Hard-wall Potential Function for Transport Properties of Alkali Metals Vapor

TL;DR

This paper introduces a hard-wall Lennard-Jones (15-6) potential model to accurately predict the transport properties of alkali metal vapors, validated against experimental data with high precision.

Contribution

It proposes a novel hybrid LJ(15-6) potential with a hard-wall repulsion to improve transport property predictions of alkali metal vapors.

Findings

Predicted viscosities agree within 3% of experimental data.

Predicted thermal conductivities match experiments within 3.6%.

LJ(15-6) hybrid potential outperforms other models in accuracy.

Abstract

This study demonstrates that the transport properties of alkali metals are determined principally by the repulsive wall of the pair interaction potential function. The (hard-wall) Lennard-Jones(15-6) effective pair potential function is used to calculate transport collision integrals. Accordingly, reduced collision integrals of K, Rb, and Cs metal vapors are obtained from Chapman-Enskog solution of the Boltzman equation. The law of corresponding states based on the experimental-transport reduced collision integral is used to verify the validity of a LJ(15-6) hybrid potential in describing the transport properties. LJ(8.5-4) potential function and a simple thermodynamic argument with the input PVT data of liquid metals provide the required molecular potential parameters. Values of the predicted viscosity of monatomic alkali metals vapor are in agreement with typical experimental data with the average absolute deviation 2.97% for K in the range 700-1500 K, 1.69% for Rb, and 1.75% for Cs in the range 700-2000 K. In the same way, the values of predicted thermal conductivity are in agreement with experiment within 2.78%, 3.25%, and 3.63% for K, Rb, and Cs, respectively. The LJ(15-6) hybrid potential with a hard-wall repulsion character conclusively predicts best transport properties of the three alkali metals vapor.