Soliton dynamics and Peierls-Nabarro barrier in a discrete molecular chain

We investigate the motion of a self-localized quasiparticle in a discrete l attice taking into account the interaction of the quasiparticle with the vi brations of the lattice. Using an original method to control the velocity o f solitonlike excitations in a discrete system, the dependence of their vel ocity, momentum, and energy on the carrying wave vector is analyzed. The ve locity of the solitonlike excitations is found to saturate at wave vectors below those predicted by continuum models. This is as found in experimental observations. Also, the properties of the Peierls-Nabarro relief, caused b y the lattice discreteness, and pinning of a soliton by this barrier, are s tudied. The influence of the initial condition on the Peierls-Nabarro barri er and soliton motion is investigated. For low-width solitons, a critical v alue of the wave vector is needed to overcome the Peierls-Nabarro barrier.