# Effects of van der Waals Interaction on N2 Adsorption on Carbon Nanotubes: Proposal for New Force Field Parameters

## TL;DR

This paper shows that using the Lorentz–Berthelot combining rules leads to inaccurate predictions of nitrogen gas adsorption on carbon nanotubes, and proposes a better force field based on DFT calculations.

## Contribution

A new Lennard–Jones potential parametrized with DFT and van der Waals interactions for improved accuracy in simulating N2 adsorption on carbon nanomaterials.

## Key findings

- Lorentz–Berthelot underestimates interaction energies between N2 and carbon nanostructures.
- The proposed DFT-based potential shows good agreement with ab initio calculations.
- LB predicts lower nitrogen gas density in carbon nanotubes compared to the new potential.

## Abstract

The separation of carbon dioxide (CO2) from
nitrogen
gas (N2) in flue gas has become an emerging strategy to
mitigate climate change. Molecular simulations are valuable to provide
insights for the gas separation process. A careful choice of force
fields is required to avoid unrealistic predictions of thermodynamic
properties. Most studies use Lorentz–Berthelot combining rules
(LB) to obtain the interaction between different species. In this
context, we verified how accurate LB is in describing the interaction
of N2 molecules and carbon nanostructures by comparing
the interaction energies of LB with those from density functional
theory (DFT) calculations. Carbon nanomaterials were selected because
they are considered promising materials to perform N2/CO2 separation. The results show that the LB underestimates the
interaction energies and affects the prediction of the fundamental
properties of solid–fluid interfacial interactions. To overcome
this, we parametrized a Lennard–Jones potential using DFT and
considering van der Waals interactions. The proposed potential shows
good transferability and agreement with ab initio calculations. Molecular
simulations were performed to verify the effects of employing LB in
predicting the amount of nitrogen gas adsorbed in carbon nanotubes
(CNTs). LB predicts a lower density within them. Our results suggest
that LB leads to different adsorption properties.