Band gap corrections for molecules and solids using Koopmans theorem and Wannier functions

TL;DR

This paper introduces a parameter-free method based on Koopmans theorem and Wannier functions to correct Kohn-Sham eigen energies in DFT, improving accuracy for molecules and solids with minimal additional computational cost.

Contribution

It presents a general, parameter-free correction method for Kohn-Sham eigen energies applicable to both molecules and solids, enhancing the accuracy of electronic structure calculations.

Findings

Eigen energies for solids match experimental band gaps and band energies.

Molecular eigen energies align well with ionization potentials and electron affinities.

Method outperforms traditional ?SCF in trend accuracy.

Abstract

We have proposed a method for correcting the Kohn-Sham eigen energies in the density functional theory (DFT) based on the Koopmans theorem using Wannier functions. The method provides a general approach applicable for molecules and solids for electronic structure calculations. It does not have any adjustable parameters and the computational cost is at the DFT level. For solids, the calculated eigen energies agree well with the experiments for not only the band gaps, but also the energies of other valence and conduction bands. For molecules, the calculated eigen energies agree well with the experimental ionization potentials and electron affinities, and show better trends than the traditional Delta-self-consistent-field (?SCF) results.