Stability mechanism of cuboctahedral clusters in UO2: First-principles calculations

Abstract

The stability mechanism of cuboctahedral clusters in nonstoichiometric uranium dioxide is investigated by first-principles LSDA+U method. Calculations reveal that the structural stability is inherited from U6O12 molecular cluster whereas the energy gain through occupying its center with an additional oxygen makes the cluster win out by competition with point oxygen interstitials. Local displacement of the center oxygen along <111> direction also leads the cluster 8-folded degeneracy and increases relatively the concentration at finite temperatures. But totally, elevation of temperature, i.e., the effect of entropy, favors point interstitial over cuboctahedral clusters.

5 pages, 3 figures

References in corpus (2)

• Point defects and clustering in uranium dioxide by LSDA+U calculations
• Structural behavior of uranium dioxide under pressure by LSDA+U calculations

Cited by in corpus (7)

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• Ab initio investigation on oxygen defect clusters in UO2+x
• First-principles study on oxidation effects in uranium oxides and high-pressure high-temperature behavior of point defects in uranium dioxide
• Self-consistent density functional calculations of the crystal field levels in lanthanide and actinide dioxides
• Theoretical assessment on the possibility of constraining point defect energetics by pseudo-phase transition pressures