Role of intrasurface hydrogen bonding on silica dissolution

A recently formulated reactive Monte Carlo (RxMC) algorithm has been applied to determine the differential dissolution probability in topographically distinct crystallographic faces of -cristobalite. Although the contribution of edge, kink, and step sites to the overall dissolution from a crystal is well established, the effect of hydrogen bonding on flat terrace sites is less understood. In an earlier study (J. Phys. Chem. 111, 5169, 2007), 40 β-cristobalite surfaces were shown to have distinct intrasurface hydrogen bonding patterns between the hydroxylated surface groups. This study is an extension of the previous work with the aim to identify the role intrasurface hydrogen bonding has toward overall dissolution from these surfaces. Five surfaces have been chosen with varying ratios of Q² (two surface OH groups per Si site) and Q³ (one surface OH group per Si site) groups. The results successfully show that pure Q² {100} terrace sites with intrasurface hydrogen are less reactive than non-hydrogen bonded pure Q ³ {111} terrace sites. The newly formulated R×MC algorithm for silica-water dissolution highlights the unique features of the terrace sites and distinguishes one surface from the other.