B₂O₃/SiO₂ substitution effect on structure and properties of Na₂O–CaO–SrO–P₂O₅–SiO₂ bioactive glasses from molecular dynamics simulations

Abstract

The effect of B2O3/SiO2 substitution in SrO-containing 55S4.3 bioactive glasses on glass structure and properties, such as ionic diffusion and glass transition temperature, was investigated by combining experiments and molecular dynamics simulations with newly developed potentials. Both short-range (such as bond length and bond angle) and medium-range (such as polyhedral connection and ring size distribution) structures were determined as a function of glass composition. The simulation results were used to explain the experimental results for glass properties such as glass transition temperature and bioactivity. The fraction of bridging oxygen increased linearly with increasing B2O3 content, resulting in an increase in overall glass network connectivity. Ion diffusion behavior was found to be sensitive to changes in glass composition and the trend of the change with the level of substitution is also temperature dependent. The differential scanning calorimetry (DSC) results show a decrease in glass transition temperature (Tg) with increasing B2O3 content. This is explained by the increase in ion diffusion coefficient and decrease in ion diffusion energy barrier in glass melts, as suggested by high-temperature range (above Tg) ion diffusion calculations as B2O3/SiO2 substitution increases. In the low-temperature range (below Tg), the Ea for modifier ions increased with B2O3/SiO2 substitution, which can be explained by the increase in glass network connectivity. Vibrational density of states (VDOS) were calculated and show spectral feature changes as a result of the substitution. The change in bioactivity with B2O3/SiO2 substitution is discussed with the change in pH value and release of boric acid into the solution.

Development of boron oxide potentials for computer simulations of multicomponent oxide glasses

“…The simulated structures are found to be in good agreement with the experimental data. These applications together with our other recent work further validate that the new parameters are compatible with previous published parameters for other elements of the modified Teter parameterization.…”

“…Addition of boron can also enhance bone repair and soft tissue healing. Due to the complex composition of bioactive glasses, molecular dynamics simulations have been used to extract the structural features of boron oxide‐containing bioactive glasses to correlate the structure, dynamics, and bioactivity behaviors of these novel bioactive glasses …”

Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass, part II: Structure

“…With recent developments of potential parameters for B-O pairs together with earlier parameters for aluminosilicate glasses, 38,39 atomistic structural models of multicomponent borosilicate glasses can now be generated. 26,27,[40][41][42][43][44][45] These potential models include the composition-dependent partial charge pairwise potential, 38,39 a polarizable shell-model potential, 46 and an empirical interatomic potential. 47 In recent studies, the atomic-level structure model of ISG was successfully generated using partial charge potential with the composition-dependent potential parameters for B, 26,48 with excellent agreement to results of high energy X-ray diffraction, NMR, and extended X-ray adsorption fine structure (EXAFS) experiments.…”

“…However, the limited availability of effective and transferable empirical potentials was the main hurdle in simulations of multicomponent borosilicate glasses. With recent developments of potential parameters for B‐O pairs together with earlier parameters for aluminosilicate glasses, 38,39 atomistic structural models of multicomponent borosilicate glasses can now be generated 26,27,40‐45 . These potential models include the composition‐dependent partial charge pairwise potential, 38,39 a polarizable shell‐model potential, 46 and an empirical interatomic potential 47 .…”

Effect of B2O3 on the structural and in vitro biological assessment of mesoporous bioactive glass nanospheres

“…33 Furthermore, both MD simulations and experimental efforts reported relevant structural information around glass network that boron did not form a complete regular tetrahedral structure like silicon. 34,36 The results also showed that the structural units of the borate glass network included not only [BO 3 ] trihedrons but also [BO 4 ] tetrahedrons. It is well known that [BO 3 ] units are considered to reduce chemical durability and therefore make the dissolution rate faster.…”