Electronic structures, mechanical and thermodynamic properties of ThN from first-principles calculations

Lu, Yuhao; Li, Dafang; Wang, Bao-Tian; Li, Rongwu; Zhang, Ping

doi:10.1016/j.jnucmat.2010.11.007

Cited by 37 publications

(17 citation statements)

References 27 publications

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“…In order to evaluate the Poisson ′ s ratio ν, we calculated the three independent elastic constants C 11 , C 12 and C 44 of ThO 2 . The calculation methods are the same as in our previous studies [35,46,47]. The obtained elastic constants for ThO 2 are C 11 =351.2 GPa, C 12 =106.9 GPa, and C 44 =74.1 GPa, which are in accordance with experimentally measured values of C 11 =367 GPa, C 12 =106 GPa, and C 44 =79 GPa [48].…”

Section: A Structure and Elastic Constants Of Tho2supporting

confidence: 82%

Thermodynamic properties and structural stability of thorium dioxide

Lu¹,

Yang²,

P³

2012

J. Phys.: Condens. Matter

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Using density functional theory (DFT) calculations, we have systematically investigated the thermodynamic properties and structural stabilities of thorium dioxide (ThO2). Based on the calculated phonon dispersion curves, we calculate the thermal expansion coefficient, bulk modulus, and heat capacities at different temperatures for ThO2 under the quasi-harmonic approximation. All the results are in good agreement with corresponding experiments proving the validity of our methods. Our theoretical studies can help people more clearly understand the thermodynamic behaviors of ThO2 at different temperatures. In addition, we have also studied possible defect formations and diffusion behaviors of helium in ThO2, to discuss its structural stability. It is found that in intrinsic ThO2 without any Fermi energy shifts, the interstitial Th 4+ i defect other than oxygen or thorium vacancies, interstitial oxygen, and any kinds of Frenkel pairs, is most probable to form with an energy release of 1.74 eV. However, after upshifting the Fermi energy, the formation of the other defects also becomes possible. For helium diffusion, we find that only through the thorium vacancy can it happen with the small energy barrier of 0.52 eV. Otherwise, helium atoms can hardly incorporate or diffuse in ThO2. Our results indicate that people should prevent upshifts of the Fermi energy of ThO2 to avoid the formation of thorium vacancies and so as to prevent helium caused damages.

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Section: A Structure and Elastic Constants Of Tho2supporting

confidence: 82%

Thermodynamic properties and structural stability of thorium dioxide

Lu¹,

Yang²,

P³

2012

J. Phys.: Condens. Matter

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“…10, an insulating character is observed for UN 2 with a GGA band gap of 0.56 eV and an increase in the band gap to 0.64 eV on the inclusion of the Hubbard U of 2 eV. This is comparable to the band gap obtained by Weck et al [23] of 0.94 eV using the AE approach and by Lu et al [8] of 0.75 eV using a Hubbard U of 4 eV. If we consider the FM structure, which is less energetically favorable, a GGA band gap of 0.73 eV and a band gap of 0.83 eV on inclusion of the Hubbard U of 2 eV (figure not presented) is obtained.…”

Section: Compoundsupporting

confidence: 81%

“…They are all positive, which indicates that the compounds are all elastically stable. The inclusion of the U parameter leads to an overall better agreement of the calculated elastic properties with other available theoretical and experimental data [41,42,22,8]. For instance, the experimentally determined bulk modulus and the calculated result of our lowest energy structure in parenthesis for ThN and UN are 175 GPa [43] (178 GPa) and 193 GPa [41] (198 GPa) respectively.…”

Section: Elastic Propertiessupporting

confidence: 55%

“…[1,2,3,4,5,6,7,8,9,10,11,12] The effects of 5f-electrons in the actinide nitrides are of significant interest to both theorists and experimentalists, [13,14,15] because exotic properties often arise from the strong electron-electron interactions paving the way for interesting physics and novel applications. The actinide metals exhibit increased 5f electronic localization with increasing atomic number which has a direct bearing on the orbital overlap and electronic band structure of these systems.…”

Section: Introductionmentioning

confidence: 99%

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GGA+U studies of the early actinide mononitrides and dinitrides

Obodo

Chetty

2013

Journal of Nuclear Materials

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Abstract. We present a detailed comparative study of the electronic and mechanical properties of the early actinide mononitrides and dinitrides within the framework of the Perdew-Burke-Ernzerhof generalized gradient approximation (GGA [PBE]) and GGA + U implementations of density functional theory with the inclusion of spin-orbit coupling. The dependence of selected observables of these materials on the effective U-parameter is investigated in detail. The properties include the lattice constant, bulk modulus, charge density distribution, hybridization of the atomic orbitals, energy of formation and the lattice dynamics. The inclusion of the Hubbard U parameter results in a proper description of the 5f electrons, and is subsequently used in the determination of the structural and electronic properties of these compounds. The mononitrides and dinitrides of the early actinides are metallic except for UN 2 , which is a semiconductor. These actinide nitrides are non-magnetic with the exception of UN, NpN, PuN, NpN 2 and PuN 2 that are magnetic systems with orbital-dependent magnetic moments oriented in the z-axis. We observed that ThN 2 is elastically unstable to isotropic pressure. We discovered that UN 2 is thermodynamically unstable, but may be stabilized by N vacancy formation.

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“…Lu et al 22 used the same method based on the elastic, valence charge density distribution and phonon dynamics to study ThN, which has been experimentally synthesized with an experimental lattice constant of 5.154 Å and bulk modulus of 175 GPa. This validates the approach used in this study.…”

Section: Methodsmentioning

confidence: 99%

A theoretical study of thorium titanium-based alloys

Obodo¹,

Chetty²

2013

Journal of Nuclear Materials

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Using theoretical quantum chemical methods, we investigate the dearth of ordered alloys involving thorium and titanium. Whereas both these elements are known to alloy very readily with various other elements, for example with oxygen, current experimental data suggests that Th and Ti do not alloy very readily with each other. In this work, we consider a variety of ordered alloys at varying stoichiometries involving these elements within the framework of density functional theory using the generalized gradient approximation for the exchange and correlation functional. By probing the energetics, electronic, phonon and elastic properties of these systems, we confirm the scarcity of ordered alloys involving Th and Ti, since for a variety of reasons many of the systems that we considered were found to be unfavorable. However, our investigations resulted in one plausible ordered structure: We propose ThTi 3 in the Cr 3 Si structure as a metastable ordered alloy.

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Electronic structures, mechanical and thermodynamic properties of ThN from first-principles calculations

Cited by 37 publications

References 27 publications

Thermodynamic properties and structural stability of thorium dioxide

Thermodynamic properties and structural stability of thorium dioxide

GGA+U studies of the early actinide mononitrides and dinitrides

A theoretical study of thorium titanium-based alloys

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