A first-principles investigation of point defect structure and energetics in ThO2

被引:5
作者
Singh, Maniesha [1 ]
Kumagai, Tomohisa [2 ]
El-Azab, Anter [3 ]
机构
[1] Purdue Univ, Sch Nucl Engn, W Lafayette, IN 47907 USA
[2] Cent Res Inst Elect Power Ind, Energy Transformat Res Lab, Yokosuka, Kanagawa 2400196, Japan
[3] Purdue Univ, Sch Mat Engn, W Lafayette, IN 47907 USA
关键词
URANIUM-DIOXIDE; STABILITY; DYNAMICS; BEHAVIOR; CRYSTAL;
D O I
10.1063/5.0087369
中图分类号
O59 [应用物理学];
学科分类号
摘要
The structure and energetics of charged point defects in thorium dioxide (ThO2) have been investigated using the density functional theory (DFT) and phonon simulations. DFT simulations were performed under both zero-pressure and constant volume conditions. Termed as the free volume change of the point defects, the change in volume of the supercell has been computed in the zero-pressure case. Supercell expansion was observed with the increase of the (nominal) charge state of anion (O) interstitials and cation (Th) vacancies from neutral to its maximum. On the contrary, contraction of the supercell has been observed with anion vacancies and cation interstitials as the defect charge increases. The supercell volume change with respect to the charge state has been correlated with the resulting defect energetics. It has been observed that, as the defect charge increased, the internal energy and entropy of defect formation of the cation vacancies and anion interstitials were found to increase, while that of the cation interstitials and anion vacancies decreased. The temperature dependence of internal energy and entropy has also been examined. It was found that, as the temperature increases, the internal energies of the formation of cation vacancies and anion interstitials decrease, while those of the cation interstitials and anion vacancies increase. An opposite observation is seen for the entropies of formation defects when above room temperatures. Published under an exclusive license by AIP Publishing.
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页数:14
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