Spin-constrained Hartree-Fock and the generator coordinate method for the 2-site Hubbard model

TL;DR

This paper analyzes spin-constrained Hartree-Fock solutions of the 2-site Hubbard model, highlighting symmetry breaking and their use as basis states in the Generator Coordinate Method for electron correlation.

Contribution

It provides a mathematical analysis of CHF solutions and demonstrates their application as basis states in GCM for multiconfigurational calculations.

Findings

Insights into spin symmetry breaking around the Coulson-Fischer point

CHF states serve as effective basis states in GCM

Enhanced understanding of static electron correlation

Abstract

We present a mathematical analysis of the spin-constrained Hartree-Fock solutions (CHF) of the 2-site Hubbard model. The analysis sheds light on the spin symmetry breaking process around the Coulson-Fischer point. CHF states are useful as input states for the Generator Coordinate Method (GCM) in which CHF states can be used as a basis for multiconfigurational calculations in the Hill-Wheeler equations. The spin degree of freedom provides the generator coordinate in the GCM related to static electron correlation.