Fragile-to-strong crossover in supercooled liquids remains elusive
Transport properties of glass-forming liquids change markedly around an onset temperature To. For temperatures T > To, these properties depend little on T, whereas for T Tx. However, Mallamace et al. (2) reported the observation of Tx for a large number of supercooled liquids. In truth, they observed the onset of supercooled behavior, and the reported values of Tx are poor lower-bound estimates of onset temperatures To. This fact is consistent with transport decoupling appearing only below temperatures identified with the crossover in ref. 2.