A DFT study on the geometrical structures, electronic, and spectroscopic properties of inverse sandwich monocyclic boron nanoclusters ConBm (n=1.2; m=6-8)

Recent photoelectron spectroscopy and computational studies have shown that boron ring-centered transition metal-doped inverse sandwich complexes prefer planar or quasi-planar structures which could be a potential building blocks for designing better nanosystems with tailored properties. Due to promising technological applications of different boron nanoclusters, we present a study on the structural, electronic, magnetic, and spectroscopic properties of Co-centered inverted sandwich monocyclic boron nanoclusters with pyramidal, CoBn, and bi-pyramidal, Co2Bn (n = 6-8) shapes. The investigations have been carried out on previously reported stable hexa-, hepta-, and octagonal hole containing pyramidal and bi-pyramidal boron clusters by employing density functional theory calculations with B3LYP hybrid exchange-correlation functional. Our calculation suggests that all the global minima structures have stable planar or quasiplanar symmetrical cyclic motif. The structural stability of clusters has been investigated by analyzing binding energy, thermodynamical parameters, vibrational spectra etc. All parameters indicate that the bi-pyramidal structures (Co2B6, Co2B7, and Co2B8) are more stable than both pristine and singly doped boron nanoclusters. On the contrary, the bi-pyramidal cluster is chemically less stable than the pyramidal clusters (except CoB7) which is supported by the ionization potential, electron affinity, energy gap, and global indices calculations. Molecular electrostatic potential surface and HOMO-LUMO analysis have been carried out to understand the thermodynamically stable clusters that arises due to specific inter/intra-molecular interactions. The presence of magnetic element (Co) in the clusters induces ferromagnetic properties which have been found by investigating the magnetic moment, spin density, and DOS spectra analysis. Size and geometry-dependent properties of boron nanoclusters have been observed as evident from the energy gap and optical absorptions analysis.