Long range vibrational interactions in linear carbon chains

Carbon linear chains are interesting p-conjugated systems where long range interactions take place due to the delocalized nature of p electrons. In this contribution the vibrational force field of hydrogen terminated oligoynes of increasing chain lengths is investigated by means of first-principles calculations. In particular it is shown that the interaction force constants between CC stretching coordinates decreases slowly with the distance between the bonds considered. The consequence of such a slow decrease with respect to the phonon dispersion of an infinite chain is discussed.