Variational calculation of many-body wave functions and energies from density-functional theory

TL;DR

This paper introduces a variational method that constructs many-body wave functions from density-functional theory solutions by superposing Kohn-Sham determinants with a generating coordinate, improving the calculation of energies and states.

Contribution

It presents a novel approach combining DFT with a superposition of Kohn-Sham determinants to accurately compute many-body wave functions and energies.

Findings

Method works for ground and excited states

Does not require identifying KS orbitals with physical orbitals

Numerical tests on Helium series demonstrate viability

Abstract

A generating coordinate is introduced into the exchange-correlation functional of density-functional theory (DFT). The many-body wave function is represented as a superposition of Kohn-Sham (KS) Slater determinants arising from different values of the generating coordinate. This superposition is used to variationally calculate many-body energies and wave functions from solutions of the KS equation of DFT. The method works for ground and excited states, and does not depend on identifying the KS orbitals and energies with physical ones. Numerical application to the Helium isoelectronic series illustrates the method's viability and potential.