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

Ruiz, Francisco Colmenero

doi:10.5772/intechopen.79558

Cited by 6 publications

(31 citation statements)

References 129 publications

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“…The results presented in the published papers [42,[53][54][55][56][57][58][59][60][61][62][63] show that the theoretical computations are an extremely powerful tool in the research of uranium-containing compounds. Once the proper relativistic norm-conserving pseudopotential has been generated [42,52], the structural information, the X-ray powder patterns, the vibrational Raman spectra and mechanical and thermodynamic properties of these substances can be determined.…”

Section: Discussionmentioning

confidence: 99%

“…Whereas our uranium atom pseudopotential includes scalar relativistic effects, the corresponding pseudopotentials used for H, C, O, Si, and Ca atoms do not include them. This pseudopotential has been used extensively in the research of uranyl-containing materials [42,[52][53][54][55][56][57][58][59][60][61][62][63].…”

Section: Methodsmentioning

confidence: 99%

“…Theoretical solid-state calculations allow a safe and complete characterization of uranylcontaining materials free of the inconveniences associated to their radiotoxicity [42,[52][53][54][55][56][57][58][59][60][61][62][63]. However, the application of these methods to the study of mineral phases containing Rare Earth Elements is difficult not only due to the complexity of these materials but also to the high level of theory needed to describe these materials [64,65].…”

Section: +mentioning

confidence: 99%

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Theoretical Studies of the Structural, Mechanical and Raman Spectroscopic Properties of Uranyl-Containing Minerals

Ruiz¹

2019

Minerals

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The incipient use of theoretical methods in the research of geomaterials reveals the great power of such methodology in the determination of the mineral properties. These methods provide a safe, accurate and cheap manner of obtaining these properties. Uranium-containing minerals are highly radiotoxic, and their experimental studies demand a careful handling of the samples used. However, theoretical methods are free of such inconveniences and may be used in the complete characterization of this type of minerals. Theoretical methods are not only a complement to the use of other experimental techniques but also a powerful predictive tool. The structural, mechanical and Raman spectroscopic properties of uranyl-containing materials, including rutherfordine soddyite, schoepite and uranophane-α, were studied by means of theoretical solid-state methods based on density functional theory using plane waves and pseudopotentials. A new norm-conserving relativistic pseudopotential for uranium atom developed in recent works was employed. These minerals are among the most important secondary phases arising from corrosion of spent nuclear fuel under the final geological disposal conditions. The computed crystal structures of these materials as well as the corresponding and X-ray powder patterns were found to be in excellent agreement with the experimental information. Therefore, the optimized structures of these minerals were employed to study the mechanical properties and stability of these minerals. These properties were obtained using the finite deformation technique. All these minerals were found to be mechanically stable since the corresponding Born stability conditions were satisfied. A large amount of relevant mechanical data were reported including bulk, Young and Shear moduli, Poisson ratios, ductility and hardness indices, anisotropy measures as well as longitudinal and transversal wave velocities. The large volume expansion and mechanical stress resulting from the corrosion of spent nuclear fuel during storage emphasize the great relevance of the mechanical information of the waste components. Finally, the computation of vibrational properties of these minerals is studied. The computed Raman spectra of these materials were found to be in good agreement with their experimental

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: +mentioning

confidence: 99%

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Theoretical Studies of the Structural, Mechanical and Raman Spectroscopic Properties of Uranyl-Containing Minerals

Ruiz¹

2019

Minerals

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“…80,24-25.72,78 The thermodynamic properties of formation and reaction will be evaluated in terms of the calculated fundamental thermodynamic properties using the methods described in the next subsections. [72][73]81…”

Section: Ii2 Fundamental Thermodynamic Propertiesmentioning

confidence: 99%

Thermodynamic, Raman Spectroscopic, and UV–Visible Optical Characterization of the Deltic, Squaric, and Croconic Cyclic Oxocarbon Acids

