Dynamic contact behaviours involving crystalline diamond nanospheres

Abstract

Contact behaviours at the ultrasmall nanoscale are sensitively dependent on the atomic arrangement and play an import role in engineering the mechanical and thermal or electrical conductivity properties of nanodevices. Although effect of atomic structure on the nanoscale and quasi-static contact law has been explored, nonetheless such effect under the condition of high-speed nanoscale contact has been rarely touched upon. In this work, high speed contact behaviours between diamond nanospheres have been studied using fully atomistic molecular dynamics simulations. The effect of initial relative impact velocity on contact force, contact radius and mean contact stress were first examined, indicating that all of them are largely independent of initial relative impact velocity. It was confirmed that either contact radius or maximum contact radius calculated from molecular simulations are higher than those from continuum predictions. Mean contact stress, contact radius exhibit a staircase-shaped hike with increasing either strain or normal displacement, indicating the nature of regular discrete atomic arrangement of crystalline structure. Contact radius is characteristics of staircase-shaped hike with increasing normal displacement, but the magnitude of contact radius is prone to approach the Hertzian prediction with increasing the particle size. At the atomic level for high-speed contact mechanics, the correlation between contact radius and number of atoms in contact obey approximately sub-linear relationship with jumps or pop-in because of surface steps. The staircase-shaped discrete atomic arrangement exerts more pronounced influence on the contact behaviours as compared with the flat-shaped ones. Either mean contact stress or contact radius exhibits several recurring “pop-in” or “plateau region” at a periodic interval of about the radius of carbon atom. This work could strengthen the capability of solving the problems experienced in practical applications where high-speed nanoparticle collisions are involved, such as magnetron sputtering, energetic nanoparticle's explosion.