Theoretical confirmation of Ga-stabilized anti-ferromagnetism in plutonium metal

Density functional theory (DFT) for plutonium metal is shown to be consistent with recent magnetic measurements that suggest anti-ferromagnetism in Pu-Ga alloys at low temperatures. The theoretical model predicts a stabilization of the face-centered-cubic (fcc, δ) form of plutonium in an anti-ferromagnetic configuration when alloyed with gallium. The ordered magnetic phase occurs because Ga removes the mechanical instability that exists for unalloyed δ-Pu. The cause of the Ga-induced stabilization is a combination of a lowering of the band (kinetic) and electrostatic (Coulomb) energies for the cubic relative to the tetragonal phase. Similarly, gallium plays an important role in stabilizing anti-ferromagnetism in the tetragonal P4/mmm Pu3Ga compound.