Many-Body Expanded Full Configuration Interaction. I. Weakly Correlated Regime

TL;DR

This paper demonstrates the effectiveness of the many-body expanded full configuration interaction (MBE-FCI) method in accurately computing ground state energies for weakly correlated molecules across various spin states, advancing FCI-level computational chemistry.

Contribution

It introduces performance enhancements of the MBE-FCI method, showing its capability to produce near-exact energies for weakly correlated molecules of any spin multiplicity.

Findings

MBE-FCI achieves near-exact ground state energies.

The method is versatile across different spin states.

It is effective for medium to large basis sets.

Abstract

Over the course of the past few decades, the field of computational chemistry has managed to manifest itself as a key complement to more traditional lab-oriented chemistry. This is particularly true in the wake of the recent renaissance of full configuration interaction (FCI)-level methodologies, albeit only if these can prove themselves sufficiently robust and versatile to be routinely applied to a variety of chemical problems of interest. In the present series of works, performance and feature enhancements of one such avenue towards FCI-level results for medium to large one-electron basis sets, the recently introduced many-body expanded full configuration interaction (MBE-FCI) formalism [J. Phys. Chem. Lett., 8, 4633 (2017)], will be presented. Specifically, in this opening part of the series, the capabilities of the MBE-FCI method in producing near-exact ground state energies for weakly correlated molecules of any spin multiplicity will be demonstrated.