Description:
<jats:title>Abstract</jats:title><jats:p>The equations of the dynamical scattering theory are derived for a crystal with slowly varying distortion using a method analogous to the WKB method in the quasiclassical approximation. In the zeroth approximation in <jats:italic>h</jats:italic> a system of two equations is obtained. The local dispersion equation determines the eikonals of the wave functions. The equation in the first approximation is derived under the assumption that only one function determines the change of the amplitudes. The system of equations is not complete but allows to determine in absorbing crystals the change of the electron current component which extends along the reflecting plane and is principally apparent in the formation of Borrmann dislocation contrast. The obtained equations are valid as well far from the dislocation as close to it. The contrast of screw dislocations parallel to the crystal surface is considered.</jats:p>