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Title: Comment on “Correlation and relativistic effects in U metal and U-Zr alloy: Validation of ab initio approaches”

In a recent paper, Xie et al. [Phys. Rev. B 88, 235128 (2013)], report that the density-functional theory (DFT) with the so-called DFT plus Hubbard U (DFT+U) modification improves energetics, volumes, and formation enthalpies over the standard form of DFT for uranium metal and U-Zr alloys. Also, spin-orbit coupling (SOC) was argued to advance the aforementioned properties in these systems. We demonstrate, contrarily, that neither the Hubbard U approach nor SOC is necessary for a correct description of uranium metal and U-Zr alloys. We further illustrate that the combination of DFT+U and SOC in the projector augmented-wave calculations by Xie et al. results in unrealistically large volume expansions, particularly for γ-U, in stark contrast to all previous calculations for elemental uranium. This in turn may also explain why the DFT+U with SOC model predicts negative enthalpy of mixing in the U-Zr alloy system contradicting conventional DFT as well as one of the main features of the experimental U-Zr phase diagram. The assertion by Xie et al. that DFT+U is an improvement over DFT for these systems is illustrated to be incorrect.
Authors:
 [1] ;  [1] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
OSTI Identifier:
1165820
DOE Contract Number:
AC52-07NA27344; 12-SI-008
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 90; Journal Issue: 15
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY