# Suppressing ionic terms with number counting Jastrow factors in real space

## TL;DR

This paper introduces 4-body real space Jastrow factors that effectively remove ionic terms from wave functions, improving size consistency and compatibility with diffusion Monte Carlo, leading to more accurate strongly correlated trial functions.

## Contribution

It presents a novel use of 4-body Jastrow factors for wave function stenciling to eliminate ionic terms, enhancing size consistency and DMC compatibility in quantum Monte Carlo methods.

## Key findings

- Successfully removes ionic terms from wave functions
- Restores size consistency exactly in geminal power cases
- Produces qualitatively correct nodal surfaces in double bond dissociation

## Abstract

We demonstrate that 4-body real space Jastrow factors are, with the right type of Jastrow basis function, capable of performing successful wave function stenciling to remove unwanted ionic terms from an overabundant fermionic reference without unduly modifying the remaining components. In addition to greatly improving size consistency (restoring it exactly in the case of a geminal power), real-space wave function stenciling is, unlike its Hilbert space predecessors, immediately compatible with diffusion Monte Carlo, allowing it to be used in the pursuit of compact, strongly correlated trial functions with reliable nodal surfaces. We demonstrate the efficacy of this approach in the context of a double bond dissociation by using it to extract a qualitatively correct nodal surface despite being paired with a restricted Slater determinant, that, due to ionic term errors, produces a ground state with a qualitatively incorrect nodal surface when used in the absence of the Jastrow.