The effect of collisions on the chemomechanics of ice-covered silica slabs: a molecular dynamics study

Using molecular dynamics simulation and the REAX potential, we study the collision of two planar silica surfaces covered by water ice. Without the ice cover, the two surfaces stick at all velocities investigated (160-1800 m s^-1), due to the formation of chemical bonds between the colliding surfaces. A narrow ice cover - here of thickness 2 nm - prevents the sticking above a characteristic velocity, the bouncing velocity ν_b. During the collision, reactions occur at the silica-water interface; in particular, water molecules are dissociated and silanols are formed at the surface of the silica slabs. Passivation of the silica surface by H atoms is of little consequence to the magnitude of v_b but reduces the number of surface reactions occurring.