Thermodynamic scaling of diffusion in supercooled Lennard-Jones liquids

TL;DR

This study demonstrates that diffusion in supercooled Lennard-Jones liquids scales uniquely with the combined variable rho^g/T, linking the scaling exponent to the steepness of the repulsive potential, advancing understanding of structural relaxation.

Contribution

It reveals a universal scaling law for diffusion in Lennard-Jones liquids and relates the scaling exponent to the potential's steepness, providing new insights into intermolecular interactions.

Findings

Diffusion coefficients scale with rho^g/T in Lennard-Jones liquids.

The scaling exponent g is specific to each material.

Approximate inverse power law forms of u(r) are discussed.

Abstract

The manner in which the intermolecular potential u(r) governs structural relaxation in liquids is a long standing problem in condensed matter physics. Herein we show that diffusion coefficients for simulated Lennard-Jones m-6 liquids (8<m<36) in normal and moderately supercooled states are a unique function of the variable rho^g/T, where rho is density and T is temperature. The scaling exponent g is a material specific constant whose magnitude is related to the steepness of the repulsive part of u(r), evaluated around the distance of closest approach between particles probed in the supercooled regime. Approximations of u(r) in terms of inverse power laws are also discussed.