Modeling the Surface Structure and Stability of α-Quartz

Abstract

Atomistic simulation techniques were employed to model the {0001}, {101̄0}, {101̄1}, and {101̄1̄} surfaces of α-quartz. The effect of associative and dissociative adsorption of water onto the surface structure is studied, and it is found that associative adsorption of water onto the {101̄1} surface induces the formation of Si−O−Si bridges, similar to those found on the very stable unhydrated {0001} surface. Dissociative adsorption of water is energetically favorable on all four surfaces, and hydration energies agree with experiment. Surface H+ ions were replaced by Na+ ions in two consecutive steps. Replacing only half the surface H+ ions by Na+ ions is energetically favorable, but when all H+ ions are replaced, the surface energies and hence stabilities of the four surfaces diverge widely, which has implications for the crystal morphology. On the {101̄1̄} surface Na−O−Na bridges are formed, which has a stabilizing effect.