Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
4.5
2.7
Journals
Applied Sciences
Special Issues
Experimental and Theoretical Studies on the Physical Properties of Actinides...
share announcement

Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: closed (31 May 2020) | Viewed by 31575

Special Issue Editor

Dr. Leonid Burakovsky

E-Mail Website
Guest Editor
Theoretical Division, T-1, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Interests: phase diagram of condensed matter, equation of state, phase transitions; topological properties of condensed matter, linear defects: dislocations, disclinations, defect-mediated phase transitions, geometrical frustration; amorphous, granular, and polycrystalline matter; shock waves in granular and polycrystalline materials; analytic modeling of the physical properties of condensed matter; molecular dynamics (MD) simulations, both classical (MolDy, DL−POLY) and first-principles quantum (VASP); phase diagram studies; high pressure – high temperature polymorphism
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The fundamental understanding of the physical properties of actinides is of considerable practical importance for space research, industrial radiography, geological prospecting, and medical applications. The fundamental understanding of the physical properties of their oxides, specifically under intense radiation and high temperature gradients, is crucial for predicting the performance of nuclear reactor fuels. The actinide elements are now sufficiently well understood to establish analogies of their physical properties and those of rare-earth and transition elements for which certain systematics exist. Past research on actinides has revealed systematic variations in bonding properties such as bulk modulus and melting point, transport properties such as resistivity, and electronic properties such as specific heat. The lighter actinides are believed to exhibit a transition type behavior, however a substantial contribution to bonding is made by 5f electrons. There are also important differences between the behavior of the heavier actinides and those of rare earth elements. The potential economic gains from the fundamental understanding of the physical properties of actinides are their oxides, which are more effective for everyday use, and which are very likely to ensure continuing research activity that will keep advancing this field of research.

This Special Issue is aimed at highlighting the current state-of-the-art of both experimental and theoretical research on the physical properties of actinides and their oxides, on a broad spectrum of topics such as equations of state, phase diagrams, mechanical and thermophysical properties, elasticity, plasticity, strength, and damage. Theoretical studies will include both modeling and computer simulations. Original contributions from researchers in all the fields relevant to the physical properties of actinides and their oxides are welcome. All manuscripts will undergo peer review process prior to publication.

Dr. Leonid Burakovsky
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (10 papers)

Download All Papers
Order results
Result details
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:

Research

Jump to: Review, Other

15 pages, 3203 KiB  
Article
Ab Initio Study of the Effect of Mono-Vacancies on the Metastability of Ga-Stabilized δ-Pu
by Sarah C. Hernandez and Franz J. Freibert
Appl. Sci. 2020, 10(21), 7628; https://doi.org/10.3390/app10217628 - 29 Oct 2020
Cited by 4 | Viewed by 2091
Abstract
Most experimental studies on metallic Pu are on the room temperature monoclinic α-phase or the fcc Ga stabilized δ-phase. Stabilized δ-phase Pu-Ga alloys are metastable and exhibit a martensitic phase transformation to α’-phase at low temperatures, or applied shear, with concentrations lower than [...] Read more.
Most experimental studies on metallic Pu are on the room temperature monoclinic α-phase or the fcc Ga stabilized δ-phase. Stabilized δ-phase Pu-Ga alloys are metastable and exhibit a martensitic phase transformation to α’-phase at low temperatures, or applied shear, with concentrations lower than three atomic percent Ga. By using first principles, we explore the metastability of δ-phase by investigating the structural and electronic behavior induced by Ga alloying and by a mono-vacancy point defect. We find that a site substitutional Ga induces a tetragonal distortion in the lattice affected by hybridization of Ga 4p and Pu 6d states. With the addition of a mono-vacancy, a monoclinic or tetragonal distortion forms locally (dependent on its distance from Ga), and decoupling of the Pu 5f and 6d states and broadening of the 6d states occurs. This response enables hybridization of Pu 6d with the Ga 4p states affecting the mono-vacancy formation energy. Thus, stabilization of the fcc lattice correlates with hybridization of Pu 6d states with Ga 4p states, and this becomes more evident in the presence of a mono-vacancy. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

