First-principles calculation of structural, magnetic and electronic properties of PuO2-xHx, 0≤x≤2

Abstract

First-principles calculations with generalized gradient approximation (GGA) plus U method as well as Heyd-Scuseria-Ernzerhof (HSE) screened Coulomb hybrid density functional including spin-orbit coupling effect are performed to investigate the structural, magnetic, electronic properties and formation energies for the PuO2-xHx compounds in fluorite structure, where 0 ≤ x ≤ 2. It is found that the cubic lattice tends to have a tetragonal deformation due to the magnetic ordering. PuOH has the largest lattice among the concerned structures. HSE calculations show that PuO1.75H0.25, PuO0.25H1.75, and most of PuO1.5H0.5 configurations are antiferromagnetic as PuO2, while PuOH and most of PuO0.5H1.5 configurations have the ferromagnetic ground state as PuH2. The magnetic moment per Pu rises with the increase of x and reaches the maximum at PuO0.25H1.75. Densities of states are computed with HSE functional, demonstrating that PuO2, PuO1.75H0.25, PuO1.5H0.5, and PuOH are all insulators and PuO0.5H1.5, PuO0.25H1.75, and PuH2 are metals. Therefore, the insulator-metal transition for PuO2-xHx occurs at 1 < x < 1.5. Moreover, the formation energies for PuO2-xHx are calculated, showing that the reactions become more and more exothermic with the decrease of x.