Electronic structure and phase stability of plutonium hydrides: Role of Coulomb repulsion and spin-orbital coupling

摘要

The electronic and magnetic states, chemical bonding and reactions, and phonon spectrum of the plutonium hydrides PuH_x (x = 2, 3) are investigated by employing first-principles calculations by means of the density functional theory (DFT) + U approach. The strong correlation and the spin-orbit coupling (SOC) effects on these 5f electrons systems are systematically studied. Results show that both the strong correlation and the SOC play critical roles in correctly describing their ground-state properties. The antifer-romagnetic configuration of PuH_2 is found energetically most stable while for PuH_3 the ferromagnetic state is the most stable state. Our calculated phonon spectra clearly indicate the dynamical stability of these magnetic configurations. For PuH_3, more electrons from the Pu atoms are released to bond with H than that in PuH_2. As a result, the lattice constant is contracted by increasing the H concentration. Reacting from metal Pu and molecule H_2, more PuH_3 should be produced than PuH_2 in low temperature condition.