17 pages, 3110 KiB  
Article
Phase Stability in U-6Nb Alloy Doped with Ti from the First Principles Theory
by Alexander Landa, Per Söderlind and Amanda Wu
Appl. Sci. 2020, 10(10), 3417; https://doi.org/10.3390/app10103417 - 15 May 2020
Cited by 9 | Viewed by 2933
Abstract
First-principles calculations within the density-functional-theory (DFT) approach are conducted in order to explore and explain the effect of small amounts of titanium on phase stability in the U-6Nb alloy. During rapid quenching from high to room temperature, metastable phases α′ (orthorhombic), α″ (monoclinic), [...] Read more.
First-principles calculations within the density-functional-theory (DFT) approach are conducted in order to explore and explain the effect of small amounts of titanium on phase stability in the U-6Nb alloy. During rapid quenching from high to room temperature, metastable phases α′ (orthorhombic), α″ (monoclinic), and γ0 (tetragonal) can form, depending on Nb concentration. Important mechanical properties depend on the crystal structure and, therefore, an understanding of the effect of impurities on phase stability is essential. Insights on this issue are obtained from quantum-mechanical DFT calculations. The DFT framework does not rely on any material-specific assumptions and is therefore ideal for an unbiased investigation of the U-Nb system. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

14 pages, 2490 KiB  
Article
Towards the Quantification of 5f Delocalization
by J. G. Tobin, S. Nowak, S.-W. Yu, R. Alonso-Mori, T. Kroll, D. Nordlund, T.-C. Weng and D. Sokaras
Appl. Sci. 2020, 10(8), 2918; https://doi.org/10.3390/app10082918 - 23 Apr 2020
Cited by 12 | Viewed by 2151
Abstract
By using M4,5 X-ray Emission Spectroscopy (XES) in the tender X-ray regime, it is possible to quantify 5f delocalization in the actinides. Previous analyses, utilizing the Branching Ratio (BR) in the N4,5 X-ray Absorption Spectroscopy (XAS), could not discriminate between the [...] Read more.
By using M4,5 X-ray Emission Spectroscopy (XES) in the tender X-ray regime, it is possible to quantify 5f delocalization in the actinides. Previous analyses, utilizing the Branching Ratio (BR) in the N4,5 X-ray Absorption Spectroscopy (XAS), could not discriminate between the cases of localized n = 2 and delocalized n = 3, in uranium materials, where n is the number of 5f electrons on the U entity. Here, it is shown that, by employing the ubiquitous 6p → 3d XES as a point of normalization, the localized n = 2 and delocalized n = 3 cases can be easily distinguished and quantified. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

13 pages, 4230 KiB  
Article
Phonon Scattering and Thermal Conductivity of Actinide Oxides with Defects
by Katherine Mitchell, Jungkyu Park, Alex Resnick, Hunter Horner and Eduardo B. Farfan
Appl. Sci. 2020, 10(5), 1860; https://doi.org/10.3390/app10051860 - 09 Mar 2020
Cited by 6 | Viewed by 2713
Abstract
In the present study, we examine the effect of point defects and fission gases on thermal transport in representative actinide oxides used in modern reactors. In particular, oxygen interstitials and Kr/Xe fission gas bubbles are of primary focus. Reverse non-equilibrium molecular dynamics is [...] Read more.
In the present study, we examine the effect of point defects and fission gases on thermal transport in representative actinide oxides used in modern reactors. In particular, oxygen interstitials and Kr/Xe fission gas bubbles are of primary focus. Reverse non-equilibrium molecular dynamics is employed to investigate thermal transport in UO2 and PuO2 with oxygen interstitials at the defect concentrations of 0.1%, 1%, and 5%. The results show that any alteration to the lattice structures of these fuels reduce their thermal conductivities significantly. For the largest UO2 structure simulated in the present study, for example, 0.1% oxygen interstitials decreased the thermal conductivity by 18.6%. For the case of the effect of fission gas bubbles, serious modification to phonon dispersion in oxide fuels is caused by the presence of a single fission gas bubble, resulting in a large temperature drop in their temperature profiles. The average interfacial thermal resistance across a fission gas bubble (comprised of 30 Kr and/or Xe atoms) is estimated to be 2.1 × 10−9 Km2/W. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

