A Study on the Structures of (62-x)CaO center dot 38Al(2)O(3)center dot xBaO Glasses by Molecular Dynamics Simulation

Molecular dynamics simulation (MD) of (62-x)CaO center dot 38Al(2)O(3)center dot xBaO glasses has been carried out using empirical potentials with the covalent term. The simulations closely reproduce the total neutron correlation functions of glass with 5 mol% BaO and physical properties of these glasses such as elastic constants. For these glasses, aluminum is tetrahedrally coordinated by oxygen, but there is a part of fivefold and six-fold coordination of aluminum. There are no major changes to the mid-range structure of glass, as barium is substituted for calcium. To predict the barium coordination number, we have used the bond valence (BV) theory and also compared the results of simulation with Bond valence. The coordination number for oxygen around barium atoms is close to 8 and the average distance of barium and oxygen is nearly 2.80 angstrom. The viscosity of these glasses increases with the content of barium oxide substituted for calcium oxide.