Evaluation of melting point of UO2 by molecular dynamics simulation

Arima, Takahiro; Idemitsu, Kazuya; Inagaki, Yoshiyuki; Tsujita, Yuichi; Kinoshita, Motoyasu; Yakub, E. S.

doi:10.1016/j.jnucmat.2009.01.020

Cited by 45 publications

(33 citation statements)

References 27 publications

(53 reference statements)

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“…After being constructed, the simulation cell was equilibrated at 1800 K (about 0.6 T m ; T m is about 3100 K suggested by experiments [1], or about 3325 K by the Basak potential [25]) until the total potential energy converges, and then cooled down to 300 K for deformation simulations. During deformation, the system temperature was kept at 300 K, with the temperature controlled using the Nose-Hoover thermostat [26,27].…”

Section: Methodsmentioning

confidence: 99%

Crack tip plasticity in single crystal UO2: Atomistic simulations

Zhang

Liu

Millett

et al. 2012

Journal of Nuclear Materials

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Section: Methodsmentioning

confidence: 99%

Crack tip plasticity in single crystal UO2: Atomistic simulations

Zhang

Liu

Millett

et al. 2012

Journal of Nuclear Materials

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“…Experimental results from Refs. [61] and [62] as well as the MD results from [63] are also plotted. We observe a good agreement of the calculated lattice parameters with respect to the experiments in the low-temperature domain.…”

Section: Thermodynamic Properties and P − T Phase Diagrammentioning

confidence: 99%

Phonon spectrum, thermodynamic properties, and pressure-temperature phase diagram of uranium dioxide

et al. 2013

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We present a study of the structural phase transition and the mechanical and thermodynamic properties of UO2 by means of the local density approximation (LDA)+U approach. A phase transition pressure of 40 GPa is obtained from theory at 0 K, and agrees well with the experimental value of 42 GPa. The pressure-induced enhancements of elastic constants, elastic moduli, elastic wave velocities, and Debye temperature of the ground-state fluorite phase are predicted. The phonon spectra of both the ground state fluorite structure and high pressure cotunnite structure calculated by the supercell approach show that the cotunnite structure is dynamically unstable under ambient pressure. Based on the imaginary mode along the Γ−X direction and soft phonon mode along the Γ−Z direction, a transition path from cotunnite to fluorite has been identified. We calculate the lattice vibrational energy in the quasiharmonic approximation using both first-principles phonon density of state and the Debye model. The calculated temperature dependence of lattice parameter, entropy, and specific heat agrees well with experimental observations in the low temperature domain. The difference of the Gibbs free energy between the two phases of UO2 has predicted a boundary in the pressure-temperature phase diagram. The solid-liquid boundary is approximated by an empirical equation using our calculated elastic constants.

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“…Clearly, these are physically meaningless temperatures, as urania melts at temperatures just above 3000 K [30]. However, even with the advantages provided by okMC, we are unable to simulate long enough times at operating temperatures to see diffusive behavior.…”

Section: R5 Tiltmentioning

confidence: 98%

Uranium vacancy mobility at the Σ5 symmetric tilt and Σ5 twist grain boundaries in UO2

Uberuaga

Andersson

2015

Computational Materials Science

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a b s t r a c tIonic transport at grain boundaries in oxides dictates a number of important phenomena, from ionic conductivity to sintering to creep. For nuclear fuels, it also influences fission gas bubble nucleation and growth. Here, using a combination of atomistic calculations and object kinetic Monte Carlo (okMC) simulations, we examine the kinetic pathways associated with uranium vacancies at two model grain boundaries in UO 2 . The barriers for vacancy motion were calculated using the nudged elastic band method at all uranium sites at each grain boundary and were used as the basis of the okMC simulations. For both boundaries considered -a simple tilt and a simple twist boundary -the mobility of uranium vacancies is significantly higher than in the bulk. For the tilt boundary, there is clearly preferred migration along the tilt axis as opposed to in the perpendicular direction while, for the twist boundary, migration is essentially isotropic within the boundary plane. These results show that cation defect mobility in fluorite-structured materials is enhanced at certain types of grain boundaries and is dependent on the boundary structure with the tilt boundary exhibiting higher rates of migration than the twist boundary.

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Evaluation of melting point of UO2 by molecular dynamics simulation

Cited by 45 publications

References 27 publications

Crack tip plasticity in single crystal UO2: Atomistic simulations

Crack tip plasticity in single crystal UO2: Atomistic simulations

Phonon spectrum, thermodynamic properties, and pressure-temperature phase diagram of uranium dioxide

Uranium vacancy mobility at the Σ5 symmetric tilt and Σ5 twist grain boundaries in UO2

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