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

Abstract

Abstract. We analyse the inverse reduced fluctuations (inverse ratio of relative volume fluctuation to its value in the hypothetical case where the substance acts an ideal gas for the same temperature-volume parameters) for simple liquids from experimental acoustic and thermophysical data along a coexistence line for both liquid and vapour phases. It has been determined that this quantity has a universal exponential character within the region close to the melting point. This behaviour satisfies the predictions of the meanfield (grand canonical ensemble) lattice fluid model and relates to the constant average structure of a fluid, i.e. redistribution of the free volume complementary to a number of vapour particles. The interconnection between experiment-based fluctuational parameters and self-diffusion characteristics is discussed. These results may suggest experimental methods for determination of self-diffusion and structural properties of real substances.

Isobaric Heat Capacity, Isothermal Compressibility and Fluctuational Properties of 1-Bromoalkanes

“…Such a behaviour is expectable. It has been detected before for simple liquids (liquid saturated noble gases [4]) and pure n-alkanes [21]. Besides, the high accuracy of the linear fit supports the conclusions about the accuracy of measurements.…”

Estimating the liquid properties of 1-alkanols from C5 to C12 by FT-EoS and CP-PC-SAFT: Simplicity versus complexity

“…The fluctuation theory approach [5][6][7][8] relates the microscopic density fluctuations with a macroscopic thermodynamic property, namely the isothermal compressibility κ T and temperature T as follows: …”

“…Equation 2 allows detecting a fundamental regularity taking place away from the critical points for various liquids having dissimilar densities [5][6][7][8], namely the following simple exponential function:…”

The speed of sound and the heat capacity of liquid neon in the subcritical region

“…The inverse ratio of the volume fluctuations in a condensed medium to its value for the hypothetical case of ideal gas at the same thermodynamic conditions [9] reads as follows…”

“…The recent study of the volume fluctuations in liquid noble gases and the corresponding coexisting vapours under saturation conditions [9] has detected a certain irregularity in the plot of fluctuations in liquid neon in the subcritical region. Thus, the main goal of this work is to explore in details the values of thermodynamic quantities (the speed of sound, the isobaric and isochoric heat capacities) provided by NIST Chemistry WebBook in the direct vicinity of the critical point and to discuss their more accurate approximations within this region.…”