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

Abstract

A self-consistent calculation scheme for correlated electron systems is created based on thedensity-functional theory (DFT). Our scheme is a multi-reference DFT (MR-DFT)calculation in which the electron charge density is reproduced by an auxiliary interactingfermion system. A short-range Hubbard-type interaction is introduced in a rigorous mannerwith a residual term for the exchange–correlation energy. The Hubbard term isdetermined uniquely by referencing the density fluctuation at a selected localizedorbital. This strategy to obtain an extension of the Kohn–Sham scheme provides aself-consistent electronic structure calculation for the materials design. Introducing twoapproximations for the residual exchange–correlation energy functional, we have theLDA + U energy functional. Practical self-consistent calculations are exemplifiedby simulations of hydrogen systems, i.e. a molecule and a periodicone-dimensional array, which is a proof of existence of the interaction strengthU as a continuous function of the local fluctuation and structural parameters of the system.