Transition state method and Wannier functions

TL;DR

This paper introduces a new computational approach combining transition state approximation and Wannier functions to improve excitation energy predictions in materials where standard LDA fails, showing better agreement with experiments.

Contribution

It develops a correction to the LDA functional that yields excitation energies consistent with transition state calculations using Wannier functions.

Findings

Improved energy gap predictions for MgO, Si, NiO, and BaBiO3.

Better agreement with experimental excitation energies than standard LDA.

Applicable to materials with challenging electronic excitation descriptions.

Abstract

We propose a computational scheme for materials where standard Local Density Approximation (LDA) fails to produce a satisfactory description of excitation energies. The method uses Slater's "transition state" approximation and Wannier functions basis set. We define a correction to LDA functional in such a way that its variation produces one-electron energies for Wannier functions equal to the energies obtained in "transition state" constrained LDA calculations. In the result eigenvalues of the proposed functional could be interpreted as excitation energies of the system under consideration. The method was applied to MgO, Si, NiO and BaBiO$_3$ and gave an improved agreement with experimental data of energy gap values comparing with LDA.