Modelling the Onset of Phase Separation in CaO-SiO2-CaCl2 Chlorine-Containing Silicate Glasses

The addition of chlorine into a bioactive glass composition is expected to reduce its abrasiveness and increase its bioactivity which is important for dental applications such as toothpastes. There is a lack of information and understanding regarding the structural role of chlorine in chlorine-containing bioactive silicate glasses. This has prompted classical core-shell model molecular dynamics simulations of (50-x/2)CaO-(50-x/2)SiO2-xCaCl2 glasses to be performed, where x ranges from x=0.0 to x=43.1 mol% CaCl2. These ternary glasses are advantageous for a fundamental study because they do not have additional network former (e.g. phosphorus) or modifier (e.g. sodium) ions typically found in bioactive glass compositions. The (50-x/2)CaO-(50-x/2)SiO2-xCaCl2 glasses were seen to become phase separated around the x=16.1 mol% CaCl2 composition and chlorine predominantly coordinated with calcium. These findings provide a solid foundation for further computational modelling work on more complex chlorine-containing bioactive glass compositions.