Discrete breathers in a polyethylene chain

The existence of discrete breathers or intrinsic localized modes (localized periodic oscillations of transzigzag) is shown. In the localization region periodic contraction-extension of valence C-C bonds occurs, which is accompanied by decrease-increase of valence angles. The concentration of thermally activated formation of discrete breathers in the chain has to increase when temperature grows. However, the breather in thermalized chain has a finite time of life decreasing with growth of the temperature. It is a reason for nonmonotonous dependence of concentration breathers upon temperature T. Concentration increases for small temperature (T<200 K) and decreases for large temperature (T>200 K) with maximal magnitude for T=200 K. One can identify the revealed breathers as a unique type of stable localized periodic elementary excitation in thermalized polymer crystal existing even for sufficiently small temperature and contributing essentially to heat capacity.