First-principles study on metal-doped icosahedral B-12 solids

Theoretical exploration of a group of ''C-60-like'' B-12-based materials, A(x)B(12). With A=(Li and Ca) and x=1-4, is made by performing local-density approximation Gaussian basis calculations of the total energy, heats of formation, lattice constant, electronic structure, density of states, and bulk modulus of the putative compounds, using ab initio pseudopotentials. Lithium-doped materials are mostly demonstrated to give sufficient heats of formation, whereas it is shown that all Ca-doped materials are unstable, including Li2CaB12. Results are presented only for the stable and metastable LixB12 and compared with other current theoretical calculations on K3C60 The possibility of superconductivity is also discussed. The band-structure calculations reveal essentially metallic behavior of LixB12. Important differences are found in the energy band structures, particularly in bands near the Fermi level, that would be reflected in superconductivity of these systems. Favorable superconducting properties are expected for Li3B12, in the context of sufficiently high N(E(F)) and obtained bulk modulus that is indicative of strong electron-phonon coupling.