Influence of Elastic Stiffness and Surface Adhesion on Bouncing of Nanoparticles

Granular collisions are characterized by a threshold velocity, separating the low-velocity regime of grain sticking from the high-velocity regime of grain bouncing: the bouncing velocity, v (b). This parameter is particularly important for nanograins and has applications for instance in astrophysics where it enters the description of collisional dust aggregation. Analytic estimates are based on the macroscopic Johnson-Kendall-Roberts (JKR) theory, which predicts the dependence of v (b) on the radius, elastic stiffness, and surface adhesion of grains. Here, we perform atomistic simulations with model potentials that allow us to test these dependencies for nanograin collisions. Our results not only show that JKR describes the dependence on materials parameters qualitatively well, but also point at considerable quantitative deviations. These are the most pronounced for small adhesion, where elastic stiffness does not influence the value of the bouncing velocity.