Elastic Moduli and Stress Relaxation Times in Liquid Argon

Abstract

The elastic shear and bulk moduli of liquid argon have been calculated for values of temperature and density along the saturation boundary. The temperature range was from 83.8–101.8°K and the density range from 1.414 to 1.300 g/cm3. The calculations were performed by allowing the array of atoms of the Bernal–Scott liquid model to interact with a Lennard-Jones pair potential function and studying the changes in energy of this array as a function of homogeneous strain. The density was varied by random removal of atoms from the array. Both the shear and bulk moduli decrease steeply with decreasing density as is observed in molecular liquids. The shear- and volume-stress relaxation times were calculated on the assumption of a single Maxwell relaxation mechanism. The average shear relaxation time τs = 2.22 × 10−13sec, and the average volume relaxation time τυ = 2.54 × 10−13sec. The relaxation times are practically independent of temperature in liquid argon under its saturated vapor pressure in the region of the triple point.