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

Highlights: • All the PuO_2-xH_x (0 ≤ x ≤ 2) structures have deformation from cubic lattice. • PuOH compounds have the largest cell volumes. • PuO_1.75H_0.25, PuO_0.25H_1.75, and most PuO_1.5H_0.5 structures are antiferromagnetic as PuO₂ while PuOH and most PuO_0.5H_1.5 structures are ferromagnetic as PuH₂. • Formation energies decrease with the increase of H content. • PuO_2-xH_x (0 ≤ x ≤ 1) are insulators, and PuO_2-xH_x (1.5 ≤ x ≤ 1) are metallic. -- 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 PuO_2-xH_x 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 PuO_1.75H_0.25, PuO_0.25H_1.75, and most of PuO_1.5H_0.5 configurations are antiferromagnetic as PuO₂, while PuOH and most of PuO_0.5H_1.5 configurations have the ferromagnetic ground state as PuH₂. The magnetic moment per Pu rises with the increase of x and reaches the maximum at PuO_0.25H_1.75. Densities of states are computed with HSE functional, demonstrating that PuO₂, PuO_1.75H_0.25, PuO_1.5H_0.5, and PuOH are all insulators and PuO_0.5H_1.5, PuO_0.25H_1.75, and PuH₂ are metals. Therefore, the insulator-metal transition for PuO_2-xH_x occurs at 1 < x < 1.5. Moreover, the formation energies for PuO_2-xH_x are calculated, showing that the reactions become more and more exothermic with the decrease of x.