van der Waals interactions of the benzene dimer: towards treatment of polycyclic aromatic hydrocarbon dimers

TL;DR

This paper develops a modified density functional approach to accurately describe van der Waals interactions in planar molecules, demonstrated on benzene dimers, with implications for larger polycyclic aromatic hydrocarbons.

Contribution

A modified density functional is proposed to better capture van der Waals interactions in planar molecules, extending previous methods to larger aromatic systems.

Findings

Accurate binding distances for benzene dimers

Reliable binding energies for benzene dimers

Potential application to polycyclic aromatic hydrocarbons

Abstract

Although density functional theory (DFT) in principle includes even long-range interactions, standard implementations employ local or semi-local approximations of the interaction energy and fail at describing the van der Waals interactions. We show how to modify a recent density functional that includes van der Waals interactions in planar systems [Phys. Rev. Lett. 91, 126402 (2003)] to also give an approximate interaction description of planar molecules. As a test case we use this modified functional to calculate the binding distance and energy for benzene dimers, with the perspective of treating also larger, flat molecules, such as the polycyclic aromatic hydrocarbons (PAH).