Atomistic computer simulations of water interactions and dissolution of inorganic glasses

Abstract

Computer simulations at the atomistic scale play an increasing important role in understanding the structure features, and the structure-property relationships of glass and amorphous materials. In this paper, we reviewed atomistic simulation methods ranging from first principles calculations and ab initio molecular dynamics (AIMD) simulations, to classical molecular dynamics (MD), and meso-scale kinetic Monte Carlo (KMC) simulations and their applications to study the reactions and interactions of inorganic glasses with water and the dissolution behaviors of inorganic glasses. Particularly, the use of these simulation methods in understanding the reaction mechanisms of water with oxide glasses, water-glass interfaces, hydrated porous silica gels formation, the structure and properties of multicomponent glasses, and microstructure evolution are reviewed. The advantages and disadvantageous of these simulation methods are discussed and the current challenges and future direction of atomistic simulations in glass dissolution presented.npj Materials Degradation (2017) 1:16 ; doi:10.1038/s41529-017-0017-yThe corrosion or degradation of glasses in aqueous solutions are critical in a number of engineering and technological processes ranging from microelectronic packaging, glass reaction chambers, and the immobilization of nuclear waste materials, as well as in healthcare and biomedical fields such as dissolution of inhaled glass fibers and bioactive glasses for biomedical applications. In particular, immobilizing radioactive waste in borosilicate glasses is widely accepted as a preferred method to treat nuclear waste materials generated from civilian and military sources. This process, also known as vitrification, is a critical component of the cycle of nuclear energy to combat global environmental and energy challenges. Researchers from around the world have extensively invested in understanding glass corrosion in an effort to predict the long-term stability and release rate radionuclides to the environment during nuclear waste storage. 1,2Various mechanisms for glass corrosion have been proposed and despite intensive experimental investigations with advanced characterization techniques results are unclear. It is generally accepted that the corrosion of glass consists of a set of complex processes including hydration, hydrolysis, and ion-exchange that are coupled during glass dissolution. The initial stage is interdiffusion of proton or hydronium ions from the solution with sodium or other alkali ions in the glass.3 This is followed by the hydrophilic attack of water on the Si-O-Si or Si-O-Al linkages that lead to hydroxylation of the silicate glass network. The remaining hydrolyzed glass skeleton then undergoes condensation and repolymerization to form the hydrated nanoporous silica rich gel layer which can be protective, decreasing dissolution to a residual rate. [4][5][6] The morphology of the gel layer, such as thickness, pore structure, and chemical composition, depends on the original glass composition and the pH...

Hydration and reaction mechanisms on sodium silicate glass surfaces from molecular dynamics simulations with reactive force fields

“…As a result, direct correlation to experimental reaction rates cannot be reliably extracted due to size and timescale limitations. In order to make direct comparison with experimental results of dissolution rates, combining MD simulations to generate glass structure with Monte Carlo simulations that extend to longer time scales might be necessary as we recently reported . The results could however be analyzed to examine the structural and compositional changes at the interface and their correlation to the overall reaction rates.…”

“…use of a reactive potential is critical for analyzing all the reactions and material transport inside the glass and solution. Recent improvements of reactive MD force fields have allowed for several advances in the modeling of silica‐water interactions . In one of the most recent studies of sodium silicate hydration with the ReaxFF, leaching of sodium into water and accumulation at the interface of the leached Na + ions was observed along with proton transport inside the glass in the first nanosecond of reaction.…”

“…Recent improvements of reactive MD force fields have allowed for several advances in the modeling of silica-water interactions. [33][34][35][36][37][38] In one of the most recent studies of sodium silicate hydration with the ReaxFF, 39 leaching of sodium into water and accumulation at the interface of the leached Na + ions was observed along with proton transport inside the glass in the first nanosecond of reaction. Another recent study with the same ReaxFF potential studied the continuation of these simulations for a longer time (3 ns) and for different temperatures.…”

A comparative review of the aqueous corrosion of glasses, crystalline ceramics, and metals

“…The multiscale nature of corrosion, where atomistic surface processes (which are difficult or impossible to identify by lab experiments) end up in macroscopic dissolution (which is accurately measurable), requires modeling and crossvalidation on all length scales, in which atomic level models 207 typically inform the meso and macroscopic scales. Commonalities in modeling of the different materials exist, especially on the most fundamental quantum mechanical and the most macroscopic rate theory scales, with opportunities for cross-fertilization, particularly at the intermediate mesoscale.…”

“…The expected development of more accurate potentials will open up the possibility to study reaction, diffusion, defect formation, and migration at the extended atomic scale for more materials. 207 Modeling at the intermediate length and times scale is most prominently represented by stochastic models based on cellular automata and Monte Carlo modeling, 222,223 which are especially appropriate to model pitting corrosion, 222 and gel layer microstructure evolution during glass corrosion, 224 but have been explored to a much lesser degree for ceramic corrosion.…”