2007 Volume 47 Issue 5 Pages 643-647
The structure of CaO–CaF2–Al2O3–SiO2 systems with various F/O ratios has been investigated by using molecular dynamics simulation to evaluate the effect of F ions on the polymerization of melts. F ions in the melt are found to be mainly coordinated to Ca ions but not to Al ions. The formation of loosely bonded Ca–2F complexes in the CaO–CaF2–Al2O3–SiO2 melts is confirmed since the cumulative coordination number for F around the Ca ion at around the equilibrated bond length is approximately 2. Due to the formation of Ca–2F complexes, Ca ions available to the network modifier are decreased so that the degree of the polymerization of Si units in CaO–CaF2–Al2O3–SiO2 system is increased. The amount of aluminate tetrahedra embedded in silicate three-dimensional network unit is gradually decreased by the substitution of F ions for O ions because the amount of the silicate three-dimensional network unit is increased due to the decrease of Ca ions available to the network modifier.