... vary linearly with stress and be expressible as a tensor in the very general linear form (3.78) kl where the stress-dependent terms in the sum are relatively small. Similar consider- ations ... distortions in the fixed stress field, so different amounts of work, W, must be done against the stress field during these jumps. The rate of a particular jump in the absence of stress is proportional ... proportional to the exponential factor exp[-Gm/(lcT)], where G" is the free-energy barrier to the 16When the stress is nonuniform and stress gradients exist, the stress will exert a force,...