Modelling of potentials for interparticle interactions between methanol molecules

TL;DR

This paper models the interparticle potentials between methanol molecules in vapor, combining electrostatic, dispersive, and repulsive forces, and compares the results with the OPLS potential to improve understanding of molecular interactions.

Contribution

It introduces a detailed multipole-based potential model for methanol interactions and fits parameters using experimental data, providing a more precise alternative to existing potentials.

Findings

Repulsive potential exponent n=28

Multipole moments match experimental and quantum calculations

Comparison shows differences with OPLS potential

Abstract

Peculiarities of interparticle interactions between methanol molecules in the methanol vapor are investigated. The bare potential is considered as a sum of repulsive, dispersive and electrostatic forces. It is supposed that H-bond is of electrostatic nature (the irreducible contribution caused by overlapping of electronic shells is unessential). The dispersive interaction is approximated with London's formula, the electrostatic interaction is modelled by a multipole expansion up to dipole-octupole contribution. The multipole moments are assumed to be equal to their experimental values or to quantum chemical calculations. The repulsion is modelled by power potential, whose parameters are fitted to the second virial coefficient and to the parameters of dimers. Along with the bare potential, the averaged potential of interparticle interaction is analyzed. It is shown that the repulsive potential has an exponent $n=28$. The multipole potential, presented in this paper, is scrupulously compared with the potential known as the OPLS.