Ice-grain impact on a rough amorphous silica surface

Using molecular dynamics simulation, we analyze the collision between a water-ice grain and a silica surface. Both a flat and porous surfaces are studied. We find that the presence of pores in the silica sample and the induced roughness of the silica surface significantly influence the collision outcome. The presence of pores on the surface increases the contact area of the colliding grain with the silica sample, and consequently also the number of reaction products, i.e., water dissociation products and silanol groups formed at the silica surface. The effect is maximum if the pore size is of the order of the grain radius. In addition, the presence of pores on the surface allows for the penetration of water molecules under the surface, molecule ejection from the colliding ice grain is enhanced, and dissipation of the collision energy into the sample is hindered.