NONLINEAR EXCITATIONS IN THE POLARIZATION LAYERS OF HTSCS

For layered cuprate HTSC's, various deformation potentials are calculated on the basis of LDA-density functional theory. The special role of apec and chain oxygens is stressed. Using these results bipolarons within a ''diatomic'' one-dimensional model for the MxOy chains present in the doping subsystem of the HTSC's (M = Cu, Bi, TI) are considered in connection with a recently proposed s-channel mechanism.