Data-Driven Design of Two-Dimensional Non-van der Waals Materials

Two-dimensional (2D) materials are traditionally associated with the
sheets forming bulk layered compounds bonded by weak van der Waals
(vdW) forces. The weak inter-layer interaction leads to a natural structural
separation of the 2D subunits in the crystals, giving rise to the
possibility of mechanical and liquid-phase exfoliation as well as enabling
the formulation of exfoliability descriptors.
The unexpected experimental realization of non-vdW 2D compounds,
for which the previously formulated descriptors are not
applicable, opened up a new direction in the research on 2D systems
[1]. Here, we present our recent data-driven search for representatives
of this novel materials class [2]. By screening the AFLOW database
according to structural prototypes, 28 potentially synthesizable candidates
are outlined. The oxidation state of the surface cations is
found to regulate the exfoliation energy with low oxidation numbers
giving rise to weak bonding — thus providing an enabling descriptor
to obtain novel 2D materials. The candidates showcase a diverse
spectrum of appealing electronic, optical and magnetic features.
[1] A. Puthirath Balan et al., Nat. Nanotechnol. 13, 602 (2018).
[2] R. Friedrich et al., Nano Lett. 22, 989 (2022).