A computational study on the endohedral alkali metal and ion B40 nanocluster.

Recent exploration of the boron fullerenes has raised exciting new prospects for boron applications. Here, the endohedral X/X+@B40 complexes (X = Li, Na, and K) were explored by means of density functional theory calculations. By increasing the atomic number, the interaction of alkali metals with the B40 nanocage is unusually weakened. It was concluded that by increasing the alkali metals' size, their electrons repel those of the cage, and the interaction weakens. The interaction of X with B40 is more favorable than that of X+. For example, the calculated ΔG of interaction at 298 K and 1 atm is about -108.3 and + 18.4 kJ mol-1 for X and X+, respectively. Compared to the X+ cations, the X atoms considerably enhance the boron cluster electrical conductivity, by reducing the gap. We found that the B40 nanocluster is not large enough to freely embed large atoms, such as Na and K. Also, the electron emission from the surface of B40 cluster is increased and reduced by X and X+ encapsulations, respectively.