COMPUTER-SIMULATION OF THE STRUCTURE OF LIQUID AND GLASSY CAO-P2O5 OXIDES

Molecular dynamics and continuous static relaxation simulations were u sed to develop ionic models of liquid (2000 K) and amorphous (0 K) CaO -P2O5 oxides. In each simulation, the system included about 500 ions i n a cubic box with periodic boundary conditions. The system was found to exhibit strongly hysteretic behavior. The density of model structur es and the P-O distance obtained in simulations agree well with experi ment. The volume change upon the formation of mixed oxides from consti tuent oxides is positive, while the energy change is negative. Most ph osphorus ions are in fivefold coordination, although fourfold and sixf old coordinations can also be met. The distributions of connected grou ps (polyanions) and minimum-length ring-shaped configurations are anal yzed. The (CaO)(x)(P2O5)(1-x) oxides with x less than or equal to 0.8 are shown to have a topologically loose structure.