First principles study on elastic properties and phase transition of NpN

Shibata, Hiroki; Tsuru, Tomohito; Hirata, Masaru; Kaji, Yoshiyuki

doi:10.1016/j.jnucmat.2010.04.006

Cited by 11 publications

(8 citation statements)

References 32 publications

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“…The obtained equilibrium lattice constant (0.48931 nm) at 298 K was in good agreement with the experimental values of 0.48956 nm [24], 0.48968 nm [25], 0.4897 nm [20], 0.48979 nm [19], and 0.48987 nm [26] within a difference of 1%. The lattice constant also agreed with the value calculated considering the spin-orbit coupling (SOC) effect [27]. It was found that in the temperature…”

Section: Thermal and Mechanical Properties Of Npnsupporting

confidence: 83%

“…The theoretical values were a little smaller than the experimental values for UN [29,30]. In previous work, it was reported that the bulk modulus becomes slightly larger when the SOC effect is introduced [27]. Moreover, in general, an error of around 10% for the bulk modulus is inherent in first principles calculations of solids.…”

mentioning

confidence: 70%

“…First, the influence of the SOC effect on the specific heat capacity is discussed briefly in terms of the contribution of the lattice dilatation term. The ratio of the bulk modulus calculated with SOC [27] to that calculated without SOC was about 1.14 at 0 K. This ratio was assumed to be the same for all temperatures in the range of 0-1500 K. The difference between the contributions of the lattice dilatation to the specific heat capacity calculated with SOC and without SOC was smaller than the calculated value at 1500 K, that is, 0.95 J mol -1 K -1 . Therefore, it was considered that the influence of the SOC effect on the specific heat capacity is comparably small.…”

Section: Specific Heat Capacity Of Npnmentioning

confidence: 99%

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Thermodynamic properties of neptunium nitride: a first principles study

Shibata

Tsuru

Nishi

et al. 2012

Journal of Nuclear Science and Technology

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The thermal and mechanical properties of neptunium nitride (NpN) were investigated by first principles calculations. From the Helmholtz free energy equilibrium lattice constants, thermal expansion coefficients, bulk moduli and specific heat capacities were calculated for temperatures up to 1500 K. The electronic specific heat capacity was also calculated from the electronic density of states at the Fermi energy. The obtained specific heat capacity reproduced the experimental data well. It was thus clarified that the specific heat capacity of NpN consists of the lattice and electronic specific heat capacities and the contribution of the lattice dilatation to the specific heat capacity.

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Section: Thermal and Mechanical Properties Of Npnsupporting

confidence: 83%

mentioning

confidence: 70%

Section: Specific Heat Capacity Of Npnmentioning

confidence: 99%

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Thermodynamic properties of neptunium nitride: a first principles study

Shibata

Tsuru

Nishi

et al. 2012

Journal of Nuclear Science and Technology

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“…[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%

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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“…It is also worth mentioning that the first-principles calculations on actinide nitride compounds continue attracting great attention, due to improved methods and increasing interest for the fast breeder reactors and for the issues of transmutation of plutonium and minor actinides. Basic bulk properties of actinide nitrides were considered in a few recent studies [17][18][19], with emphasis on elastic and magnetic properties. The first electronic structure simulations on the perfect UN(001) surface and its reactivity towards the molecular and atomic oxygen were performed only recently [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Ab initio modeling of oxygen impurity atom incorporation into uranium mononitride surface and sub-surface vacancies

Bocharov¹,

Gryaznov²,

Zhukovskii³

et al. 2011

Journal of Nuclear Materials

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The incorporation of oxygen atoms has been simulated into either nitrogen or uranium vacancy at the UN(001) surface, sub-surface or central layers. For calculations on the corresponding slab models both the relativistic pseudopotentials and the method of projector augmented-waves (PAW) as implemented in the VASP computer code have been used. The energies of O atom incorporation and solution within the defective UN surface have been calculated and discussed. For different configurations of oxygen ions at vacancies within the UN(001) slab, the calculated density of states and electronic charge re-distribution was analyzed. Considerable energetic preference of O atom incorporation into the N-vacancy as compared to U-vacancy indicates that the observed oxidation of UN is determined mainly by the interaction of oxygen atoms with the surface and sub-surface N vacancies resulting in their capture by the vacancies and formation of O-U bonds with the nearest uranium atoms.

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First principles study on elastic properties and phase transition of NpN

Cited by 11 publications

References 32 publications

Thermodynamic properties of neptunium nitride: a first principles study

Thermodynamic properties of neptunium nitride: a first principles study

GGA+U studies of the early actinide mononitrides and dinitrides

Ab initio modeling of oxygen impurity atom incorporation into uranium mononitride surface and sub-surface vacancies

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