The electronic ground states of UAl/sub 2/, NpAl/sub 2/ and PuAl/sub 2/ have been determined by band theory techniques. These calculations indicate that both actinide d-f hybridization and spin-orbit coupling are important in these systems. Using a new scheme for obtaining the paramagnon parameters for UAl/sub 2/ it is shown that calculated and experimentally derived 5f band width are consistent. The fact that orbital angular momentum may not be quenched in these systems is suggested as a possible mechanism for damping spin-fluctuations in NpAl/sub 2/ and PuAl/sub 2/.
Argonne National Laboratory is currently developing an electro-metallurgical process for treating a wide array of spent nuclear fuels. As part of this process, two waste streams will be consolidated into waste forms; one will be a mineral and the other a metal alloy. The metal waste form is an alloy that contains cladding hulls, ``noble`` metal fission products, and Zr from alloy fuels. The nominal composition of the metal waste form alloys are stainless steel-15 wt.% Zr (SS-15Zr) for stainless steel clad fuel and Zircaloy-8 wt.% stainless steel (Zr-8SS) for Zircaloy clad fuel, with both alloys also containing up to 4 wt.% noble metal fission products. This paper investigates using the two nominal metal alloy compositions described above as a possible Pu and TRU disposition form.
The first US magnetism conference occurred in 1952 and featured an invited session on exchange coupling in metals with Zener, Slater, Wohlfarth and Van Vleck speaking. All were concerned with intra- and interatomic exchange with Zener discussing coupling via conduction electron polarization while Wohlfarth and Slater were preoccupied with itinerant ferromagnetism. Van Vleck verbalized the Hubbard Hamiltonian (prior to its derivation). That meeting may be viewed as the ultimate discussion of magnetism prior to modern day computation and many of the ideas expressed there underlie our computational activities today. Solutions of the Hubbard Hamiltonian and electronic structure calculations, as applied to magnetism, come to mind. We will concentrate on the latter here, since solving the Hubbard Hamiltonian will be of great concern elsewhere in this meeting, and we will attempt to juxtapose current findings with some of the thoughts of that pioneering meeting. 30 refs., 5 figs.
Date: January 1, 1989
Creator: Watson, R.E. (Brookhaven National Lab., Upton, NY (USA))
The materials CeSn/sub 3/, USn/sub 3/, and NpSn/sub 3/ are all moderately heavy Fermion compounds with electronic specific heat coefficients of 73, 169, and 242 mJ/mole K/sup 2/. CeSn/sub 3/ is known as a mixed valent system and NpSn/sub 3/ is a weak itinerant antiferromagnet. All three are strongly enhanced. Being in the relatively simple Au/sub 3/Cu structure, they form an excellent set of materials to study as representatives of strongly enhanced systems. One would like to ascertain what properties can be determined from band calculations based on density functional theory in the local density approximation. It has already been shown that the Fermi surface topology of CeSn/sub 3/ can be well described in this way even though the experimental masses are much larger than the band results. The enhancement factor for USn/sub 3/ is even larger and NpSN/sub 3/ is indeed predicted to go magnetic. We present here fully relativistic SCF calculations for these materials and discuss the relation between our results and what is known experimentally.
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