  In dislocation-free martensites the components of the elastic strain tensor
are constrained by the Saint-Venant compatibility condition which guarantees
continuity of the body during external loading. However, in dislocated
materials the plastic part of the distortion tensor introduces a displacement
mismatch that is removed by elastic relaxation. The elastic strains are then no
longer compatible in the sense of the Saint-Venant law and the ensuing
incompatibility tensor is shown to be proportional to the gradients of the Nye
dislocation density tensor. We demonstrate that the presence of this
incompatibility gives rise to an additional long-range contribution in the
inhomogeneous part of the Landau energy functional and to the corresponding
stress fields. Competition amongst the local and long-range interactions
results in frustration in the evolving order parameter (elastic) texture. We
show how the Peach-Koehler forces and stress fields for any distribution of
dislocations in arbitrarily anisotropic media can be calculated and employed in
a Fokker-Planck dynamics for the dislocation density. This approach represents
a self-consistent scheme that yields the evolutions of both the order parameter
field and the continuous dislocation density. We illustrate our method by
studying the effects of dislocations on microstructure, particularly twinned
domain walls, in an Fe-Pd alloy undergoing a martensitic transformation.
