The thermodynamic properties of β-UO3 and γ-UO3

Cordfunke, E.H.P.; Westrum, Edgar F.

doi:10.1016/0040-6031(88)87031-x

Cited by 18 publications

(24 citation statements)

References 18 publications

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“…The computed thermodynamic properties of uranium trioxide are also in excellent agreement with the experimental data of Cordfunke and Westrum [143] in the full range of temperatures considered 0-1000 K. The differences in the specific heat, entropy, and Gibbs free energy functions are 3.9, 1.8, and 0.1% at 100 K and 6.1, 3.6, and 3.5% at 1000 K. The comparison reveals that the low temperature calculated thermodynamic data are also very accurate. It must be emphasized that while the experimental isobaric heat capacity function of gamma uranium trioxide at 1000 K is above the asymptotic Dulong-Petit limit, our computed function satisfies properly the requirement of being below this limit [100].…”

Section: Density Functional Theorysupporting

confidence: 79%

“…The calculated isobaric specific heat, entropy, and Gibbs free energy functions of rutherfordine, gamma uranium trioxide, and metaschoepite are displayed in Figure 2, where they are compared with the experimental functions of Hemingway [37], Cordfunke and Westrum [143], and Barin [12], respectively. For rutherfordine, the computed thermodynamic functions are compared with those of Hemingway [37] in the temperature range of 298-700 K, and as it can be appreciated, the calculated and experimental curves are nearly parallel.…”

Section: Thermodynamic Propertiesmentioning

confidence: 99%

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The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

Ruiz¹

2019

Density Functional Theory

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With the advent of increased computer capacities, improved computational resources, and easier access to large-scale computer facilities, the use of density functional theory methods has become nowadays a frequently used and highly successful approach for the research of solid-state materials. However, the study of solid materials containing heavy elements as lanthanide and actinide elements is very complex due to the large size of these atoms and the requirement of including relativistic effects. These features impose the availability of large computational resources and the use of high quality relativistic pseudopotentials for the description of the electrons localized in the inner shells of these atoms. The important case of the description of uranyl-containing materials and their properties has been faced recently. The study of these materials is very important in the energetic and environmental disciplines. Uranyl-containing materials are fundamental components of the paragenetic sequence of secondary phases that results from the weathering of uraninite ore deposits and are also prominent phases appearing from the alteration of the spent nuclear fuel. The development of a new norm-conserving relativistic pseudopotential for uranium, the use of energy density functionals specific for solids, and the inclusion of empirical dispersion corrections for describing the long-range interactions present in the structures of these materials have allowed the study of the properties of these materials with an unprecedented accuracy level. This feature is very relevant because these methods provide a safe, accurate, and cheap manner of obtaining these properties for uranium-containing materials which are highly radiotoxic, and their experimental studies demand a careful handling of the samples used. In this work, the results of recent applications of theoretical solid state methods based on density functional theory using plane waves and pseudopotentials to the determination of the thermodynamic properties and stability of uranyl-containing materials are reviewed. The knowledge of these thermodynamic properties is indispensable to model the dynamical behavior of nuclear materials under diverse geochemical conditions. The theoretical methods provide

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Section: Density Functional Theorysupporting

confidence: 79%

Section: Thermodynamic Propertiesmentioning

confidence: 99%

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

Ruiz¹

2019

Density Functional Theory

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“…The computed low-and high-temperature (0-300 K and 300-1000 K) thermodynamic properties, including heat capacity, entropy, enthalpy and free energy, are in excellent agreement with the experimental ones of Cordfunke and Westrum. 38 At 298.15 K, the computed values of these properties differ from the experimental values by 5.3, 3.3, 3.9 and 2.6 %, respectively. While experimental isobaric heat capacity function at 1000 K is above the Dulong-Petit limit, the computed function satisfies properly the requirement of being below the limit.…”

