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Magnetic properties and electronic structure of the actinide systems UAl/sub 2/, NpAl/sub 2/, and PuAl/sub 2/

Description: 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/.
Date: January 1, 1985
Creator: Albers, R.C.; Boring, A.M. & Koelling, D.D.
Partner: UNT Libraries Government Documents Department

Effects of B and S on Ni3Al grain boundaries

Description: This report describes the procedure used to fit embedded atom style potentials to the pure elements Ni, Al, B and S and the cross potentials necessary for treating alloys and segregants. Grain boundary simulations, and results from molecular statics simulations using the potentials for B and S, and their cross potentials with Ni and Al, which was fit from electronic band structure calculations, are included. 21 refs., 1 fig., 3 tabs. (JL)
Date: January 1, 1988
Creator: Voter, A.F.; Chen, S.P.; Albers, R.C.; Boring, A.M. & Hay, P.J.
Partner: UNT Libraries Government Documents Department

Theoretical studies of Ni/sub 3/Al and NiAl with impurities

Description: Intermetallic compound has been extensively studied because of their superior properties in strength, low creep rate, and high melting point. But most of the systems have room temperature ductility problems, like Ll/sub 2/ and B2 compounds. Both Ll/sub 2/ Ni/sub 3/Al and B2 NiAl exhibit intergranular fracture mode. Understanding grain boundaries in these materials is of particular importance since intergranular fracture limits the applicability of these otherwise promising material. In an effort trying to understand the fracture mechanism, we have used embedded atom potentials to study the properties of Ni/sub 3/Al and NiAl. We also consider the effect of boron, sulfur, and nickel segregation on the strength of grain boundaries in Ni/sub 3/Al and NiAl. 22 refs., 2 figs.
Date: January 1, 1988
Creator: Chen, S.P.; Voter, A.F.; Boring, A.M.; Albers, R.C. & Hay, P.J.
Partner: UNT Libraries Government Documents Department

Band structure of UO/sub 2/: an angle resolved and resonant photoemission study

Description: A detailed study of angle resolved photoemission of UO/sub 2/ <100> in the normal emission configuration is presented. The results are compared to a semirelativistic LAPW band calculation with the actual calculated empty bands used in the data reduction. Excellent agreement is found with calculations both for filled states as well as critical points in the empty states with no adjustment of bands. f-p hybridization is found at the leading edge of the valence band and not at the bottom of the valence band. p-d hybridization is found throughout the valence bands.
Date: October 1, 1985
Creator: Arko, A.J.; Koelling, D.D.; Boring, A.M.; Ellis, W.P. & Cox, L.E.
Partner: UNT Libraries Government Documents Department

Self-consistent electronic structure of alpha-phase Hume-Rothery electron compound alloys Cu/sub c/Zn/sub 1-c/, Cu/sub c/Ga/sub 1-c/, and Cu/sub c/Ge/sub 1-c/

Description: We have performed charge self-consistent electronic structure calculations for the ..cap alpha..-phase Hume-Rothery electron compound alloys Cu/sub c/Zn/sub 1-c/, Cu/sub c/Ga/sub 1-c/, and Cu/sub c/Ge/sub 1-c/ having electron to atom ratios 1:1, 1:2, and 1:3 for each alloy series. The calculations are based on the self-consistent-field Korringa-Kohn-Rostoker coherent-potential approximation (KKR-CPA). We show results for the densities of states and Fermi surface of these alloys; the behavior of these quantities is quite different from that predicted on the basis of the rigid band model. We also show results for the ground state properties of the Cu/sub c/Zn/sub 1-c/ alloys that were obtained on the basis of a recent generalization of the density functional theory to random alloys. The theory provides a basis for understanding the concentration variation of the lattice parameter (Vegards' Law) of Cu/sub c/Zn/sub 1-c/ alloys at the microscopic quantum mechanical level.
Date: January 1, 1985
Creator: Stocks, G.M.; Boring, A.M.; Nicholson, D.M.; Pinski, F.J.; Johnson, D.D.; Faulkner, J.S. et al.
Partner: UNT Libraries Government Documents Department

Fermi surface and effective masses for the heavy-electron superconductor UPt sub 3

Description: Local-density-approximation (LDA) calculations for the Fermi-surface extremal cross-sectional areas of UPt{sub 3} are presented and compared to deHaas-van Alphen experiments of Taillefer et al. The topology of the calculated surfaces is in excellent agreement with experiment and allows a determination of the directional dependence of the anisotropic mass-renormalization factor. The source of this renormalization is briefly discussed. 12 refs., 4 figs., 2 tabs.
Date: October 1, 1987
Creator: Norman, M.R.; Albers, R.C.; Boring, A.M.; Christensen, N.E. (Argonne National Lab., IL (USA); Los Alamos National Lab., NM (USA) & Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany, F.R.))
Partner: UNT Libraries Government Documents Department

Magnetism and bonding in actinide and rare earth systems

Description: The importance of including all of Hund's rules in self consistent electronic structure calculations is pointed out. We present a scheme that accounts for the interactions that lead to these rules, and we give examples of when these interactions become important. Calculated ground state properties (chemical bonding, magnetic moment, magnetic form factor) of actinide and rare earth systems are found to agree better with experiment when all Hund's rules are accounted for. On the other hand, for Fe, Co and Ni we find that it is a reasonable approximation to neglect Hund's second and third rule. 20 refs., 5 figs., 3 tabs.
Date: January 1, 1990
Creator: Eriksson, O.; Albers, R.C.; Boring, A.M. (Los Alamos National Lab., NM (USA)); Brooks, M.S.S. (Commission of the European Communities, Karlsruhe (Germany, F.R.). European Inst. for Transuranium Elements) & Johansson, B. (Uppsala Univ. (Sweden). Inst. of Physics)
Partner: UNT Libraries Government Documents Department