Are light alkali metals still metals under high pressure

@article{Siringo1995AreLA,
  title={Are light alkali metals still metals under high pressure},
  author={Fabio Siringo and Renato Pucci and Giuseppe G. N. Angilella},
  journal={High Pressure Research},
  year={1995},
  volume={15},
  pages={257-265}
}
The extended Hubbard Hamiltonian on a bcc lattice is studied at half-filling and for a finite hopping between next-nearest neighbours, in mean-field approximation . An ionic insulating broken-symmetry phase is predicted for any hydrogenoid bcc solid in the density range \(1.0<r_s <2.6\). The occurrence of an ionic phase would explain the failure to achieve hydrogen metallization at high pressures . Moreover, a metal–insulator transition is expected for sodium in the 100 GPa region. 
SYMMETRY BREAKING AND RESTORING UNDER HIGH PRESSURE: THE “SIMPLE” ALKALI METALS
Light alkali metals such as lithium have been predicted to undergo a metal-insulator transition at high pressure, the insulating phase being characterized by a considerable reduction of lattice
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