Computer Experiments on Propagation of Nonlinear Waves in Model Crystals with Next-Nearest-Neighbor Atomic Interactions

Molecular dynamics computer simulations were performed for one-dimensional (1D) and two-dimensional (2D) anharmonic mass-spring model crystals. Anharmonic potentials up to the fourth order were taken into account. Central forces were considered between the nearest-neighbor (nn) and the next-nearest-neighbor (nnn) atoms. The ratio of the potential between the nnn atoms to the potential between the nn atoms was varied. An input pulse displacement was given to definite atoms in the crystal and induced displacements and velocities of all atoms were computed. Propagating solitons were produced as atomic excitations and the energy of the excitation was sharply concentrated in the solitons. Simulations were mainly carried out to study the influence of interatomic interactions in the crystal, short-range or long-range in character, upon the soliton production.