Molecular dynamics simulations of nanoparticle-surface collisions in crystalline silicon

We present a microscopic description for the impacting process of silicon nanospheres onto a silicon substrate. In spite of the relatively low energy regime considered (up to 1 eV/atom), the impacting process exhibits a rich behavior: A rigid Hertzian model is valid for speeds below 500 m/s, while a quasi-ellipsoidal deformation regime emerges at larger speeds. Furthermore, for speeds up to 1000 m/s the particle undergoes a soft landing and creates a long-lived coherent surface phonon. Higher speeds lead to a rapid attenuation of the coherent phonon due to a partial diamond cubic to β-tin phase transformation occurring in the particle.