Decisive Role of Interlayer Ionic Couplings for the Electronic Properties of Two-Dimensional Layered Electrides

Two-dimensional (2D) layered electrides have attracted significant attention as a new class of 2D materials owing to the presence of unusual anionic electrons (AEs). The electride layers are more strongly bound by ionic interactions involving AEs compared with van der Waals layers, which is also critical to the physical and chemical properties of the materials. However, to date, the role of interlayer ionic coupling in determining the properties of 2D electrides has been mostly unexplored. Here we use density functional theory calculations to systematically investigate the effect of interlayer ionic couplings associated with AEs on the electronic properties of various existing and proposed layered electrides. A higher density of AEs in the 2D layered spacing leads to stronger localization and interlayer coupling strength, which induces a Stoner-type magnetic instability. In-plane strain can dramatically modify the configuration of AEs, thereby enabling strain engineering of 2D materials. Strikingly, the work function and interlayer binding energy of the layered electrides are distinctly related, which is in stark contrast to those of van der Waals materials. Besides, we suggest Ba2N and Sr2N as promising candidates for new 2D materials owing to their low interlayer binding energies and stable monolayer forms.