Phase stabilization in the light actinides and binary alloys

Abstract

From a phenomenological analysis of phase stabilization in the binary actinide alloy systems, U–Pu, U–Np–Pu and U–transition metals, the existence of a relatively stable electronic complex with the configuration (5f nd)v is deduced. It must be formed by itinerant 5f and nd electron states with n=3, 4, 5, 6 and v should be a fractional number since only band states are involved. The stability of the complexes should depend on temperature. In α-Pa, equal numbers of 5f and 6d states in the valence electron system result: (i) in a (5f6d)* supercomplex which correlates with the unique crystal structure of α-Pa and (ii) with metal properties which rather resemble those of α-Th than that of α-U. The alleged properties of the complex are discussed and compared with the thermal behavior of α-Pa and of the α-U on approaching the α/β transition temperatures and Pa should play a key role for understanding the temperature effects in the light actinide series. In a following paper, the literature on fabrication and properties of Pa metal is critically reviewed for the comparison of relevant properties between α-Th, α-Pa and α-U.