Composition Dependence of the Atomic Structures and Properties of Sodium Aluminosilicate Glasses: Molecular Dynamics Simulations with Reactive and Nonreactive Potentials

Abstract

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.

Composition Effect on Interfacial Reactions of Sodium Aluminosilicate Glasses in Aqueous Solution

“…Similar trends were observed for our NAS bulk glass compositions where network-modifying cations significantly affect the BO and NBO environments (Figure S7). As discussed in our previous work, the NBO fraction of bulk NAS bulk glasses decreases with increasing polymerizations where Al–O–Si and Al–O–Al linkages were formed with increasing Al 2 O 3 . On the other hand, Si–O–Si linkages noticeably reduce with increasing Al/Na ratio, further confirming the observations of NMR studies by Lee and Stebbins …”

“…This strategy is commonly used because partial charge rigid ion potential, although non-reactive, can effectively generate glass structures with few coordination defects, while direct generation of glass structure from ReaxFF has been shown to generate a noticeable amount of coordination defects during the cooling as has been shown by us earlier using sodium silicate glass as an example . The DCRP used in this work, however, can be used to generate glass structure with similar quality and low coordination defects as compared to the partial charge rigid ion potentials . As a result, for this work, all the glass structures were generated from DCRP.…”

“…48 We have also investigated the effectiveness of The Journal of Physical Chemistry B the DCRP in simulating the bulk structure of NAS glasses. 49,50 The studies showed that DCRP is capable of generating the atomic structures of NAS glasses with high accuracy by comparing them with experiments. Additionally, DCRP demonstrated a higher computational efficiency than ReaxFF.…”

“…Mahadevan and Du recently extended the other framework of reactive MD simulations using the diffuse charge reactive potential (DCRP) for simulating sodium silicate glasses. , Then, the DCRP was applied to study the hydration and surface reaction mechanisms as a function of the glass composition . We have also investigated the effectiveness of the DCRP in simulating the bulk structure of NAS glasses. , The studies showed that DCRP is capable of generating the atomic structures of NAS glasses with high accuracy by comparing them with experiments. Additionally, DCRP demonstrated a higher computational efficiency than ReaxFF.…”

Effect of Al2O3 addition on the thermal expansion of sodium alkaline‐earth silicate glasses: A molecular dynamics study

“…Note that the slower quenching at 0.2 K/ps of cooling rate provided the denser structures, which resulted in larger overestimation of density; however, the difference is insignificant. The FMP was more accurate than the Teter potential, which is widely used for modeling oxide glasses, 17,19,20,33,43,44 when evaluating the density with an NPT ensemble.…”