Superconductivity of metallic boron in MgB2

Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space fi ller. Band structure calculations indicate that Mg is substantially ionized , and the bands at the Fermi level derive mainly from B orbitals. Strong bo nding with an ionic component and considerable metallic density of states y ield a sizable electron-phonon coupling. Together with high phonon frequenc ies, which we estimate via zone-center frozen phonon calculations to be bet ween 300 and 700 cm(-1), this produces a high critical temperature, consist ent with recent experiments. Thus MgB2 can be viewed as an analog of the lo ng sought, but still hypothetical, superconducting metallic hydrogen.