Strong correlations via constrained-pairing mean-field theory

TL;DR

This paper introduces a constrained-pairing mean-field theory (CPMFT) that accurately models strong electron correlations by focusing on electron pairings within an active space, preserving key symmetries and improving upon traditional methods.

Contribution

The paper presents a novel mean-field approach, CPMFT, that captures strong correlations through a two-particle density matrix ansatz while maintaining spin and spatial symmetries.

Findings

Accurately describes metal-insulator transition in hydrogen clusters

Effectively models molecular dissociation curves

Preserves symmetries despite electron number fluctuations

Abstract

We present a mean-field approach for accurately describing strong correlations via electron number fluctuations and pairings constrained to an active space. Electron number conservation is broken and correct only on average but both spin and spatial symmetries are preserved. Optimized natural orbitals and occupations are determined by diagonalization of a mean-field Hamiltonian. This constrained-pairing mean-field theory (CPMFT) yields a two-particle density matrix ansatz that exclusively describe strong correlations. We demonstrate CPMFT accuracy with applications to the metal-insulator transition of large hydrogen clusters and molecular dissociation curves.