Computer Experiments on Scattering of Atomic Excitations by Defects in Model Crystals

A molecular dynamics computer simulation has been carried out for a monatomic, anharmonic, and two-dimensional hexagonal model crystal. Central forces between the nearest neighbor atoms and anharmonic forces up to the third order are considered. Pulse input displacements are applied to the line of atoms at one end of a rectangular crystal, and the atomic excitations propagating in the crystal are observed. The excitations are shown to be phonons or solitons when the applied pulse is small or large, respectively. A mass defect – an atom of which the mass is lighter or heavier than that of the lattice atoms – is placed near the center of the crystal. The excitation is scattered by the defect, and the simulations are made for various cases of large and small inputs, and light and heavy mass defects. The obtained results are represented using two-dimensional maps. The intention of the study and the significance of the results are briefly discussed.