The effect of surface geometry on collisions between nanoparticles

TL;DR

This study uses molecular dynamics to investigate how different surface geometries of nanoparticles affect impact forces during collisions, revealing deviations from classical Hertzian behavior based on surface type.

Contribution

It demonstrates how nanoparticle surface geometry influences impact force behavior, highlighting deviations from Hertzian contact mechanics for facets, edges, and amorphous surfaces.

Findings

Facet contacts do not expand contact area, leading to non-Hertz impact force.

Edge and amorphous contacts recover Hertz-like behavior with n=1.5.

Surface geometry affects the maintenance of nonlinear dynamic phenomena.

Abstract

In this molecular dynamics study, we examine the local surface geometric effects of the normal impact force between two approximately spherical nanoparticles that collide in a vacuum. Three types of surface geometries, facets, sharp crystal edges, and amorphous surfaces of nanoparticles with radii R < 10 nm are considered, and the impact force is compared with its macroscopic counterpart described by a nonlinear contact force, FN proportional to D with n = 3/2 derived by Hertz (1881), where D is the overlap induced by elastic compression. We study the surface geometry-dependent impact force. For facet-facet impact, the mutual contact surface area does not expand due to the large facet surface, and this in turn leads to a non-Hertz impact force, n < 3/2. A Hertz-like contact force, n = 1.5, is recovered in the edge contact and in the amorphous surface contact, allowing expansion of the mutual contact surface area. The results suggest that collisions of amorphous nanoparticles or nanoparticles with sharp edges may maintain dynamic phenomena, such as breathers and solitary waves, originating from the nonlinear contact force.