Section: Discussionmentioning

confidence: 70%

“…The value obtained for the isobaric specific heat at zero pressure and 298.15 K is Cp=77.36 J/(K•mol), which may be compared with the experimental value of Cordfunke and Westrum38 of 81.67 J/(K•mol). The agreement is very good, our value being lower than the experimental value by about 5.3%.…”

mentioning

confidence: 68%

Density Functional Theory Study of the Thermodynamic and Raman Vibrational Properties of γ-UO₃ Polymorph

et al. 2017

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Gamma uranium trioxide, γ-UO3, is one of the most important polymorphs in uranium trioxide system which is common throughout the nuclear fuel cycle and used industrially in the reprocessing of nuclear fuel and uranium enrichment. In this work, a detailed theoretical solid-state density functional theory study of this material was carried out. The computed lattice parameters, bond lengths, bond angles and X-Ray powder pattern were found in very good agreement with their experimental counterparts determined by X-Ray diffraction. The equation of state of γ-UO3 was obtained and, therefore, the values of the bulk modulus and its derivatives, for which there are not experimental data to compare with, were predicted. The computed bulk modulus differs from that of a previous density functional theory calculation by only 4.4%. The thermodynamic properties of this material, including heat capacity, entropy, enthalpy, free energy and Debye temperature were also determined as a function of temperature in the range 0-1000 K. The computed low-and high-temperature thermodynamic functions are in excellent agreement with the experimental ones determined from calorimetric measurements. At ambient temperature, the computed values of heat capacity, entropy, enthalpy and free energy differ from the experimental values by 5.3, 3.3, 3.9 and 2.6%, respectively. Finally, the Raman spectrum was determined and compared with the experimental one and was found to be in good agreement. A normal mode analysis of the theoretical spectra was carried out and used in order to resolve the uncertainty of the assignment in the observed Raman bands. The assignment permits to attribute the different bands to vibrations localized in the different distorted octahedra associated to the two non-equivalent uranium atom types present in the structure of γ-UO3.

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“…In order to use this expression experimental heat capacity around 10 K is required. However, present study measures heat capacity above 126 K. The heat capacity data on BaU 2 O 7 (s), Ba 2 U 3 O 11 (s), Ba 2.875 UO 5.875 (s) and Ba 3 UO 6 (s) have not been reported in the literature in the temperature range 0-127 K. However, heat capacity for BaUO 4 (s) [14] has been reported in the temperature range 0.7-292 K and that for BaO(s) [25] and UO 3 (s) [26] …”

Section: Calculations Of S O M (29815 K) Of Stoichiometric Oxides Ofmentioning

confidence: 76%

Calorimetric investigations on stoichiometric barium and uranium oxides

Dash

Singh

2010

Journal of Nuclear Materials

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The thermodynamic properties of β-UO3 and γ-UO3

Abstract: Heat capacitiesof carefully characterized samples of p-UO, and y-UO, have been measured from 5 to 350 K using an adiabatic calorimeter, and from 350 to 700 K by enthalpy increment drop calorimetry. Values for the thermodynamic properties at 298.

Cited by 18 publications

References 18 publications

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

Density Functional Theory Study of the Thermodynamic and Raman Vibrational Properties of γ-UO₃ Polymorph

Calorimetric investigations on stoichiometric barium and uranium oxides

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The thermodynamic properties of β-UO3 and γ-UO3

Abstract: Heat capacitiesof carefully characterized samples of p-UO, and y-UO, have been measured from 5 to 350 K using an adiabatic calorimeter, and from 350 to 700 K by enthalpy increment drop calorimetry. Values for the thermodynamic properties at 298.

Cited by 18 publications

References 18 publications

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

The Application of Periodic Density Functional Theory to the Study of Uranyl-Containing Materials: Thermodynamic Properties and Stability

Density Functional Theory Study of the Thermodynamic and Raman Vibrational Properties of γ-UO3 Polymorph

Calorimetric investigations on stoichiometric barium and uranium oxides

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Density Functional Theory Study of the Thermodynamic and Raman Vibrational Properties of γ-UO₃ Polymorph