Search for the largest two-dimensional aggregates of boron: An ab initio study

We use ab initio density functional calculations to investigate the structural stability and vibrational spectra of small boron aggregates in different charge states. In search of candidates for the largest stable 2D boron aggregates, we focus on systems with one atom less than ${\mathrm{B}}_{20}$ clusters with confirmed 3D geometry. Whereas the most stable structural isomer of ${\mathrm{B}}_{19}^{-}$ is two-dimensional, in agreement with experimental results of Huang et al. [Nat. Chem. 2, 202 (2010)], the second most stable anionic and the most stable neutral and cationic species form a 3D pyramidal structure that had been missed previously.

Figure 1

Equilibrium geometry and total energy differences, corrected for zero-point energies, between different structural isomers of ${\mathrm{B}}_{19}^{-}$ anion clusters. For selected structures, the varying degree of planarity is depicted in top and side view.

Figure 2

Vibrational spectra of stable ${\mathrm{B}}_{19}^{-}$ isomers, convoluted with a 50-cm${}^{-1}$ full width at half maximum Gaussian function. The labeling of the structural isomers follows Fig. 1.