A bottom-up approach from medium-sized bilayer boron nanoclusters to bilayer borophene nanomaterials

Inspired by the experimentally observed bilayer B-48(-/0) and theoretically predicted bilayer B-50-B-72 and based on extensive density functional theory calculations, we report herein a series of novel medium-sized bilayer boron nanoclusters C-1 B-84 (I), C-2v B-86 (II), C-1 B-88 (III), C-1 B-90 (IV), C-1 B-92 (V), C-1 B-94 (VI), C-2v B-96 (VII), and C-1 B-98 (VIII) which are the most stable isomers of the systems reported to date effectively stabilized by optimum numbers of interlayer B-B sigma bonds between the inward-buckled atoms on top and bottom layers. Detailed bonding analyses indicate that these bilayer species follow the universal bonding pattern of sigma + pi double delocalization, rendering three-dimensional aromaticity in the systems. More interestingly, the AA-stacked bilayer structural motif in B-96 (VII) with a B-72 bilayer hexagonal prism at the center can be extended to form bilayer C-2 B-128 (IX), D-2h B-214 (X), C-2v B-260 (XI), D-2h B-372 (XII), and D-2 B-828 (XIII) which contain one or multiple conjoined B-72 bilayer hexagonal prisms sharing interwoven zig-zag boron triple chains between them. Such bilayer species or their close-lying AB isomers can be viewed as embryos of the newly reported most stable freestanding BL-alpha(+) bilayer borophenes and quasi-freestanding bilayer borophenes on Ag(111) which are composed of interwoven zig-zag boron triple chains shared by conjoined BL B-72 hexagonal prisms, presenting a bottom-up approach from medium-sized bilayer boron nanoclusters to two-dimensional bilayer borophene nanomaterials.

Automated summary

Inspired by experimental observations and theoretical predictions, this study reports a series of novel medium-sized bilayer boron nanoclusters. Through extensive calculations, these clusters are shown to be stabilized by interlayer B-B sigma bonds. The bonding analysis reveals the presence of three-dimensional aromaticity in these bilayer species. Additionally, the bilayer structures can further develop into newly reported bilayer borophenes, demonstrating a bottom-up approach towards two-dimensional nanomaterials.