First-principles study of the electronic structures of α-rhombohedral boron codoped with lithium and oxygen

α-Rhombohedral (α-rh) boron, which is the most stable of boronʹs polymorphs at low temperatures, has p-type semiconductive properties. There have been some attempts to dope the interstitial sites with alkali atoms to create metallic or n-type semiconductive α-rh boron, but this has yet to be achieved. In a previous work, we proposed the codoping of α-rh boron with Li and P or As, and revealed from first principles calculations that B12PLi and B12AsLi could be synthesized and become narrow-gap semiconductors. The band structure suggested that the mobility of electrons might be greater than that of holes. In this paper, based on these prospective results, we selected a new combination of dopants, Li and O, and theoretically studied such compounds as B12OLi and B12O2Li. The results showed that both of these materials are metallic, while the reaction energies of the Li insertion into B12O and B12O2 are lower (more unstable) than with B12PLi and B12AsLi. It was proved that the differences in the electronic structures are caused by the dangling bonds of the dopant atoms, O, P and As.