Structure Of Sodium Silicate Glasses Research Articles

New insights into the structure of sodium silicate glasses by force-enhanced atomic refinement

Atomistic simulations can offer direct access to the atomic structure of glasses, which is otherwise invisible from conventional experiments. However, molecular dynamics (MD) simulations of glasses based on the melt-quenching technique remain plagued by the use of high cooling rates, while reverse Monte Carlo (RMC) modeling can yield non-unique solutions. Here, we adopt the force-enhanced atomic refinement (FEAR) method to overcome these limitations and decipher the atomic structure of a sodium silicate glass. We show that FEAR offers an unprecedented description of the atomic structure of sodium silicate, wherein the simulated configuration simultaneously exhibits enhanced agreement with experimental diffraction data and higher energetic stability as compared to those generated by MD or RMC. This result allows us to reveal new insights into the atomic structure of sodium silicate glasses. Specifically, we show that sodium silicate glasses exhibit a more ordered medium-range order structure than previously suggested by MD simulations. These results pave the way toward an increased ability to accurately describe the atomic structure of glasses.

Effect of Sodium Oxide Modifier on Structural and Elastic Properties of Silicate Glass.

Molecular dynamics (MD) simulations and Brillouin light scattering (BLS) spectroscopy experiments have been carried to study the structure of sodium silicate glasses (SiO2)(100-X)(Na2O)X, where X ranges from 0 to 45 at room temperature. The MD-obtained glass structures have been subjected to energy minimization at zero temperature to extract the elastic constants also obtained by BLS spectroscopy. The structures obtained are in good agreement with the structural experimental data realized by different techniques. The simulations show that the values of the elastic constants as a function of X (i.e., Na2O mol %) agree well with those measured by BLS spectroscopy. The variations of elastic constants C11 and C44 as a function of Na2O mol % are discussed and correlated to structural results and potential energies of oxygen atoms.

分子動力学法を用いたナトリウムケイ酸塩ガラスの修飾イオンとネットワーク構造の関係

Network structure of sodium silicate glasses was investigated by molecular dynamics simulation. The simulations were performed that determined using the first-principles calculation. Variation of SiO4 units and bond angles for alkali content were consistent with experimental results. It was also suggested that sodium ion and calcium ion give different effect to glass structure each other.

Structural study of sodium silicate glasses and melts

We report an X-ray diffraction study and modeling of the structure of sodium silicate glasses and melts that are used as binders in the production of the latest generation of ceramic welding fluxes. Experimental data and reverse Monte Carlo (RMC) simulations results are analyzed in comparison with results for a sodium silicate monolith and the water glass prepared from it. The RMC results agree well with structure factor and radial distribution function analysis data. The sodium silicate glasses and melts are shown to have a number of structural features, which have much in common with their crystalline counterparts. The high capacity of the silicate glasses and melts for water is due to the presence of nanopores formed (largely) by six-membered rings of silicon-oxygen tetrahedra and partially by sodium-oxygen octahedra.

Silver clustering in sodium silicate glasses: a molecular dynamics study

Molecular dynamics (MD) computer simulations with empirical potentials are applied to model the structure of sodium silicate glasses and the mobility of metallic particles enclosed. The particles are assumed to be generated by the Na–Ag ion-exchange, reducing the Ag ions and subsequent annealing. The theoretical investigations consider the modification of the glass structure owing to the ion exchange as well as the migration and clustering of the silver particles. Moreover, from the study of the migration processes we refine the empirical potentials applied to MD simulations and subsequent high resolution electron microscope (HREM) image calculations.

Correlation between dielectric constant and chemical structure of sodium silicate glasses

The chemical structure of sodium aluminosilicate glasses is determined by high resolution x-ray photoelectron spectroscopy (XPS) as silicon is gradually replaced by aluminum. A well-defined chemical state is found for silicon, aluminum, and sodium atoms, while three different environments are identified for oxygen atoms corresponding to Si–O–Si, Si–O–Al, and Si–O–Na bonds. The binding energy of Na 1s photoelectrons increases significantly with increasing aluminum substitution while that of Al 2p and components of O 1s photoelectrons remains approximately constant. Thus, the ionicity of sodium increases with aluminum amount, but the over all electron density around silicon, aluminum, and different types of oxygen atoms remains unchanged. The dielectric constant of the glasses increases with increasing aluminum substitution. It is analyzed in terms of the polarizabilities of constituent structural units, viz., silicon tetrahedra, nonbridging oxygen–sodium ion pairs, and aluminum tetrahedron–sodium ion pairs. The electronic polarizability of oxygen ions depends linearly on their negative charge and can be correlated to the O 1s XPS binding energy. The ionic polarizability of sodium ions increases with an increasing aluminum amount, and correlates directly with the Na 1s XPS binding energy.

Effect of Small Concentrations of Gallium Oxide on the Structure of Sodium Silicate Glasses

The glass transformation temperatures and de electrical conductivities of sodium silicate glasses with low‐level gallia additions have been measured. The composition/property relationships observed in these glasses are different from those observed with larger gallia additions. These trends are discussed in terms of structural models proposed for these glasses.

Structure of Glasses and Melts in the Na<sub>2</sub>O-SiO<sub>2</sub>-TiO<sub>2</sub> System

In order to elucidate the influence of TiO2 on the structure of sodium silicate glasses and melts, a MD (molecular dynamics) simulation using the ionic pair potential function, Born-Mayer-Huggins form, has been performed for 0.25Na2O⋅0.47SiO2⋅0.28TiO2 glass and the corresponding melt. The calculation pair correlation functions were in good agreement with a RDF (radial distribution function) curve obtained from the previous structural analysis by TOF (time-of-flight) pulsed neutron scattering. The computer-simulated configuration for the glass indicated that most of Ti ions were in 4-fold coordination, whilst the remainder were 6-fold coordination. The frequency spectrum of the glass obtained from MD simulation was in good agreement with the Raman spectra measured on glasses in the Na2O-SiO2-TiO2 system. As a result, the weak Raman band near 700cm-1 can be assigned to Ti ion in 6-fold coordination, and the strong Raman band near 900cm-1 reflects a Ti-O stretching band, which is characteristic of TiO4 tetrahedra corner-linked with SiO4 tetrahedra. The Raman spectra for glasses and melts in Na2O-SiO2-TiO2 system were measured by the high temperature Raman spectroscopic technique. A slight difference in the obtained Raman spectra was observed between the glasses and the corresponding melts, implying that the structure of glass should be similar to that of the corresponding melt.

A molecular dynamic calculation of the structure of sodium silicate glasses

Molecular dynamic calculations of the structure of a series of sodium silicate glasses, a common soda–lime glass, a sodium borosilicate glass and a sodium–potassium silicate glass were made. Calculated radial distribution functions are in good agreement with existing x-ray diffraction data and a previous MD calculation on silica glass. During the dynamical runs alkali and alkaline earth cations cluster around nonbridging oxygen atoms. In the borosilicate glass studied, the boron atoms enter the silica network and are tetrahedrally coordinated by oxygen. Other features of the simulated glasses include the coordination number of cations, the degree of inhomogeneity, the distribution of bridging and nonbridging oxygen atoms, the Si–O–Si bond angles, the ring structure, etc. Some preliminary diffusion studies will be presented.

The Structure of Sodium Silicate Glasses and Their Far-Infrared Absorption Spectra1

The Structure of Sodium Silicate Glasses and Their Far-Infrared Absorption Spectra¹

Relationship between the infrared reflection spectra and structure of sodium silicate glasses

Relationship between the infrared reflection spectra and structure of sodium silicate glasses