Chemical accuracy from quantum Monte Carlo for the Benzene Dimer

TL;DR

This study demonstrates that quantum Monte Carlo methods can achieve chemical accuracy in calculating weak van der Waals interactions, specifically for the Benzene dimer, outperforming many density functional theory approaches.

Contribution

The paper introduces highly optimized trial wave functions in QMC to accurately compute the Benzene dimer's binding energy, achieving results comparable to high-level quantum chemistry methods.

Findings

QMC yields binding energies of -2.3 and -2.7 kcal/mol for Benzene dimer.

Optimized wave functions improve the accuracy of weak interaction calculations.

QMC methods reach chemical accuracy for van der Waals interactions.

Abstract

We report an accurate study of interactions between Benzene molecules using variational quantum Monte Carlo (VMC) and diffusion quantum Monte Carlo (DMC) methods. We compare these results with density functional theory (DFT) using different van der Waals (vdW) functionals. In our QMC calculations, we use accurate correlated trial wave functions including three-body Jastrow factors, and backflow transformations. We consider two benzene molecules in the parallel displaced (PD) geometry, and find that by highly optimizing the wave function and introducing more dynamical correlation into the wave function, we compute the weak chemical binding energy between aromatic rings accurately. We find optimal VMC and DMC binding energies of -2.3(4) and -2.7(3) kcal/mol, respectively. The best estimate of the CCSD(T)/CBS limit is -2.65(2) kcal/mol [E. Miliordos et al, J. Phys. Chem. A 118, 7568 (2014)]. Our results indicate that QMC methods give chemical accuracy for weakly bound van der Waals molecular interactions, comparable to results from the best quantum chemistry methods.