Radial distribution and its spherical harmonics expansion in liquid CO2 at 250 K and 50 bar based on pressure-constant Monte Carlo simulation using Kihara Potential Model

TL;DR

This study computes the radial distribution function and spherical harmonics expansion coefficients of liquid CO2 at 250 K and 50 bar using pressure-constant Monte Carlo simulations with a Kihara potential, revealing detailed structural and orientational correlations.

Contribution

It extends previous work by calculating a comprehensive set of spherical harmonics expansion coefficients for liquid CO2, capturing detailed angular correlations up to l=8.

Findings

Radial distribution function shows peaks at 4.05 Å and 7.85 Å.

Expansion coefficients exhibit significant structures below 7.5 Å.

Molecular orientations tend to align along a preferred direction.

Abstract

The purpose of this article is to compute the radial distribution function of liquid CO2 at 250 K and 50 bar and its expansion coefficients by spherical harmonics as a function of intermolecular distance up to 20 angstroms for all possible combinations of angular indices l, l prime, and m less than or equal to 8, in contrast to past works of limited combinations. The positions and orientations of CO2 molecules were determined by pressure-constant Monte Carlo simulation using a Kihara potential model. It was found that the radial distribution function had an intense peak at 4.05 angstroms and a broad band at around 7.85 angstroms. The expansion coefficients had prominent structures below approximately 7.5 angstroms, showing positive and/or negative peaks, which indicated that the orientational correlations of the central molecule were intense with the molecules present in that region. It was also found that the peaks of some expansion coefficients were not small even when l = 8. Furthermore, molecular orientations had a tendency to orient along one direction presumably because of the linear form of CO2 molecule.