  We perform first principles, multiconfiguration calculations on clusters
including several CuO$_6$ octahedra and study the ground-state electron
distribution and electron--lattice couplings when holes are added to the
undoped $d^9 p^6$ configuration. We find that the so-called Zhang--Rice state
on a single CuO$_4$ plaquette is nearly degenerate with a state whose leading
configuration is of the form Cu $d^9$-- O $p^5$-- Cu $d^9$. A strong coupling
between the electronic and nuclear motion gives rise to large inter-site charge
transfer effects for half-breathing displacements of the oxygen ions. Under the
assumption of charge segregation into alternating hole-free and hole-rich
stripes of Goodenough \cite{jbg_02,jbg_03}, our results seem to support the
vibronic mechanism and the traveling charge-density wave model from
Refs.\cite{jbg_02,jbg_03} for the superconductivity in copper oxides.
