Superconductivity in lithium under pressure

We use an ab initio calculation, within the framework of the density functional theory, to calculate total energy, electronic energy bands, and the phonon dispersion curves of an fcc structure of lithium as a function of the unit cell volume. We find that the fcc structure is stable starting from a reduced volume of 0.88 V ₀, where V ₀ is the known unit cell volume at ambient pressure and it remains so until a volume of 0.40 V ₀. The electronic structure and the vibrational modes are calculated, as well as the variation of T _c with the volume. At a reduced volume of 0.40 V ₀, T _c is calculated to be 20 K, which is in agreement with the experimental value. Our calculations indicate that superconductivity in Li under high-pressure occurs through intervalley scattering of electrons, between pockets centered at the L-points of the Brillouin zone (BZ), mediated by phonons in the vicinity of the X-points.