Localization of Wannier functions for entangled energy bands

TL;DR

This paper introduces a novel method for localizing Wannier functions in entangled energy bands, extending existing algorithms to include additional bands and extract chemical character, demonstrated on semiconductors.

Contribution

It presents a new projective Wannier-Boys localization method that handles entangled bands and incorporates additional bands during optimization.

Findings

Effective localization of unoccupied bands in semiconductors

Successful extraction of chemical character from Bloch waves

Improved localization performance demonstrated on trans-polyacetylene, diamond, and silicon

Abstract

A new method for the localization of crystalline orbitals for entangled energy bands is proposed. It is an extension of the Wannier-Boys algorithm [C. M. Zicovich-Wilson, R. Dovesi, and V. R. Saunders, J. Chem. Phys. 115, 9708 (2001)] which is particularly well-suited for linear combination of atomic orbital representations of the Bloch waves. It allows the inclusion of additional bands during the optimization of the unitary hybridization matrix used in the multi-band Wannier transformation. By a projection technique, the proper chemical character is extracted from the Bloch waves and compact localized orbitals are obtained even for entangled bands. The performance of the new projective Wannier-Boys localization is demonstrated on the low-lying unoccupied bands of trans-polyacetylene, diamond and silicon.