Molecular dynamics study of the structure and properties of noncrystalline B2O3-CaO oxides

Molecular dynamics simulations with Born-Mayer pair potentials were used to study B2O3-CaO oxides at 2000 M. In each simulation, the system included about 500 ions in a cubic central box with periodic boundary conditions. The thermodynamic, structural, and topological properties of the system were calculated. According to simulation results, all of the oxides have a loose structure, which becomes progressively looser with increasing B2O3 concentration. In CaO-rich oxides, the boron ions are in tetrahedral coordination, which gives way to trigonal coordination as the B2O3 content rises to above 50 mol %. The structure is fully polymerized at B2O3 concentrations above 20 mol %. The self-diffusion coefficients are very low, below 10(-6) cm(2)/s, as is the electrical conductivity of B2O3, which could not be estimated by molecular dynamics simulations.