Discrete optic breathers in zigzag chain: analytical study and computer simulation

Abstract

We present analytical and numerical study of discrete breathers identified as localized deformations of valence angles accompanied by change of valence bonds in crystalline polyethylene (PE). It is shown that such breathers can exist inside the optic wave number band and can propagate along the macromolecule chain with subsonic velocities. Analytical results are confirmed by numerical simulation using Molecular Dynamics procedure. We examine also stability of the breathers relative to thermal excitations and mutual collisions as well as to collisions with acoustic non-topological and topological solitons. The conditions of breathers existence depend strongly on their generating frequency, relationship between stiffnesses of valence bonds and valence angles as well as on type of nonlinear characteristics of intrachain interactions.