Pressure-induced metallization in solid boron

Different phases of solid boron under high pressure are studied by first principles calculations. The α-B12 structure is found to be stable up to 270 GPa. Its semiconductor band gap (1.72 eV) decreases continuously to zero around 160 GPa, where the material transforms to a weak metal. The metallicity, as measured by the density of states at the Fermi level, enhances as the pressure is further increased. The pressure-induced metallization can be attributed to the enhanced boron-boron interactions that cause bands overlap. These results are consist with the recently observed metallization and the associated superconductivity of bulk boron under high pressure (M.I.Eremets et al, Science293, 272(2001)). 71.20.Nr, 61.50.Ah, 62.50.+p Typeset using REVTEX