Recently reported structural complexity and enhanced temperature superconducting transitions in lithium under pressure have increased the interest in light alkalies, otherwise considered as simple and well-known systems under normal conditions. Here we present an analysis of the pressure-induced Fermi surface deformation in lithium and its relation to the observed complexity. According to our calculations, the Fermi surface becomes increasingly anisotropic with pressure and at $8\mathrm{GPa}$ contacts the Brillouin zone boundary inducing a Hume-Rothery mechanism explaining the bcc-fcc transition. Around $30\mathrm{GPa}$ increasing cooper-like necks and an extended nesting are observed in the Fermi surface in the fcc phase, enhancing the electronic susceptibility response function and inducing a strong phonon softening. This softening, besides preluding the transition to complex structures and providing a better understanding of the observed superconductivity, is expected to induce other yet unexplored anomalies in compressed lithium.

• Received 29 June 2006

DOI:https://doi.org/10.1103/PhysRevB.74.172104