Ab Initio Modeling of Structure and Properties of Single and Mixed Alkali Silicate Glasses

Abstract

A density functional theory (DFT)-based ab initio molecular dynamics (AIMD) has been applied to simulate models of single and mixed alkali silicate glasses with two different molar concentrations of alkali oxides. The structural environments and spatial distributions of alkali ions in the 10 simulated models with 20% and 30% of Li, Na, K and equal proportions of Li-Na and Na-K are studied in detail for subtle variations among the models. Quantum mechanical calculations of electronic structures, interatomic bonding, and mechanical and optical properties are carried out for each of the models, and the results are compared with available experimental observation and other simulations. The calculated results are in good agreement with the experimental data. We have used the novel concept of using the total bond order density (TBOD), a quantum mechanical metric, to characterize internal cohesion in these glass models. The mixed alkali effect (MAE) is visible in the bulk mechanical properties but not obvious in other physical properties studied in this paper. We show that Li doping deviates from expected trend due to the much stronger Li-O bonding than those of Na and K doping. The approach used in this study is in contrast with current studies in alkali-doped silicate glasses based only on geometric characterizations.

Synergistic adsorptions of Na2CO3and Na2SiO3on calcium minerals revealed by spectroscopic andab initiomolecular dynamics studies

“…NaSiO(OH) 3 ; and (3) the protonated form of the dimer, i.e. Si 2 O(OH) 6 . The Si(OH) 4 molecule placed onto the carbonated (111) CaF 2 surface adsorbed establishing ve Na-O bonds with two Na-O bonds formed by two different oxygen atoms and one Na-O bond by the last oxygen atom (Fig.…”

“…With an estimated annual worldwide market value of 8.9 billion USD in 2017, 1 alkali silicate reagents are among the most used inorganic reagents worldwide. These environmentally friendly reagents have been intensively studied over past decades [2][3][4][5][6] since they commonly serve as a basis for the production of a large range of silica-containing materials. [7][8][9] Besides, their interesting properties lead to a wide range of industrial applications as additives, including detergents, foundries, adhesives, surface coatings, and water treatment.…”

Atomic-Scale Understanding of Structure and Properties of Complex Pyrophosphate Crystals by First-Principles Calculations

“…Mulliken analysis is more effective if a localized basis is used, and we always use the minimal basis as implemented in OLCAO method with the same atomic basis for all atomic species [27]. The same approach has been successfully applied to many different materials systems including complex biomolecular systems [35][36][37][38][39][40][41][42][43][44][45].…”

“…The combination of using VASP and OLCAO packages with two different basis expansions is highly effective in revealing the subtle features in the material properties especially on the atomic scale details. The method is particularly useful for highly complex crystals or non-crystalline materials as demonstrated in some of recent publications [35][36][37][38][39][40][41][42][43][44][45].…”

Understanding the atomistic origin of hydration effects in single and mixed bulk alkali‐silicate glasses

“…The main goal for this study was to provide details of the electronic structure and internal bonding and correlate them with mechanical and optical properties in seven carefully constructed bulk models of hydrous alkali‐silicate glasses including pure silica, single alkali doped (Li, Na, K) and mixed alkali doped (Li + Na, Li + K, and Na + K) in order to shed some light on the MAE and compare with the results from corresponding anhydrous models . It should be clearly stated that this work is restricted to bulk glasses so any comparison with results related to surfaces of the glass need to be carefully scrutinized.…”