title: Crystal structures of dense lithium: a metal-semiconductor-metal transition.
abstract: Ab initio random structure searching and single-crystal x-ray diffraction have been used to determine the full structures of three phases of lithium, recently discovered at low temperature above 60 GPa. A structure with C2mb symmetry, calculated to be a poor metal, is proposed for the oC88 phase (60-65 GPa). The oC40 phase (65-95 GPa) is found to have a lowest-enthalpy structure with C2cb symmetry, in excellent agreement with the x-ray data. It is calculated to be a semiconductor with a band gap of ∼1  eV at 90 GPa. oC24, stable above 95 GPa, has the space group Cmca, and refined atomic coordinates are in excellent agreement with previous calculations.
authors.affiliation: SUPA, School of Physics and Astronomy, Centre for Science at Extreme Conditions, The University of Edinburgh, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Marqués
authors.forename: M I
authors.initials: MI
authors.lastname: McMahon
authors.forename: E
authors.initials: E
authors.lastname: Gregoryanz
authors.forename: M
authors.initials: M
authors.lastname: Hanfland
authors.forename: C L
authors.initials: CL
authors.lastname: Guillaume
authors.forename: C J
authors.initials: CJ
authors.lastname: Pickard
authors.forename: G J
authors.initials: GJ
authors.lastname: Ackland
authors.forename: R J
authors.initials: RJ
authors.lastname: Nelmes