Full Coupled-Cluster Reduction for Accurate Description of Strong Electron Correlation

TL;DR

This paper introduces a full coupled-cluster reduction method that employs sparse algebraic operations and iterative screenings to accurately solve the many-body Schrödinger equation, especially for systems with strong electron correlation.

Contribution

It develops a novel full coupled-cluster approach with explicit commutator expansions and screenings, enabling highly accurate solutions for strongly correlated electrons.

Findings

Achieves fast and near-variational convergence.

Provides highly accurate solutions for strong electron correlation.

Utilizes sparse algebraic operations for efficiency.

Abstract

A full coupled-cluster expansion suitable for sparse algebraic operations is developed by expanding the commutators of the Baker-Campbell-Hausdorff series explicitly for cluster operators in binary representations. A full coupled-cluster reduction that is capable of providing very accurate solutions of the many-body Schr\"odinger equation is then initiated employing screenings to the projection manifold and commutator operations. The projection manifold is iteratively updated through the single commutators $\left\langle \kappa \right| [\hat H,\hat T]\left| 0 \right\rangle$ comprised of the primary clusters $\hat T_{\lambda}$ with substantial contribution to the connectivity. The operation of the commutators is further reduced by introducing a correction, taking into account the so-called exclusion principle violating terms, that provides fast and near-variational convergence in many cases.