Domain wall diffusion and domain wall softening

Abstract

A number of experimental and computational studies of materials haveshown that transport rates in domain walls may significantly differ fromthose in the bulk. One possible explanation for enhanced transport in adomain wall is that the domain wall is elastically soft with respect tothe bulk. We investigate the softening of a ferroelastic domain wall in asimple, generic model. We calculate saddle point energies of solute atoms inthe bulk and domain wall, using a geometry such that variation in thesaddle point energy cannot be attributed to the structural differencesof the bulk and the wall, but must instead be attributed to softeningof the wall. Our results show a reduction of the saddle point energy inthe wall, thus indicating that, in this model at least, domain walls areelastically soft compared with the bulk. A simple analysis based on anEinstein model allows us to explain the observed softening of the wall.