An explanation for similarities in properties of α-phase Pu and TiNi alloys

Abstract

References are reviewed which indicate that there are electronic changes in α-phase Pu at several temperatures below ambient. A published theory suggests that periodic lattice distortions (PLDs) can serve the purpose of promoting electrons into holes in the Fermi surface. Therefore PLDs may be responsible for low-temperature Pu metal behavior. Prior publications have shown that there are two modes of electrical conductivity in α-phase Pu. One mode gives a temperature-independent electrical resistivity along the b axis above 125 K. The other mode results in a maximum in electrical resistivity at ~ 100 K, which is seen in measurements parallel to the a- c plane. A positron annihilation experiment has suggested that conduction electron populations may remain nearly the same in all Pu metal phases. The latter experiment may explain why electrical resistivity is almost temperature independent in every Pu metal phase above 125 K. Attention is called to similarities in electrical resistivity and magnetic susceptibility behavior of alpha (α)-phase Pu and TiNi(X) alloys. Theories are examined which can explain why these materials should have the same low-temperature space group (monoclinic, P2 1/m), and why they should have PLDs and charge-density-wave (CDW) states. The similarity in the physical properties of α-Pu and TiNi alloys may be due to the electronic state of a partially filled or a half-filled band. Both materials may be showing states with characteristics between those of localized core states and weakly correlated valence states.