With the rapid iteration of smart displays, especially smartphones, cover plate glass as one of the key materials has made recent progress, becoming an important component in the field of electronic information display applications. Aluminosilicate glass with its unique properties (i.e., good impact resistance, scratch resistance, and high hardness, as well as excellent chemical and thermal stability) is an ideal candidate material for plate cover glass. There is relatively in-depth research on the influence of composition changes in aluminosilicate glass on its structure and properties, but most of the existing research focuses on the short-range structure (<5 Å) of the aluminosilicate glass network structure, while there is less research on its medium-range structure (5-20 Å). In this work, the influence of multi-layer network structure of aluminosilicate glass on its properties was investigated by molecular dynamics simulation and experiments.

The relationship between the composition-structure-properties of glass was investigated by experimental methods and molecular dynamics simulations. The glass samples were prepared by a conventional high-temperature melting method. The raw materials were weighed and mixed uniformly according to the molar ratio of oxides, put into a platinum-rhodium crucible (90% Pt and 10% Rh), and then heated in a high-temperature lifting furnace at 1640 ℃ for 2 h. After melting, the crucible containing the molten glass was removed and poured onto a preheated copper mold. Once it solidified, it was transferred to an annealing furnace, followed by natural cooling to room temperature to eliminate internal stresses in the glass, resulting in uniform, transparent bulk glass. The glass was then cut and mechanically polished to obtain the samples with various sizes.

The glass samples were simulated, and the simulated structure was a cubic box composed of approximately 10000 atoms. The initial dimensions of the simulation box were calculated based on predicted density and atomic mass. The initial structure was optimized by a soft potential to ensure structural integrity and prevent atomic loss. The potential function used was the Buckingham potential, and the Ewald summation method was used to handle long-range Coulomb interactions. The cutoff radius was set to 10 Å, with an integration time step of 0.001 ps. The initial structure was randomly generated by an open-source software named ATOMSK.

The statistical results of the short-range structural characteristics of silicate glass indicate that there are no significant changes in the position and intensity of the O—O peak, and the intensity of the Al—O peak near 1.7 Å gradually increases as Al₂O₃ content increases. The number of Al—O structural units in the glass network structure increases, having a clear symmetrical distribution with aluminum primarily in a four-coordinate environment. The strength of the Si—O bond decreases with the reduction of SiO₂. The number of [SiO₄] tetrahedral groups decreases, and some alkaline earth metal ions in the glass network structure transform into ions that serve to compensate for the charge of the [AlO₄] tetrahedral groups.

The statistical analysis of the medium-range structural characteristics of aluminosilicate glass indicates that as Al₂O₃ content increases, the Q value of the first sharp diffraction peak (FSDP) shifts towards higher values, the ring size distribution shows a certain sharpening degree with the decreasing proportions of small rings (i.e., 3-membered and 4-membered rings) and large rings (i.e., ≥7-membered rings), while increasing the proportions of medium-sized rings (i.e., 5-membered and 6-membered rings). The smaller rings, such as the three-membered and four-membered rings, typically possess a higher energy and are more prone to structural rearrangement or breakage, whereas the larger rings, such as the five-membered and six-membered rings, are relatively stable. This indicates a reduction in the medium-range disorder of the glass network structure, resulting in a denser network structure.

The mechanical properties of the glass (i.e., density, elastic modulus, and Vickers hardness) gradually increase with the increase of Al₂O₃ content. The mechanical characteristics of the glass are positively correlated to the density of its network structure. The increase in the content of the [AlO₄] network structure makes the network structure denser, while the combined effect of [AlO₄] and [SiO₄] gradually enhances the integrity of the glass network. This results in a decrease in the average coefficient of thermal expansion, an increase in the strain point and softening point, and an increase in high-temperature viscosity.

The relationship between the composition-structure-properties of aluminosilicate glass was elucidated through experiments and molecular dynamics simulations. The substitution of Al³⁺ for Si⁴⁺ induced changes in the short-range and medium-range network structures of the glass, leading to an increase in the bridging oxygen content and a sharpening of the ring size distribution. The structural factor could shift towards higher values at the position of the first sharp diffraction peak (FSDP), resulting in an increase in the order of the short-range and medium-range network structures, and making the network structure denser. Consequently, the density, elastic modulus, Vickers hardness, strain point, softening point, and viscosity of the glass melt all increased, while the average coefficient of thermal expansion decreased.