Boron could be the next element after carbon capable of forming 2D-materials similar to graphene. Theoretical calculations predict that the most stable planar all-boron structure is the so-called α-sheet. The mysterious structure of the α-sheet with peculiar distribution of filled and empty hexagons is rationalized in terms of chemical bonding. We show that the hexagon holes serve as scavengers of extra electrons from the filled hexagons. This work could advance rational design of all-boron nanomaterials.

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Two low-lying structures are unveiled for the Be B nanocluster system that are virtually isoenergetic. The first, triple-layered cluster has a peripheral B ring as central layer, being sandwiched by two Be rings in a coaxial fashion, albeit with no discernible interlayer Be-Be bonding. The B ring revolves like a flexible chain even at room temperature, gliding freely around the Be prism. At elevated temperatures (1000 K), the Be core itself also rotates; that is, two Be rings undergo relative rotation or twisting with respect to each other. Bonding analyses suggest four-fold (π and σ) aromaticity, offering a dilute and fluxional electron cloud that lubricates the dynamics. The second, helix-type cluster contains a B helical skeleton encompassing a distorted Be prism. It is chiral and is the first nanosystem with a boron helix. Molecular dynamics also shows that at high temperature the helix cluster readily converts into the triple-layered one.