Discovering Two-Dimensional Non-van der Waals Materials by Data-driven Research

While two-dimensional (2D) materials are traditionally associated with bulk layered
compounds bonded by weak van der Waals (vdW) interactions, the recent surprising
experimental realization of non-vdW 2D systems obtained from non-layered crystals [1,2]
opens up a new direction. These materials show several distinct differences to traditional
2D sheets as their surface was revealed to be terminated by cations rather than anions.
Here, we outline several dozens of candidates of this novel materials class derived from
employing data-driven research principles in conjunction with autonomous ab initio
calculations [3,4] (Figure 1). The oxidation state of the surface cations of the 2D sheets
turns out to be an enabling descriptor regarding the manufacturing of these systems as
it determines their exfoliation energy: small oxidation states promote easy peel off [3].
When extending the set from oxides to sulfides and chlorides, the exfoliation energy
becomes ultra low due to strong surface relaxations [4]. The candidates exhibit a wide
range of appealing electronic, optical and in particular magnetic properties making these
systems an attractive platform for fundamental and applied nanoscience.
[1] A. Puthirath Balan et al., Nat. Nanotechnol. 13, 602 (2018).
[2] A. Puthirath Balan et al., Chem. Mater. 30, 5923 (2018).
[3] R. Friedrich et al., Nano Lett. 22, 989 (2022).
[4] T. Barnowsky et al., Adv. Electron. Mater. 9, 2201112 (2023).