Discrete breather clusters in strained graphene

Abstract

Molecular-dynamics simulations based on many-body interatomic potentials are conducted to investigate the clusters of discrete breathers in graphene under in-plane homogeneous strain. It is found that the discrete breather clusters can easily be excited when the gap in the phonon density of states is introduced by the homogeneous strain. Clusters of up to four discrete breathers were studied. We demonstrate that such clusters are robust with respect to small perturbations and can have the lifetime of order of 103 oscillation periods. Partial energy exchange between discrete breathers in the clusters was observed under certain conditions. The possible role of discrete breather clusters in formation of lattice defects is discussed.

Discrete breathers above phonon spectrum

“…[3,27] is reversed to the one considered here: the anharmonic in-plane modes with soft anharmonicity are in resonance with out-ofHizhnyakov et al / Letters on materials 6 (1), 2016 pp. 61-72 plane phonons, while out-of-plane TDBs considered here are in resonance with in-plane phonons.…”

“…Note that in strongly-stretched graphene there can exist also in-plane anharmonic localized vibrations (in-plane discrete breathers) [3,27]. It appears (see Ref.…”

“…This makes possible the existence of in-plane soft DBs (discrete breathers) with the frequency in the gap of the phonon spectrum. The authors [3,27] have found that these modes remain relatively stable also when, due to a large stretching, their frequencies get into resonance with out-of-plane phonons.…”

Discrete breathers in metals and ordered alloys

“…DBs can be highly localized, e.g., gap DBs are localized practically on a single atom in graphane and in the NaCl family ionic crystals with considerable difference in atomic masses of anions and cations [18][19][20]; in strained graphene DB is localized on a pair of carbon atoms vibrating out-of-phase [21][22][23]. Such DBs are very easy to excite, e.g., by initial displacement of one or two atoms that have large vibration amplitudes.…”

Effect of discrete breathers on plasticity and strength of crystals

“…Наличие запрещенной зоны в спектре растянутого графена приводит к возмож-ности существования щелевых ДБ большой амплитуды [31][32][33]. На рис.8 а представлена плотность фононных состояний (DOS) для недеформированного графена.…”