Quantum Monte Carlo calculations of van der Waals interactions between aromatic benzene rings

TL;DR

This paper investigates finite-size effects and Coulomb interactions in quantum Monte Carlo simulations of van der Waals forces between benzene molecules, highlighting the importance of finite-size errors and comparing trial wave functions.

Contribution

It evaluates the impact of finite-size errors and trial wave functions on quantum Monte Carlo calculations of benzene interactions and properties.

Findings

Finite-size errors significantly affect energy difference calculations.

Backflow transformation impacts non-local correlation energy.

Quantum Monte Carlo can compute cohesive and energy gaps in benzene.

Abstract

The magnitude of finite-size effects and Coulomb interactions in quantum Monte Carlo simulations of van der Waals interactions between weakly bonded benzene molecules are investigated. To that extent, two trial wave functions of the Slater-Jastrow and Backflow-Slater-Jastrow types are employed to calculate the energy-volume equation of state. We assess the impact of the backflow coordinate transformation on the non-local correlation energy. We found that the effect of finite-size errors in quantum Monte Carlo calculations on energy differences is particularly large and may even be more important than the employed trial wave function. Beside the cohesive energy, the singlet excitonic energy gap and the energy gap renormalization of crystalline benzene at different densities are computed.