Dynamics of new class of M-solitons and M-crowdions, here M = 3 is the number of adjacent close-packed atomic rows where the atoms move, are studied in two-dimensional triangular Morse lattice using classical molecular dynamics simulations. 3-solitons/3-crowdions are excited by giving initial velocities to the three atoms in three neighboring close-packed atomic rows along the rows. Different relations between the initial velocities are considered: all three initial velocities are equal, initial velocity for the middle atom is lower than for the outermost atoms, and all three velocities are different. During propagation of a 3-soliton the atoms do not overcome potential barrier and relax back to their original lattice sites. Propagation of a 3-crowdion results in the shift of the atoms to the neighboring lattice sites along the direction of movement. It is found that propagation of 3-soliton/3-crowdion clusters is associated with the energy exchange between the adjacent atomic rows. The ratio between the initial energies, at which the maximum energy exchange occurs, is determined. The energy is transferred from the high-energy atomic rows to the low-energy one. In the case when initial velocities in all three rows are different, the dynamics of 3-soliton/3-crowdion clusters is unstable. Obtained results allow to better understand the dynamics of interstitial defect clusters.
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