Shape of Nucleus Domain Anchored to a Screw Dislocation in Ferroelectric Crystal

The elastic deformation around a screw dislocation in a ferroelectric crystal, which has a spontaneous shear strain in ferroelectric state was solved using the relaxation method, taking into account the nonlinear stress-strain relationship of the ferroelectrics. The result turned out to contain a discontinuity corresponding to the domain boundary. This domain is plate-like in the absence of the external field but becomes wedge-shaped by application of a field. The relaxation process is analogous to the one used in solving ordinary Laplace equation but differs in that the stress is put to zero when the strain is less than a certain magnitude. The calculation took a few hours on a digital computer PC–1.