DFT study of geometries and stability of Bn clusters (n=2-8)

With density functional theory (DFT), the structures and stability of Bn clusters with n=2-8 have been studied. By using the all electron basis, all the geometries have been globally optimized without any symmetry constraint. It is found that all the small Bn (n=2-8) clusters prefer to form planar structures with sp2 bonds, which are in good agreement with others' related studies. Bn and Bn- are also compared. In contrast with the neutral Bn clusters, although B-B distances in Bn - have slight differences, but addition of one electron does not change their structures significantly. As for energies, all the anions are lying lower than their corresponding neutral clusters. In addition, calculations of energetic and electronic properties for all the neutral clusters have been presented. Both of these two properties show that in Bn (n=2-8), B3 and B5 are more stable than others. Vibrational spectra of Bn (n=3-8) clusters have also been discussed. In each spectrum, intensity peaks which are associated with the vibration of boron clusters related to B-B bond stretching can be observed and they are highest. However, among all the Bn clusters, such peaks of B3 and B5 show lower intensity than others. This results suggest that B3 and B5 are relatively more stable, which further demonstrates the conclusion above.