  Coherent bremsstrahlung of high energy electrons moving in a
three-dimensional imperfect periodic lattice consisting of a complicated system
of atoms is considered. On the basis of the normalized probability density
function of the distribution of atomic centers in the fundamental cell the
relations describing coherent and incoherent contributions into cross sections
are obtained. In particular, the cross section of coherent bremsstrahlung in
complex polyatomic single crystals is found.
  The peculiarities of formation and possibilities of utilization of coherent
processes are discussed.
