MOLECULAR DYNAMIC MODELING OF PARTICLE ADHESION

Molecular dynamic modeling was used to study the interactions between nanometer size two-dimensional particles in proximity to the surface o f a two-dimensional crystal composed of the same material. The modelin g was conducted by using triangular lattices of atoms that interact th rough a Lennard-Jones potential. The atoms were configured such that t he particle consisted of a circle with 463 atoms. The crystal was in t he shape of a rectangle and contained 442 atoms. The system was assume d to have periodic boundary conditions. It was first allowed to equili brate with an assumed dimensionless kinetic energy per atom of 0.2 eps ilon. Subsequently, the particle was made to approach the surface at a velocity of 0.387 sigma/t (corresponding to 6.25 m/s for argon), whic h is small compared with the speed of sound in the material. The appro ach was conducted in two modes:(1) centroidal displacement control at constant temperature and (2) free flight at the same intercentroidal v elocity of approach. For each case, the intercentroidal distance, velo city, and forces were determined as the particle approached, made cont act, and relaxed into the surface. The computation followed the respon se of the system for a total of 11900 iterations (corresponding to 2.5 4 ns for argon). The particles and surfaces were found to deform befor e, during and after impact. Surface forces were sufficiently large to prevent the particles from separating from the substrate following the collision. The excess energy generated acoustic waves and lattice def ects. The geometry of the system at selected times was used to illustr ate the deformations that occur. Results based on a molecular statics approach are also presented for comparison with analytical models base d on potentials. Finally, preliminary results of a particle being remo ved from the substrate are presented.