The first‐principles molecular dynamics study of quartz–water interface

Abstract

By first‐principles molecular dynamics, we have investigated the interaction of quartz (0001) surface with liquid water for two different fresh silica cleavages. The first type of cleavage is terminated by Si(O)2 and Si for two surfaces, respectively, whereas the second type cleavage has the same termination on both surfaces that consists of SiO. The water molecules were found to be decomposed and spontaneously form silanol group on both silica surfaces. After 4.0 ps, the chemical reactions were almost saturated. It was found that the silanol groups dominated on both surfaces. For the first type of cleavage, the final structure contains geminal, triple, and single silanols together with peroxy SiOOSi and SiOOH defects. For the second type of cleavage, the final structure contains geminal silanol, single silanol, and siloxane bridge. A small amount of unsaturated sites were also found on both surfaces. Further, we have shown that the newly formed rings at quartz surface range from four‐ to seven‐member ring for both surfaces. All the findings are in good consistent with the recent experimental observations and theoretical respects. © 2012 Wiley Periodicals, Inc.

Ab Initio Molecular Dynamics Study of Carbonation and Hydrolysis Reactions on Cleaved Quartz (001) Surface

“…from the ab initio MD simulations within the first 5 ps. It is expected that the reactive cleaved SiO 2 surface can be hydroxylated via hydrolysis reaction as reported by Ledyastuti et al 33 and Goumans et al 34 As shown in Figure 8 Figure 9 illustrates the detailed features regarding formation of HCO 3 configuration during hydrolysis reactions by using ELF. In Figure 9a, The charge transfer during the formation process of HCO 3 configuration on the basis of Bader analysis is shown in Figure 10.…”

“…In general, hydrolysis reaction occurs prior to carbonation reaction in the natural environment. However, according to previous works, 19,33 nonbridging O sites indeed can exist after hydrolysis reaction. In this paper, we studied carbonation at first.…”

“…Based on these results, it can be postulated that CO 3 2– and HCO 3 – in the formation water do not necessarily originate from dissociation of H 2 CO 3 . Active undercoordinated Si and nonbridging O atoms located on the cleaved SiO 2 surface are of great importance for formation of these CO 3 and HCO 3 configurations, which are usually protected by either cations or hydrogen bonding in the natural environment. , If we can successfully dissolve these cations into formation water or dehydrogenate the SiO 2 surface, CO 2 mineralization can be accelerated in the presence of Ca 2+ , Mg 2+ , or Fe 2+ , such as in basaltic rocks. Similar reactions may occur when CO 2 is used as the fracturing fluid in shale gas development .…”

“…There are mainly two relevant types of SiO 2 surfaces consisting of cleaved surface and reconstructed surface. , Generally, the former one is more reactive than the latter as it has dangling bonds on the surface, resulting in relatively high surface energy . Carbonation and hydrolysis reactions are two fundamental processes of CO 2 mineralization; extensive investigations have been done regarding chemical interactions among CO 2 , H 2 O, and SiO 2 systems, − which are essential parts for these processes. For interactions between SiO 2 and H 2 O, Ledyastuti et al and Goumans et al reported that hydroxyls from dissociation of H 2 O molecules can lead to formation of silanol groups on the cleaved SiO 2 surface by first-principles methods.…”

“…This surface structure is similar to those in previous studies. [33][34][35]40 It has nonbridging O atoms on the surface as shown in Figure S2. A bulk system with 300 CO 2 molecules was equilibrated initially by classical MD simulations under 323 K and 9 MPa with an isothermal-isobaric (NPT) ensemble by GROMACS version 4.5.5.…”