Magnetic and metal-insulator transitions in metallic hydrogen

Total-energy band calculations using a local-spin-density approximation and the fixed-spin-moment procedure are used to investigate the volume dependence of the magnetic and electronic properties of hydrogen constrained to an fcc unit cell over a range from below the equilibrium volume to the free-atom limit. With increasing volume, the system first undergoes a transition from nonmagnetic to ferromagnetic behavior and then undergoes a second transition from a ferromagnetic metal to a ferromagnetic insulator. The magnetic transition is shown to be second order, but the metal-insulator transition is shown to be higher than second order, in contradiction to previous work. The volume dependence of the zero-field total energy, magnetic moment, electron occupancy, magnetic modulus, band edges, and bandwidths are presented. The s- and p-electron occupancy is shown to vary linearly over the range of volumes considered. © 1991 The American Physical Society.