Structural Similarities Between a Glass and Its Melt

It is suggested that the large expansion coefficient increase that occurs near T g , for mixed oxide glasses is related to cooperative thermal displacements involving polyanionic clusters in the liquid state. This is illustrated by the striking relation between melt isoexpansion coefficient contours and structure for these ternary oxide systems. It is also shown that the molar volume dependence on composition for a series of oxide glasses can be quite similar to that observed for their liquid state analogs. The adjusted melt partial molar volume models can be used to develop realistic glass models, suggesting structural similarities between an oxide glass and its corresponding high‐temperature melt. Recently acquired evidence for alkali borogermanate compositions indicates a shift toward the right for the GeO 6 ⇄GeO 4 equilibrium in GeO 2− rich melts at relatively high temperatures. Thus, an exact structural correlation between an oxide melt and its corresponding glass may, in some cases, be limited to temperatures below T g +Δ T (where ΔT ~300° to 400°C).