skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Atomic-volume variations of (alpha)-Pu alloyed with Al, Ga, and Am from first-principles theory

Abstract

First-principles methods are employed to calculate the ground-state atomic densities (or volumes) of {alpha}-Pu alloyed with Al, Ga, and Am. Three configurations for the alloying atom are considered. (1) It is located at the most open and energetically most favorably site. (2) It is located in the least open site. (3) It is randomly distributed within the {alpha}-Pu matrix. When alloyed with Al or Ga, {alpha}-Pu behaves similarly, it expands considerably for configurations (2) and (3), while for (1) only small changes of the density occurs. Interestingly, for Am the alloying effects are quite different from that of Al and Ga. Small expansion is noted for the ordered configurations (1) and (2), whereas for the disordered (3), only insignificant changes of the density take place. The bonding character is thus differently influenced in Pu by the addition of Al and Ga on one hand and Am on the other. This is consistent with the view that Al and Ga stabilize the {delta} over the {alpha} phase in Pu by a different mechanism than Am, as has been discussed in recent publications.

Authors:
; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
940474
Report Number(s):
UCRL-JRNL-227225
TRN: US0807140
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: JOURNAL OF COMPUTER-AIDED MATERIALS DESIGN , vol. 14, no. 3, October 1, 2007, pp. 349-355; Journal Volume: 14; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; BONDING; METALLURGICAL EFFECTS

Citation Formats

Soderlind, P, Landa, A, and Wolfer, W G. Atomic-volume variations of (alpha)-Pu alloyed with Al, Ga, and Am from first-principles theory. United States: N. p., 2007. Web.
Soderlind, P, Landa, A, & Wolfer, W G. Atomic-volume variations of (alpha)-Pu alloyed with Al, Ga, and Am from first-principles theory. United States.
Soderlind, P, Landa, A, and Wolfer, W G. Tue . "Atomic-volume variations of (alpha)-Pu alloyed with Al, Ga, and Am from first-principles theory". United States. doi:. https://www.osti.gov/servlets/purl/940474.
@article{osti_940474,
title = {Atomic-volume variations of (alpha)-Pu alloyed with Al, Ga, and Am from first-principles theory},
author = {Soderlind, P and Landa, A and Wolfer, W G},
abstractNote = {First-principles methods are employed to calculate the ground-state atomic densities (or volumes) of {alpha}-Pu alloyed with Al, Ga, and Am. Three configurations for the alloying atom are considered. (1) It is located at the most open and energetically most favorably site. (2) It is located in the least open site. (3) It is randomly distributed within the {alpha}-Pu matrix. When alloyed with Al or Ga, {alpha}-Pu behaves similarly, it expands considerably for configurations (2) and (3), while for (1) only small changes of the density occurs. Interestingly, for Am the alloying effects are quite different from that of Al and Ga. Small expansion is noted for the ordered configurations (1) and (2), whereas for the disordered (3), only insignificant changes of the density take place. The bonding character is thus differently influenced in Pu by the addition of Al and Ga on one hand and Am on the other. This is consistent with the view that Al and Ga stabilize the {delta} over the {alpha} phase in Pu by a different mechanism than Am, as has been discussed in recent publications.},
doi = {},
journal = {JOURNAL OF COMPUTER-AIDED MATERIALS DESIGN , vol. 14, no. 3, October 1, 2007, pp. 349-355},
number = 3,
volume = 14,
place = {United States},
year = {Tue Jan 09 00:00:00 EST 2007},
month = {Tue Jan 09 00:00:00 EST 2007}
}
  • We present a newly developed self-consistent CALPHAD thermodynamic database involving Al, Am, Ga, Pu, and U. A first optimization of the slightly characterized Am-Al and completely unknown Am-Ga phase diagrams is proposed. To this end, phase diagram features as crystal structures, stoichiometric compounds, solubility limits, and melting temperatures have been studied along the U-Al → Pu-Al → Am-Al, and U-Ga → Pu-Ga → Am-Ga series, and the thermodynamic assessments involving Al and Ga alloying are compared. In addition, two distinct optimizations of the Pu-Al phase diagram are proposed to account for the low temperature and Pu-rich region controversy. We includedmore » the previously assessed thermodynamics of the other binary systems (Am-Pu, Am-U, Pu-U, and Al-Ga) in the database and is briefly described in the present work. In conclusion, predictions on phase stability of ternary and quaternary systems of interest are reported to check the consistency of the database.« less
  • Two types of global space-group optimization (GSGO) problems can be recognized in binary metallic alloys A{sub q}B{sub 1-q}: (1) configuration search problems, where the underlying crystal lattice is known and the aim is finding the most favorable decoration of the lattice by A and B atoms and (2) lattice-type search problems, where neither the lattice type nor the decorations are given and the aim is finding energetically favorable lattice vectors and atomic occupations. Here, we address the second, lattice-type search problem in binary A{sub q}B{sub 1-q} metallic alloys, where the constituent solids A and B have different lattice types. Wemore » tackle this GSGO problem using an evolutionary algorithm, where a set of crystal structures with randomly selected lattice vectors and site occupations is evolved through a sequence of generations in which a given number of structures of highest LDA energy are replaced by new ones obtained by the generational operations of mutation or mating. Each new structure is locally relaxed to the nearest total-energy minimum by using the ab initio atomic forces and stresses. We applied this first-principles evolutionary GSGO scheme to metallic alloy systems where the nature of the intermediate A-B compounds is difficult to guess either because pure A and pure B have different lattice types and the (1) intermediate compound has the structure of one end-point (Al{sub 3}Sc, AlSc{sub 3}, CdPt{sub 3}), or (2) none of them (CuPd, AlSc), or (3) when the intermediate compound has lattice sites belonging simultaneously to a few types (fcc, bcc) (PdTi{sub 3}). The method found the correct structures, L1{sub 2} type for Al{sub 3}Sc, D0{sub 19} type for AlSc3, 'CdPt{sub 3}' type for CdPt{sub 3}, B2 type for CuPd and AlSc, and A15 type for PdTi{sub 3}. However, in such stochastic methods, success is not guaranteed, since many independently started evolutionary sequences produce at the end different final structures: one has to select the lowest-energy result from a set of such independently started sequences. Interestingly, we also predict a hitherto unknown (P 2/m) structure of the hard compound IrN{sub 2} with energy lower than all previous predictions.« less