Equation of state and manifestation of non-spherical contribution of interaction potential in liquid rubidium metal

TL;DR

This paper develops a semi-empirical equation of state for liquid rubidium, demonstrating that a Lennard-Jones (8.5-4) potential model originally for cesium can be adapted, and analyzes non-spherical interaction contributions.

Contribution

It applies a Lennard-Jones (8.5-4) potential model to liquid rubidium and quantifies non-spherical interaction effects using multipole moments and virial coefficients.

Findings

Lennard-Jones (8.5-4) potential fits liquid rubidium data well.

Non-spherical interactions significantly influence the second virial coefficient.

Deviations occur at low temperatures, indicating model limitations.

Abstract

A semi-empirical equation of state is presented for the liquid rubidium metal. The Lennard-Jones (8.5-4) potential model, which originally has been derived for liquid cesium metal, is found to be suitable for modeling of liquid rubidium metal as well. By applying the experimental PVT data of compressed liquid metal in the range 500 K to 1600 K, the slope B, and intercept C, of the linear isotherms are determined and accordingly parameters of the potential function are calculated. The contribution of non-spherical part of the interaction potential to the second virial coefficient B2ns, is calculated by using the Boltzman factor that involves the proposed model potential. The multipole moments, standing as approximation of the non-spherical contribution by multipole expansion, are calculated by the Gaussian 98W program at the B3LYP level of theory. It can be concluded that the slope of the isotherm conforms to B2ns quite well, though some deviations at low T's exist.