We propose a dynamic structure of coupled dynamic molecular strings for supercooled small polar molecule liquids and accordingly we obtain the Hamiltonian of the rotational degrees of freedom of the system.From the Hamiltonian,the strongly correlated supercooled polar liquid state is renormalized to a normal superdipole liquid state.This scenario describes the following main features of the primary or alpha-relaxation dynamics in supercooled polar liquids:(1) the average relaxation time evolves from a high temperature Arrhenius to a low temperature non-Arrhenius or super-Arrhenius behavior;(2) the relaxation function crosses over from the high temperature exponential to low temperature nonexponential form;and (3) the temperature dependence of the relaxation strength shows non-Curie features.According to the present model,the crossover phenomena of the first two characteristics arise from the transition between the superdipole gas and the superdipole liquid.The model predictions are quantitatively compared with the experimental results of glycerol,a typical glass former.
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