A self-consistent first-principles calculation scheme for correlated electron systems

TL;DR

This paper introduces a self-consistent first-principles calculation scheme based on density-functional theory for correlated electron systems, incorporating a Hubbard interaction term to improve material simulations.

Contribution

It develops a multi-reference DFT approach with a rigorous Hubbard term determination, extending the Kohn-Sham scheme for better correlated electron system modeling.

Findings

Successful application to hydrogen molecules and chains

Demonstrates U as a continuous function of local fluctuations

Provides a practical framework for materials design

Abstract

A self-consistent calculation scheme for correlated electron systems is created based on the density-functional theory (DFT). Our scheme is a multi-reference DFT (MR-DFT) calculation in which the electron charge density is reproduced by an auxiliary interacting Fermion system. A short-range Hubbard-type interaction is introduced by a rigorous manner with a residual term for the exchange-correlation energy. The Hubbard term is determined uniquely by referencing the density fluctuation at a selected localized orbital. This strategy to obtain an extension of the Kohn-Sham scheme provides a self-consistent electronic structure calculation for the materials design. Introducing an approximation for the residual exchange-correlation energy functional, we have the LDA+U energy functional. Practical self-consistent calculations are exemplified by simulations of Hydrogen systems, i.e. a molecule and a periodic one-dimensional array, which is a proof of existence of the interaction strength U as a continuous function of the local fluctuation and structural parameters of the system.