Molecular dynamics modelling of the structure of barium silicate glasses BaO–SiO2

• Molecular dynamics models of barium silicate glasses have been presented.
• The barium–oxygen bond length is 2.79 Å and the coordination number is 7.
• Previously proposed layered structures are not observed in 40BaO–60SiO2 glasses.

The addition of barium to silicate glasses is of interest for applications such as radiation or thermal shielding. The barium silicate system, xBaO–(100 − x)SiO2, has a glass forming region around x = 25–40. Phase separation occurs at the lower range of x and has been a focus of previous studies. However, there have been very few structural studies of barium silicate glasses using diffraction or modelling. Here new results are presented from molecular dynamics modelling of glasses with x = 25, 33.3, 40 and 50. The glass models have the expected silicate network and the short range order around Ba typically has BaO peak distance of 2.79 Å and coordination of approximately 7, which is not similar to the crystals with x ≤ 40. The x = 40 glass model does not show any evidence of layered structures with approximately 4.2 Å spacing which were previously hypothesised.