Discrete breathers properties obtained from ab initio calculations in graphene and graphane

Abstract

The density functional method was used for the simulation of discrete breathers in graphane (fully hydrogenated graphene) and strained graphene. It is demonstrated that breathers can exist with frequencies lying in the gap of the phonon spectrum of both systems. The gap in graphane is a consequence of high mass difference between carbon and hydrogen atoms, while in graphene the gap is induced by uniaxial tension of carbon layer in the "zigzag" direction (axes X). Breather core atoms in graphane are moving along Z direction which is perpendicular to the carbon sheet. In graphene discrete breathers are polarized in the "armchair" direction (axis Y). In both systems breathers are highly localized dynamical objects. The frequency on amplitude dependence found for breathers possess soft nonlinearity type. The results are of fundamental importance, as far as for discrete breathers in crystals molecular dynamics calculations based on empirical potentials should be revised by means of more reliable methods.

Interaction of longitudinal phonons with discrete breather in strained graphene

“…Of particular interest is the interaction between phonons and other nonlinear lattice excitations, termed as either discrete breathers (DB) or intrinsic localized modes (ILM) [43,44,45,46,47]. Properties of DB in graphene and carbon nanotubes have been studied in a number of works [48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66]. In theoretical models, DB [67,68,69,70] and solitons [71] have been shown to affect thermal transport in certain nonlinear chains.…”