Borophene layers on an Al(111) surface – the finding of a borophene layer with hexagonal double chains and B₉ nonagons using ab initio calculations

Abstract

We studied the stability of several borophene layers on an Al(111) surface and found a structure called 9R using ab initio calculations. This layer competes with χ3 and β12 borophene layers and is made up of boron nonagons that form a network of hexagonal boron double chains. Remarkably, it has no B6 hexagon unlike other borophene layers. All three layers lie significantly lower in energy than the honeycomb layer recently reported on the Al(111) surface [W. Li, et al., Sci. Bull., 2018, 63, 282]. We discuss the structural stability and electronic structures of different borophene layers in light of the role of the filling factor f of boron atoms in boron hexagons in a honeycomb layer as well as charge transfer from the Al substrate to the borophene layer as obtained from the Bader charge analysis. The electron localization function shows that the 9R layer has two-center bonding within the nonagon rings and three-center bonding between the rings. Calculations of the phonon spectra show that a free 9R layer is dynamically stable raising the hope of its isolation. The electronic structure shows that in all cases the borophene layer is metallic.

Defects and Strain Engineering of Structural, Elastic, and Electronic Properties of Boron-Phosphide Monolayer: A Hybrid Density Functional Theory Study

“…Viewed from the difference of charge density, these new formed P-P and B-B bonds around the B_v and P_v defects are relatively weak. Only small amounts of electrons are gathered at these chemical bonds, displaying much larger P-P and B-B bond lengths than those in phosphorene (l P-P = 2.22~2.26 Å) [33,34] and borophene (l B-B = 1.61~1.87 Å) [35,36]. Bader charge analysis reveals that the average amounts of electrons gaining/losing for the P/B atom around the defects are obviously smaller than 0.77e in the pure monolayer, indicating weak ion bond interactions between the B and P atoms.…”

Borophene with Large Holes

“…It is interesting to note that, although there has been no systematic study of the formation mechanism of borophene with LHs before, some explored borophene isomers do have LHs. − Liu and co-workers have noticed the possible existence of large holes at high vacancy concentrations but thought that these structures should be amorphous . Karthikeyan and co-authors have proposed an R9 borophene isomer with LHs .…”

“…It is interesting to note that, although there has been no systematic study of the formation mechanism of borophene with LHs before, some explored borophene isomers do have LHs. − Liu and co-workers have noticed the possible existence of large holes at high vacancy concentrations but thought that these structures should be amorphous . Karthikeyan and co-authors have proposed an R9 borophene isomer with LHs . Yi and co-authors have presented a few borophene structures with large honeycomb-shaped large holes, and their calculations showed that the cohesive energies of the borophene isomers with LHs are very similar to that of the α-sheet.…”

“…41 Karthikeyan and co-authors have proposed an R9 borophene isomer with LHs. 42 Yi and co-authors have presented a few borophene structures with large honeycomb-shaped large holes, 43 and their calculations showed that the cohesive energies of the borophene isomers with LHs are very similar to that of the α-sheet. In a review article written by E. Penve and coworkers, 44 a borophene isomer which is similar to the L4 isomer has been shown.…”

2D Elemental Nanomaterials Beyond Graphene

“…Larger clusters such as B 56 , B 70 , B 84 , B 98 , B 112, and B 120 have been predicted as planar or quasi‐planar structures . The predicted structures of borophenes mainly consist of triangular lattice with hexagonal holes . Mannix et al .…”