Zirconium tungstate, ZrW2O8, has attracted an enormous amount of attention in the condensed matter community since its large isotropic negative thermal expansion (NTE) behaviour was reported in 1996. When heated, its cubic lattice contracts at approximately a similar rate to the usual positive thermal expansion of “normal” materials.
The material is also unusual because it becomes softer, and eventually amorphous, under hydrostatic pressure. We showed that the mechanism associated with this crystal–amorphous transition is very similar to that associated with the ambient-pressure NTE dynamics. But the real beauty of our model is that there is an implicit “choice” in zirconium tungstate can decrease its volume. What emerges are a set of ice-like rules that govern the formation of a glassy phase. The underlying connectivity of the ambient phase is preserved in this phase, but there are new additional bonds that produce any number of different configurations.
This work has been interesting in suggesting a tangible link between crystalline and amorphous phases that has implications for the crystal–amorphous transitions exploited in e.g. DVD-RAM technology.