Role of Exchange in Density Functional Theory for Weakly-Interacting Systems: Quantum Monte Carlo Analysis of Electron Density and Interaction Energy

TL;DR

This study uses quantum Monte Carlo methods to evaluate how exchange functionals influence density functional theory's accuracy in describing weak interactions, revealing that electron densities are well-captured despite variations in binding energies.

Contribution

It provides a detailed analysis of the role of exchange in DFT for weakly-interacting systems using QMC, highlighting the importance of exchange energy density at large reduced density gradients.

Findings

DFT accurately describes electron density in weak interactions.

Binding energies vary significantly with exchange-correlation approximations.

Enhancement of exchange energy density at high reduced density gradients is crucial.

Abstract

We analyze the density functional theory (DFT) description of weak interactions by employing diffusion and reptation quantum Monte Carlo (QMC) calculations, for a set of benzene-molecule complexes. While the binding energies depend significantly on the exchange correlation approximation employed for DFT calculations, QMC calculations show that the electron density is accurately described within DFT, including the quantitative features in the reduced density gradient. We elucidate how the enhancement of the exchange energy density at a large reduced density gradient plays a critical role in obtaining accurate DFT description of weakly-interacting systems.