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Understanding the composition–structure–property relations of glass materials is essential for their technological applications. In this study, the structures and properties of a series of sodium aluminosilicate glasses with varying Al2O3/Na2O ratios ((35 – x)­Na2O–xAl2O3–65SiO2, x = 0, 5, 10, 15, 17.5, 20) covering peralkaline to peraluminous compositions, have been studied by using molecular dynamics simulations with two types of interatomic potentials: a fixed partial charge pairwise potential (Teter) and a reactive diffusive charge reactive potential (DCRP). The short and medium structural features such as bond lengths, coordination numbers, Qn distributions, and ring size distributions were obtained and compared with experimental data. It was found that silicon remained fourfold-coordinated throughout the compositional range, while a noticeable amount of fivefold-coordinated aluminum together with oxygen triclusters (TBO) are present in compositions with higher Al2O3 contents (R Al/Na > 1). In addition, the simulation results from both potentials show a certain level of violation of the Al avoidance rule by exhibiting a non-negligible amount of [AlO x ]–[AlO x ] polyhedral connections. Neutron and X-ray diffraction structure factors of the simulated glasses were calculated and compared with available experimental data. The mechanical properties, including Bulk, Shear, and Young’s modulus, were calculated and found to increase with increasing R Al/Na, in good agreement with the experiments. Correlations of the properties with glass structures as a function of glass compositions and the advantages as well as potential issues of the two sets of potentials in modeling sodium aluminosilicate glasses are discussed in the context of features of glass structures and the prospect of future simulations of glass–water reactions.

Understanding the underlying reaction mechanisms responsible for aluminosilicate glass dissolution in aqueous environments is crucial for designing glasses for technological applications ranging from architecture windows and touch screens to nuclear waste disposal. This study investigated the glass composition effect on the interfacial reactions of sodium aluminosilicate (NAS) glasses using molecular dynamics (MD) simulations with recently developed reactive potentials. Glass–water interfacial models of six NAS glasses with varying Al2O3/Na2O ratios were investigated for up to 4 nanoseconds (ns) to elucidate the interfacial reaction mechanisms at ambient temperature. The results showed that the coordination defects, such as undercoordinated Si and Al, as well as non-bridging oxygens (NBOs) accumulated at the glass surfaces, play a crucial role in the initial hydration reaction process of the glasses. They promote the formation of silanol (Si–OH) and aluminol (Al–OH) species together with the Na+ ⇔ H+ ion-exchange reactions. The z-density profiles of H2O and H+ ions affirmed the water/H+ propagation into the glass up to 2 nanometers after 4 ns reactions. The penetration depth depends on the composition and shows a nonlinear dependence, suggesting that the subsequent water penetration, particularly into the bulk glass, is supported by the availability of random channels. Aluminol formations, including Al–OH or Al–OH2 near the surface, were found to form mainly through the hydrolysis of Al–O–Al bonds and hydration of Al+–NBO– units. While water molecules are involved in initial interfacial reactions, water penetration into the bulk glass region is primarily achieved by proton transfer. Compared to highly mobile proton transfer involving silanol groups, proton transfer associated with [AlO4]− species is much more limited, particularly in the bulk glass region. These new insights into the role of aluminum in interfacial reactions of the NAS glasses can help to understand the initial dissolution mechanisms and in designing more durable glasses.

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