Band selection and disentanglement using maximally-localized Wannier functions: the cases of Co impurities in bulk copper and the Cu (111) surface

TL;DR

This paper adapts maximally-localized Wannier functions within density functional theory to analyze Co impurities in copper and the Cu (111) surface, enabling detailed electronic structure modeling and surface state description.

Contribution

It introduces a Wannier function approach integrated with the Siesta method for studying impurities and surface states in metallic systems, providing a new tool for surface and impurity analysis.

Findings

Successful reduction of Co impurity problem to key electronic bands

Accurate modeling of the Cu (111) surface Shockley state

Validation of Wannier approach for surface state analysis

Abstract

We have adapted the maximally-localized Wannier function approach of [I. Souza, N. Marzari and D. Vanderbilt, Phys. Rev. B 65, 035109 (2002)] to the density functional theory based Siesta method [J. M. Soler et al., J. Phys.: Cond. Mat. 14, 2745 (2002)] and applied it to the study of Co substitutional impurities in bulk copper as well as to the Cu (111) surface. In the Co impurity case, we have reduced the problem to the Co d-electrons and the Cu sp-band, permitting us to obtain an Anderson-like Hamiltonian from well defined density functional parameters in a fully orthonormal basis set. In order to test the quality of the Wannier approach to surfaces, we have studied the electronic structure of the Cu (111) surface by again transforming the density functional problem into the Wannier representation. An excellent description of the Shockley surface state is attained, permitting us to be confident in the application of this method to future studies of magnetic adsorbates in the presence of an extended surface state.