Molecular hydrogen adsorbed on benzene: insights from a quantum Monte Carlo study

TL;DR

This study uses quantum Monte Carlo methods to accurately analyze the weak binding interaction between hydrogen and benzene, emphasizing the importance of diffuse orbitals and correlation effects.

Contribution

It demonstrates that quantum Monte Carlo can reliably compute weak hydrogen-benzene binding energies, highlighting the role of diffuse basis functions and correlation in the interaction.

Findings

VMC and DMC binding energies agree within 0.18 mHa.

Binding energies are consistent across different trial wave functions.

The study clarifies the physical mechanisms and charge redistribution involved.

Abstract

We present a quantum Monte Carlo study of the hydrogen-benzene system where binding is very weak. We demonstrate that the binding is well described at both variational Monte Carlo (VMC) and diffusion Monte Carlo (DMC) levels by a Jastrow correlated single determinant geminal wave function with an optimized compact basis set that includes diffuse orbitals. Agreement between VMC and fixed-node DMC binding energies is found to be within 0.18 mHa, suggesting the calculations are well-converged with respect to the basis. Essentially the same binding is also found in independent DMC calculations using a different trial wave function of a more conventional Slater-Jastrow form, supporting our conclusion that the binding energy is accurate and includes all effects of correlation. We compare with empirical models and previous calculations, and we discuss the physical mechanisms of the interaction, the role of diffuse basis functions, and the charge redistribution in the bond.