The effect of electron correlation on bond alternation of polymers is clarified by calculation of the electron correlation function. Instead of the extended Hubbard model, we start from the full Coulomb interaction with any strength and range. In contrast to the other theories, our results disclose the following: (1) When the interaction range is short the bond alternation monotonically decreases with increasing strength. (2) Extension of the interaction range will increase bond alternation. (3) If the electron-lattice coupling is strong, bond alternation is suppressed by electron repulsion; but if it is weak the bond alternation is mainly caused by repulsion.

• Received 27 January 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.831