Constrained-Pairing Mean-Field Theory. IV. Inclusion of corresponding pair constraints and connection to unrestricted Hartree-Fock theory

TL;DR

This paper extends Constrained-Pairing Mean-Field Theory by incorporating pair constraints, connecting it to unrestricted Hartree-Fock, and enabling accurate dissociation of polyatomic molecules.

Contribution

It introduces a new version of CPMFT with pair constraints, linking it to UHF and improving molecular dissociation accuracy.

Findings

CPMFT maps onto UHF with pair constraints.

The new CPMFT version correctly dissociates molecules.

Maintains advantages of independent particle models.

Abstract

Our previously developed Constrained-Pairing Mean-Field Theory (CPMFT) is shown to map onto an Unrestricted Hartree-Fock (UHF) type method if one imposes a corresponding pair constraint to the correlation problem that forces occupation numbers to occur in pairs adding to 1. In this new version, CPMFT has all the advantages of standard independent particle models (orbitals and orbital energies, to mention a few), yet unlike UHF, it can dissociate polyatomic molecules to the correct ground-state restricted open-shell Hartree-Fock atoms or fragments.