Colmenero

Escribano

2019

J. Phys. Chem. A

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A precise and complete thermodynamic, Raman spectroscopic and ultraviolet-visible optical characterization of the deltic, squaric and croconic cyclic oxocarbon acids is obtained using theoretical solid-state methods employing very demanding calculation parameters. The computed fundamental thermodynamic properties include the isobaric specific heat, the entropy, the enthalpy and the Gibbs free energy as a function of temperature. The calculated specific heats at 298.15 K of the deltic, squaric and croconic acids are 89.7, 111.2 and 133.2 J • mol −1 • K −1 , respectively, and the corresponding entropies are 98.3, 117.3 and 136.5 J • mol −1 • K −1 . The only value of these properties known from experimental measurements is the specific heat of the squaric acid which differs from the computed value at 315 K by about 4.9%. The calculated values of the thermodynamic properties are then used to determine the thermodynamic properties of formation of these materials in terms of the elements. As an application of the calculated thermodynamic properties of formation, the Gibbs free energies of reaction and associated reaction constants are evaluated for the reactions of thermal decomposition and complete combustion of the squaric and croconic acids and the reaction of interconversion between them. The only available experimental values of these properties, namely the enthalpies of combustion of squaric and croconic acids at room temperature, are reproduced theoretically with high accuracy. The Raman spectra of these materials are also computed using Density Functional Perturbation Theory. The analysis of the theoretical Raman spectra of these materials points out to significant differences with respect to their usual empirical assignment. Therefore, the Raman spectra of these materials is fully reassigned. Finally, the ultraviolet-visible (UV-Vis) optical properties of the deltic, squaric and croconic acids are computed. The UV-Vis absorption spectrum of the croconic acid in the spectral region 225-425 nm and the UV absorption spectrum of the squaric acid in the region 200-350 nm which had previously been measured experimentally are well reproduced. The corresponding spectrum for the deltic acid and the reflectivity, optical conductivity, dielectric, refractive index and loss optical functions of the three materials, which had never been published as far as we know, are reported as a function of the wavelength of incident radiation in the range 200-750 nm. The origin of the peaks in the absorption spectra which had not been analyzed so far is unveiled here by examining the inter-band electronic transitions in these materials.their reactions of complete combustion:and the reaction of conversion between them in the presence of carbon monoxide: (E) H 2 C 4 O 4 (cr) + CO(g) → H 2 C 5 O 5 (cr) as a function of temperature. The thermodynamic parameters of organic compounds are extraordinarily important not only in

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“…The first rigorous assignment of the Raman spectrum of an uranyl containing mineral was performed in 2016 [27] for the uranyl carbonate mineral rutherfordine. The development of a new high-quality norm conserving relativistic pseudopotential specific for uranium atom [27][28], has allowed an accurate theoretical solid-state treatment of these materials [29][30]. These theoretical studies have been used not only as a complement of the experimental techniques allowing the determination of the complete crystal structures of many uranyl containing materials [31][32][33] and the precise assignment of their Raman spectra [26,28,31,[34][35], but also as a very powerful predictive tool of their thermodynamic, mechanical and optical properties [31][32][33][34][35][36][37][38][39][40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Periodic density functional theory study of the Raman spectrum of the hydrated uranyl oxyhydroxide mineral becquerelite

2019

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Raman spectroscopy is one of the main analytic techniques used to identify uranyl-containing minerals. However, the assignment of the Raman spectra of these minerals is usually performed by using empirical arguments leading to unreliable assignments. In this paper, the Raman spectrum of the hydrated uranyl oxyhydroxide mineral becquerelite, Ca(UO 2) 6 O 4 (OH) 6 • 8 H 2 O, was studied by means of rigorous theoretical solid-state calculations. The computations were carried out using Periodic Density Functional Theory with plane waves and pseudopotentials. The theoretical determination of this Raman spectrum was possible due to the previous development of a high-quality norm-conserving relativistic pseudopotential specific for the uranium atom and the recent optimization of the full crystal structure of this mineral, including the position of all hydrogen atoms in the corresponding unit cell. These two pieces of knowledge were formerly used in order to study the structural, mechanical, and thermodynamic properties of this mineral, but due to the very large size of the unit cell, the determination of the vibrational spectra was not possible. The corresponding results for the Raman spectrum, resulting from an intensive computational work, are reported here. The calculated Raman spectrum was compared with the experimental spectrum and the results were found to be in very good agreement. Therefore, a normal mode analysis of the theoretical spectra was performed to assign the main bands of the Raman spectrum. This assignment improved significantly the current empirical assignment of the bands of the Raman spectrum of becquerelite mineral.

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

Cited by 6 publications

References 129 publications

Theoretical Studies of the Structural, Mechanical and Raman Spectroscopic Properties of Uranyl-Containing Minerals

Theoretical Studies of the Structural, Mechanical and Raman Spectroscopic Properties of Uranyl-Containing Minerals

Thermodynamic, Raman Spectroscopic, and UV–Visible Optical Characterization of the Deltic, Squaric, and Croconic Cyclic Oxocarbon Acids

Periodic density functional theory study of the Raman spectrum of the hydrated uranyl oxyhydroxide mineral becquerelite

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