A comparison of crystal defect models

The anisotropic elasticity theory, direct-space relaxation and lattice statics approaches to modelling crystal defects are compared with respect to the displacement fields about 〈111〉 screw dislocations in body-centred cubic metals. Lattice statics and continuum calculations were performed for models of α-iron, potassium and several hypothetical b.c.c. crystals with varying elastic anisotropy and atomic interaction ranges. The differences between continuum and lattice statics displacements are generally small in magnitude and converge rapidly with distance from the core. The differences increase with the degree of anisotropy. There is no apparent relationship between the rate of lattice–continuum convergence and the range of atomic interactions in crystal models with the same anisotropy. Neither continuum nor lattice statics models exhibit the three-fold faulted nature of the core region predicted by direct-space calculations for α-iron, though the lattice statics results exhibit the same symmetry.