Lattice Expansion By Intrinsic Defects in Uranium By Molecular Dynamics Simulation

Abstract

A re-formulated and re-parameterized interatomic potential for uranium metal in the Charge-Optimized Many-Body (COMB) formalism is presented. Most physical properties of the orthorhombic α and bcc γ phases are accurately reproduced. In particular, this potential can reproduce the negative thermal expansion of the b axis in α-U while keeping this phase as the most stable phase at low temperatures, in accord with experiment. Most of the volume expansion in α-U by intrinsic defects is shown to come from the b axis, due to the formation of prismatic loops normal to this direction. Glide dislocation loops forming stacking faults are also observed. Structures of both loop types are analyzed. An expansion simulation is conducted and the results are verified by using the Norgett-Robinson-Torrens model. Rather than forming extended defect structures as in α-U, the γ phase forms only isolated defects and thus results in a much smaller and isotropic expansion.

Department(s)

Physics

Research Center/Lab(s)

Center for High Performance Computing Research

Keywords and Phrases

Defect Structures; Defects; Expansion; Stacking Faults; Thermal Expansion; Uranium; Glide Dislocations; Interatomic Potential; Intrinsic Defects; Isotropic Expansion; Lattice Expansion; Molecular Dynamics Simulations; Negative Thermal Expansion; Volume Expansion; Molecular Dynamics

International Standard Serial Number (ISSN)

0022-3115

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2016 Elsevier B.V., All rights reserved.

Publication Date

01 Jul 2016

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