Medium-range topological constraints in binary phosphate glasses

The theory of temperature-dependent topological constraints has been used to successfully explain the compositional dependence of glass properties for oxide and non-oxide compositions. However, even though the predictions are qualitatively accurate, not all quantitative predictions are as precise. Here, we report on the applications of this theoretical framework to available data for binary phosphate and silver metaphosphate--silver halide glasses. We find that some compositions are overconstrained and some are underconstrained relative to the predicted values. We suggest that the origin of this difference is due to the presence of medium-range constraints such as sterical hindrance which is dependent on packing density and chain length.