Limits of structure stability of simple liquids revealed by study of relative fluctuations

摘要

We analyse the inverse reduced fluctuations (inverse ratio of relative volumefluctuation to its value in the hypothetical case where the substance acts anideal gas for the same temperature-volume parameters) for simple liquids fromexperimental acoustic and thermophysical data along a coexistence line for bothliquid and vapour phases. It has been determined that this quantity has auniversal exponential character within the region close to the melting point.This behaviour satisfies the predictions of the mean-field (grand canonicalensemble) lattice fluid model and relates to the constant average structure ofa fluid, i.e. redistribution of the free volume complementary to a number ofvapour particles. The interconnection between experiment-based fluctuationalparameters and self-diffusion characteristics is discussed. These results maysuggest experimental methods for determination of self-diffusion and structuralproperties of real substances.