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

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 Ba-O peak distance of 2.79 angstrom 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 angstrom spacing which were previously hypothesised. (C) 2014 Elsevier B.V. All rights reserved.