Crystal-structure stabilities and electronic structure for the light actinides Th, Pa, and U

Journal Article · Mon Jun 15 00:00:00 EDT 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.13879· OSTI ID:7111511

Wills, J M; Eriksson, O ^[1]

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1. Center for Materials Science and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

The crystal-structure stabilities, equilibrium volumes, and bulk moduli (at {ital T}=0) of the light actinides Th, Pa, and U, have been calculated by means of full-potential, total-energy band-structure calculations. The total energies of the three elements were calculated as a function of volume in the three experimentally observed crystal structures: fcc, bct, and orthorhombic ({alpha}-U). Our calculations reproduce the experimentally observed crystal structures, as well as the equilibrium volumes and bulk moduli (the bulk modulus of Pa being an exception). Other calculated ground-state properties are also in good agreement with experiment, e.g., crystal-structure parameters ({ital c}/{ital a} ratio and positional parameters). On the basis of our results, we argue that the 5{ital f} electrons are participating in the chemical bonds, and that they have a large influence on the crystal structure. The equilibrium volumes of hypothetical fcc structures are found to show increasing deviations from the volumes obtained in the true crystal structures, as the 5{ital f} band becomes filled. Also, these fully relativistic calculations (assuming a fcc structure) show a smaller volume for Pu than for Np, in contrast to the experimental finding. We therefore propose that the anomalous volume of {alpha}-Pu is associated with its very unusual crystal structure, rather than with relativistic effects. Detailed information from the calculations is presented, such as the density of states, charge-density contour plots, and orbital occupation numbers.

• OSTI ID: 7111511
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 45:24; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
PROTACTINIUM
CRYSTAL STRUCTURE
ELECTRONIC STRUCTURE
THORIUM
URANIUM-ALPHA
CRYSTAL-PHASE TRANSFORMATIONS
ELASTICITY
FCC LATTICES
ORTHORHOMBIC LATTICES
ACTINIDES
CRYSTAL LATTICES
CUBIC LATTICES
ELEMENTS
MECHANICAL PROPERTIES
METALS
PHASE TRANSFORMATIONS
TENSILE PROPERTIES
URANIUM
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties