Entropy increase in the amorphous-to-crystalline phase transition in zirconium tungstate

It has been shown that zirconium tungstate (ZrW2O8) exhibits isotropic negative thermal expansion and undergoes pressure-induced amorphization above 1.5 GPa, at room temperature. Now, we have found that amorphous ZrW2O8 undergoes endothermic recrystallization, and thus have an overall entropy lower than that of the crystalline phase. This counterintuitive behavior can be rationalized owing to the same low-energy modes already shown to be responsible for the isotropic negative thermal expansion and the anomalously high heat capacity at low temperatures exhibited by ZrW2O8. Our findings point to an entire class of materials that should behave similarly to ZrW2O8 and constitute direct experimental evidence for an overall entropy increase in an amorphous-to-crystalline transition.