Supersonic crowdion clusters in 2D Morse lattice

Abstract

Abstract For the first time, the class of simple N-crowdions is expanded to M × N -crowdions, dynamics of which is investigated in two-dimensional triangular Morse lattice by means of molecular dynamics simulations. The M × N -crowdions are excited by giving initial velocity V 0 to the chosen M × N block of atoms along a close-packed direction. In the notations here N is the number of neighboring atoms in one close-packed row and M is the number of neighboring rows. The 2 × 1 , 2 × 2 and 2 × 4 -crowdions are chosen for consideration. It is found that the 2 × 1 and 2 × 2 -crowdions demonstrate stable dynamics, while the 2 × 2 -crowdions propagate longer distances and need less energy for their excitation in comparison with the 2 × 1 and classical 1 × 1 -crowdions. Unlike the first two, the 2 × 4 -crowdions are unstable and transform very quickly into the 2 × 2 -crowdions by losing interstitials, which are quasi-mobile and inclined by 60° with respect to the direction of the initial velocity vector. Maximal distances travelled by the crowdions as functions of initial velocity are calculated. The 2 × 2 and 2 × 4 -crowdions are found to be the most effective in mass transfer. The defect structure arising in the crystal as a result of initiation of M × N -crowdions and its dependence on the initial velocity is discussed.