Anionic character of the conduction band of sodium chloride

Christopher C Leon; Abhishek Grewal; Klaus Kuhnke; Klaus Kern; Olle Gunnarsson

doi:10.1038/s41467-022-28392-8

Anionic character of the conduction band of sodium chloride

Nat Commun. 2022 Feb 21;13(1):981. doi: 10.1038/s41467-022-28392-8.

Authors

Christopher C Leon^#¹, Abhishek Grewal^#¹, Klaus Kuhnke², Klaus Kern^{1

3}, Olle Gunnarsson⁴

Affiliations

¹ Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569, Stuttgart, Germany.
² Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569, Stuttgart, Germany. [email protected].
³ Institut de Physique, École Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.
⁴ Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569, Stuttgart, Germany. [email protected].

^# Contributed equally.

Abstract

The alkali halides are ionic compounds. Each alkali atom donates an electron to a halogen atom, leading to ions with full shells. The valence band is mainly located on halogen atoms, while, in a traditional picture, the conduction band is mainly located on alkali atoms. Scanning tunnelling microscopy of NaCl at 4 K actually shows that the conduction band is located on Cl^- because the strong Madelung potential reverses the order of the Na⁺ 3s and Cl^- 4s levels. We verify this reversal is true for both atomically thin and bulk NaCl, and discuss implications for II-VI and I-VII compounds.