It was noted that the B in MgB2 formed stacks of honeycomb layers with Mg as a space-filler. Band-structure calculations indicated that Mg was substantially ionized, and that the bands at the Fermi level arose mainly from B orbitals. Strong bonding with an ionic component and considerable metallic density of states yielded sizable electron-phonon coupling. High phonon frequencies were estimated, via zone-center frozen phonon calculations, to be between 300 and 700/cm. This produced a high critical temperature, consistent with experiment. Thus MgB2 could be viewed as being an analogue of the hypothetical superconductor, metallic H.

Superconductivity of Metallic Boron in MgB2. J.Kortus, I.I.Mazin, K.D.Belashchenko, V.P.Antropov, L.L.Boyer: Physical Review Letters, 2001, 86[20], 4656-9