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Title: Structure determination and stability for Pa-Si, Np-Si and U-X-Si (X = Mo, Th, Np) phases from first-principles

Abstract

Density functional theory (DFT) calculations are performed for Pa-Si, Np-Si and uranium-based ternary silicide phases. Structure prediction calculations are used to search for competing phases in these systems. Results using the generalized gradient approximation (GGA), on-site Coulomb correction (GGA + U) and van der Waals interactions are presented. All Pa-Si compounds reported here are structurally analogous to those found in other actinide silicide systems. The electronic structure of Pa 3Si 2 shows the f-orbital electrons are largely unoccupied, which is in contrast to calculations for Np 3Si 2. For the Np-Si system, predicted stable structures using GGA differ from the experimentally observed structures, which, however, are energetically preferred in results using the GGA + U method. Structure searches for U 2MoSi, U 2ThSi 2 and UNpSi reveal dynamically stable ternary compounds. The phonon dispersion curves, elastic constants and electronic density of states for the various phases are compared to those from previous DFT calculations for U-Si phases.

Authors:
 [1]; ORCiD logo [2];  [3]
  1. Univ. of South Carolina, Columbia, SC (United States). Dept. of Mechanical Engineering
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Univ. of South Carolina, Columbia, SC (United States). Dept. of Mechanical Engineering
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1458940
Alternate Identifier(s):
OSTI ID: 1359435; OSTI ID: 1458931
Report Number(s):
LA-UR-16-22383; LA-UR-16-21444
Journal ID: ISSN 0022-3115; TRN: US1901530
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 479; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS

Citation Formats

Noordhoek, Mark J., Andersson, Anders David Ragnar, and Besmann, Theodore M. Structure determination and stability for Pa-Si, Np-Si and U-X-Si (X = Mo, Th, Np) phases from first-principles. United States: N. p., 2016. Web. doi:10.1016/j.jnucmat.2016.07.058.
Noordhoek, Mark J., Andersson, Anders David Ragnar, & Besmann, Theodore M. Structure determination and stability for Pa-Si, Np-Si and U-X-Si (X = Mo, Th, Np) phases from first-principles. United States. doi:10.1016/j.jnucmat.2016.07.058.
Noordhoek, Mark J., Andersson, Anders David Ragnar, and Besmann, Theodore M. Sat . "Structure determination and stability for Pa-Si, Np-Si and U-X-Si (X = Mo, Th, Np) phases from first-principles". United States. doi:10.1016/j.jnucmat.2016.07.058. https://www.osti.gov/servlets/purl/1458940.
@article{osti_1458940,
title = {Structure determination and stability for Pa-Si, Np-Si and U-X-Si (X = Mo, Th, Np) phases from first-principles},
author = {Noordhoek, Mark J. and Andersson, Anders David Ragnar and Besmann, Theodore M.},
abstractNote = {Density functional theory (DFT) calculations are performed for Pa-Si, Np-Si and uranium-based ternary silicide phases. Structure prediction calculations are used to search for competing phases in these systems. Results using the generalized gradient approximation (GGA), on-site Coulomb correction (GGA + U) and van der Waals interactions are presented. All Pa-Si compounds reported here are structurally analogous to those found in other actinide silicide systems. The electronic structure of Pa3Si2 shows the f-orbital electrons are largely unoccupied, which is in contrast to calculations for Np3Si2. For the Np-Si system, predicted stable structures using GGA differ from the experimentally observed structures, which, however, are energetically preferred in results using the GGA + U method. Structure searches for U2MoSi, U2ThSi2 and UNpSi reveal dynamically stable ternary compounds. The phonon dispersion curves, elastic constants and electronic density of states for the various phases are compared to those from previous DFT calculations for U-Si phases.},
doi = {10.1016/j.jnucmat.2016.07.058},
journal = {Journal of Nuclear Materials},
number = C,
volume = 479,
place = {United States},
year = {2016},
month = {10}
}

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