Computer Experiments on Collisions of Linear and Nonlinear Waves with Defects in Two-Dimensional Square Lattice with Nearest Neighbor and Next Nearest Neighbor Interactions

Abstract

A molecular dynamics computer simulation has been carried out for a two-dimensional (2D) square lattice model crystal. Anharmonic central forces up to the third order are considered for the nearest neighbor and next nearest neighbor interatomic interactions. Pulse input displacements are applied simultaneously to all of the edge atoms at one end of the model crystal, and displacements, velocities, and energies of all atoms in the crystal are calculated as a function of time. Two types of wave are seen in the crystal depending on the excitation conditions. When the input pulse is small, the wave has characteristics of ''phonon''. When the input pulse is large, it has characteristics of ''soliton''. A slit-shaped or linear array of defect atoms is placed at the center of the crystal. The waves are scattered by the defect atoms. The dependences of the scattering on the mass of the defect atoms, the interatomic interaction parameters, and the size of the opening of the slit are studied. The experimental results are represented in 2D colored maps.