latter was then important in predicting the dislocation properties of face-centered cubic iridium and explaining experimental observations of its intrinsic brittleness. The behaviour of the ½[111] screw dislocation which controlled plastic deformation in body-centered cubic metals was investigated using atomistic simulations. The atomic phenomena associated with the non-planar core structure of dislocations in body-centered cubic iron were deduced from the Stoner tight-binding bond model. Crucial results came from accurate evaluation of the forces implicated in charge neutrality conditions when treating spin-polarized dependence in electronic structure calculations. Like density functional theory studies, the magnetic bond-order potentials predicted a non-degenerate core structure for screw dislocations in Fe. Finally, a new analytical expression was derived for the migration energy barrier to the one-dimensional motion of crowdions; which were the most stable self-interstitial atom defects predicted by the present density functional theory calculations. The latter study was strongly supported by observations of the 1D diffusion of nm-sized dislocation loops.

Dislocation Driven Problems in Atomistic Modelling of Materials. N.M.Duc, M.Mrovec, S.P.Fitzgerald: Materials Transactions, 2008, 49[11], 2497-506