Abstract

An investigation into the local environment of three metaphosphate glasses using molecular dynamics simulations is presented. The short rage structure of the phosphate and metal networks were determined from pair, cumulative and bond angle distribution functions as well as identifying the types of oxygen ions found within the networks. The short range structure was validated by comparing the results obtained from the simulations to structural properties determined experimentally and found in the literature. The phosphate network was found to consist of long linear chains of PO$\sb4$ tetrahedral units. This type of structure exists in the three metaphosphate glasses, indicating that the modifier has little effect on the structure of the phosphate backbone. A study of the metal networks revealed that the modifier's field strength plays a significant role in determining the short range order of the metal ions. Results indicate that the lead network has the highest degree of disorder since the lead ion occupies several different local environments compared to the local environments of the magnesium or zinc ions. Finally, a three body Born-Mayer-Huggins potential model was used to simulate the structure of P$\sb2$O$\sb5.$ This was achieved by developing the pair potential parameters for the P-O and P-P pair and comparing the structure of the simulated crystal to that of the static P$\sb2$O$\sb5$ crystal. The P$\sb2$O$\sb5$ glass was simulated using both the two body potential model as well as the three body model with the developed potential parameters. Results indicate that the three body model improved the short range order of the phosphorus ions.