Population Analysis with Wannier Orbitals

TL;DR

This paper introduces Wannier orbital overlap and Hamilton population methods to analyze electron distribution and bonding in materials, bridging plane-wave DFT calculations with localized orbital insights.

Contribution

It develops a formalism to connect plane-wave DFT with localized Wannier orbitals, enabling detailed bonding analysis with zero spilling factor for insulators.

Findings

Provides a new method for bonding analysis in materials.

Achieves zero spilling factor in insulators.

Demonstrates applicability on five different materials.

Abstract

We formulate Wannier orbital overlap population and Wannier orbital Hamilton population to describe the contribution of different orbitals to electron distribution and their interactions. These methods, which are analogous to the well known crystal orbital overlap population and crystal orbital Hamilton population, provide insight into the distribution of electrons at various atom centres and their bonding nature. We apply this formalism in the context of a plane-wave density functional theory calculation. This method provides a means to connect the non-local plane-wave basis to a localised basis by projecting the wave functions from a plane-wave density functional theory calculation on to localized Wannier orbital basis. The main advantage of this formulation is that the spilling factor is strictly zero for insulators and can systematically be made small for metals. We use our proposed method to study and obtain bonding and electron localization insights in five different materials.