Diffusivity, a measure for how rapidly a fluid self-mixes, shows an intimate,but seemingly fragmented, connection to thermodynamics. On one hand, the"configurational" contribution to entropy (related to the number ofmechanically-stable configurations that fluid molecules can adopt) has longbeen considered key for predicting supercooled liquid dynamics near the glasstransition. On the other hand, the excess entropy (relative to ideal gas)provides a robust scaling for the diffusivity of fluids above the freezingpoint. Here we provide, to our knowledge, the first evidence that excessentropy also captures how supercooling a fluid modifies its diffusivity,suggesting that dynamics, from ideal gas to glass, is related to a single,standard thermodynamic quantity.
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