Accuracy of Electronic Wave Functions in Quantum Monte Carlo: the Effect of High-Order Correlations

TL;DR

This paper investigates the impact of including high-order nucleus-three-electron correlations in quantum Monte Carlo wave functions, showing significant energy improvements in variational calculations but limited effects on fixed-node diffusion results.

Contribution

It introduces an efficient invariant-based algorithm to incorporate high-order correlations into wave functions, enhancing variational Monte Carlo accuracy.

Findings

Significant energy improvements in variational Monte Carlo

Limited impact on fixed-node diffusion Monte Carlo energies

Greater improvements for bosonic than fermionic atoms

Abstract

Compact and accurate wave functions can be constructed by quantum Monte Carlo methods. Typically, these wave functions consist of a sum of a small number of Slater determinants multiplied by a Jastrow factor. In this paper we study the importance of including high-order, nucleus-three-electron correlations in the Jastrow factor. An efficient algorithm based on the theory of invariants is used to compute the high-body correlations. We observe significant improvements in the variational Monte Carlo energy and in the fluctuations of the local energies but not in the fixed-node diffusion Monte Carlo energies. Improvements for the ground states of physical, fermionic atoms are found to be smaller than those for the ground states of fictitious, bosonic atoms, indicating that errors in the nodal surfaces of the fermionic wave functions are a limiting factor.