Local density approximation in site-occupation embedding theory

TL;DR

This paper introduces a new local density approximation within site-occupation embedding theory (SOET) for modeling strongly correlated electrons, demonstrating promising results on small Hubbard systems.

Contribution

The paper proposes a simple impurity-occupation functional approximation called 2L-ILDA based on the two-level Hubbard model for SOET.

Findings

Promising results on an 8-site Hubbard ring.

Extension to larger systems is underway.

Abstract

Site-occupation embedding theory (SOET) is a density-functional theory (DFT)-based method which aims at modelling strongly correlated electrons. It is in principle exact and applicable to model and quantum chemical Hamiltonians. The theory is presented here for the Hubbard Hamiltonian. In contrast to conventional DFT approaches, the site (or orbital) occupations are deduced in SOET from a partially-interacting system consisting of one (or more) impurity site(s) and non-interacting bath sites. The correlation energy of the bath is then treated implicitly by means of a site-occupation functional. In this work, we propose a simple impurity-occupation functional approximation based on the two-level (2L) Hubbard model which is referred to as two-level impurity local density approximation (2L-ILDA). Results obtained on a prototypical uniform 8-site Hubbard ring are promising. The extension of the method to larger systems and more sophisticated model Hamiltonians is currently in progress.