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重庆十分快乐现场开奖:Link between molecular mobility and order parameter during liquid–liquid transition of a molecular liquid
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Contrary to a common sense that a liquid state is unique for a pure system, there have been a number of indications for the presence of more than two liquid states. The transition between the liquid states is called “liquid–liquid transition.” There has so far been little information on how local molecular dynamics changes during the transformation. Here, we reveal the correlation between the order parameter and molecular dynamics by real-time dielectric spectroscopy measurements during the transformation from liquid I to liquid II in a molecular liquid, triphenyl phosphite. Our results suggest that the local order parameter controls local dynamics. Our finding sheds light on the nature of liquid–liquid transition from a perspective of molecular-level dynamics.
Liquid–liquid transition (LLT) is the transformation of one liquid to another via first-order phase transition. For example, LLT in a molecular liquid, triphenyl phosphite, is macroscopically the transformation from liquid I in a supercooled state to liquid II in a glassy state. Reflecting the transformation from the liquid to glassy state, the LLT is accompanied by considerable slowing down of overall molecular dynamics, but little is known about how this proceeds at a molecular level coupled with the evolution of the order parameter. We report such information by performing time-resolved simultaneous measurements of dielectric spectroscopy and phase contrast microscopy/Raman spectroscopy by using a dielectric cell with transparent electrodes. We find that the temporal change in molecular mobility crucially depends on whether LLT is nucleation growth type occurring in the metastable state or SD type occurring in the unstable state. Furthermore, our results suggest that the molecular mobility is controlled by the local order parameter: more specifically, the local activation energy of molecular rotation is controlled by the local fraction of locally favored structures formed in the liquid. Our study sheds light on the temporal change in the molecular dynamics during LLT and its link to the order parameter evolution.
- liquid–liquid transition
- phase ordering dynamics
- order parameter
- local molecular dynamics
- dielectric relaxation
?1Present address: Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan.
- ?2To whom correspondence should be addressed. Email: .
Author contributions: H.T. designed research; K.-i.M. performed research; K.-i.M. and H.T. analyzed data; and K.-i.M. and H.T. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1822016116/-/DCSupplemental.
Published under the PNAS license.