Su-Schrieffer-Heeger model applied to chains of finite length.

We discuss both the ground-state properties and the kink-antikink dynamics of finite conjugated chains, using the Su-Schrieffer-Heeger Hamiltonian with a boundary term added. We establish a clear relationship between model parameters for the case of infinite chains or rings, where one uses periodic boundary conditions, and the case of finite chains for which open boundary conditions are employed. Furthermore, we derive the exact expression for the sound velocity renormalization due to the p-electron-phonon coupling, arrived at earlier heuristically. The suppression of the sound velocity is only exponentially small in the weak-coupling limit. Some numerical studies of the influence of finite chain length and end effects on kink-antikink dynamics are also presented. @S0163-1829~96!03921-5#