Gap discrete breathers in two-component three-dimensional and two-dimensional crystals with Morse interatomic potentials

The properties of gap discrete breathers in three-dimensional and two-dimensional crystals of the composition $A_3 B$ with interatomic bonds described by the Morse potential have been investigated by the molecular dynamics method for different ratios between the masses of components $m_A/m_B$. The transition to a thermal equilibrium from a state far from equilibrium has been studied for the two-dimensional crystal. In this case, a short-wavelength phonon vibrational mode is excited in the crystal. This mode appears to be modulationally unstable for not too small amplitudes. During the transition to the state characterized by a uniform energy distribution between all vibrational modes of the crystal, the energy is localized in the form of gap discrete breathers, which exist in time intervals that exceed their oscillation period by several orders of magnitude.