24 pages, 3502 KiB  
Article
The Conundrum of Relaxation Volumes in First-Principles Calculations of Charged Defects in UO2
by Anuj Goyal, Kiran Mathew, Richard G. Hennig, Aleksandr Chernatynskiy, Christopher R. Stanek, Samuel T. Murphy, David A. Andersson, Simon R. Phillpot and Blas P. Uberuaga
Appl. Sci. 2019, 9(24), 5276; https://doi.org/10.3390/app9245276 - 04 Dec 2019
Cited by 11 | Viewed by 4009
Abstract
The defect relaxation volumes obtained from density-functional theory (DFT) calculations of charged vacancies and interstitials are much larger than their neutral counterparts, seemingly unphysically large. We focus on UO2 as our primary material of interest, but also consider Si and GaAs to [...] Read more.
The defect relaxation volumes obtained from density-functional theory (DFT) calculations of charged vacancies and interstitials are much larger than their neutral counterparts, seemingly unphysically large. We focus on UO2 as our primary material of interest, but also consider Si and GaAs to reveal the generality of our results. In this work, we investigate the possible reasons for this and revisit the methods that address the calculation of charged defects in periodic DFT. We probe the dependence of the proposed energy corrections to charged defect formation energies on relaxation volumes and find that corrections such as potential alignment remain ambiguous with regards to its contribution to the charged defect relaxation volume. We also investigate the volume for the net neutral defect reactions comprising individual charged defects, and find that the aggregate formation volumes have reasonable magnitudes. This work highlights the issue that, as is well-known for defect formation energies, the defect formation volumes depend on the choice of reservoir. We show that considering the change in volume of the electron reservoir in the formation reaction of the charged defects, analogous to how volumes of atoms are accounted for in defect formation volumes, can renormalize the formation volumes of charged defects such that they are comparable to neutral defects. This approach enables the description of the elastic properties of isolated charged defects within an overall neutral material. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

25 pages, 5798 KiB  
Article
Development of a CALPHAD Thermodynamic Database for Pu-U-Fe-Ga Alloys
by Emily E. Moore, Patrice E.A. Turchi, Alexander Landa, Per Söderlind, Benoit Oudot, Jonathan L. Belof, Stephen A. Stout and Aurélien Perron
Appl. Sci. 2019, 9(23), 5040; https://doi.org/10.3390/app9235040 - 22 Nov 2019
Cited by 18 | Viewed by 6502
Abstract
The interaction of actinides and actinide alloys such as the δ-stabilized Pu-Ga alloy with iron is of interest to understand the impurity effects on phase stability. A newly developed and self-consistent CALPHAD thermodynamic database is presented which covers the elements: Pu, U, Fe, [...] Read more.
The interaction of actinides and actinide alloys such as the δ-stabilized Pu-Ga alloy with iron is of interest to understand the impurity effects on phase stability. A newly developed and self-consistent CALPHAD thermodynamic database is presented which covers the elements: Pu, U, Fe, Ga across their whole composition and temperature ranges. The phase diagram and thermodynamic properties of plutonium-iron (Pu-Fe) and uranium-iron (U-Fe) systems are successfully reassessed, with emphasis on the actinide rich side. Density functional theory (DFT) calculations are performed to validate the stability of the stoichiometric (Pu,U)6Fe and (Pu,U)Fe2 compounds by computing their formation enthalpies. These data are combined to construct the Pu-U-Fe ternary phase diagram. The thermodynamic assessment of Fe-Ga is presented for the first time and application to the quaternary Pu-U-Fe-Ga system is discussed. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

14 pages, 1502 KiB  
Article
Assessing Relativistic Effects and Electron Correlation in the Actinide Metals Th to Pu
by Babak Sadigh, Andrey Kutepov, Alexander Landa and Per Söderlind
Appl. Sci. 2019, 9(23), 5020; https://doi.org/10.3390/app9235020 - 21 Nov 2019
Cited by 21 | Viewed by 3003
Abstract
Density functional theory (DFT) calculations are employed to explore and assess the effects of the relativistic spin–orbit interaction and electron correlations in the actinide elements. Specifically, we address electron correlations in terms of an intra-atomic Coulomb interaction with a Hubbard U parameter (DFT [...] Read more.
Density functional theory (DFT) calculations are employed to explore and assess the effects of the relativistic spin–orbit interaction and electron correlations in the actinide elements. Specifically, we address electron correlations in terms of an intra-atomic Coulomb interaction with a Hubbard U parameter (DFT + U). Contrary to recent beliefs, we show that for the ground-state properties of the light actinide elements Th to Pu, the DFT + U makes its best predictions for U = 0. Actually, our modeling suggests that the most popular DFT + U formulation leads to the wrong ground-state phase for plutonium. Instead, extending DFT and the generalized gradient approximation (GGA) with orbital–orbital interaction (orbital polarization; OP) is the most accurate approach. We believe the confusion in the literature on the subject mostly originates from incorrectly accounting for the spin–orbit (SO) interaction for the p1/2 state, which is not treated in any of the widely used pseudopotential plane-wave codes. Here, we show that for the actinides it suffices to simply discard the SO coupling for the p states for excellent accuracy. We thus describe a formalism within the projector-augmented-wave (PAW) scheme that allows for spin–orbit coupling, orbital polarization, and non-collinear magnetism, while retaining an efficient calculation of Hellmann–Feynman forces. We present results of the ground-state phases of all the light actinide metals (Th to Pu). Furthermore, we conclude that the contribution from OP is generally small, but substantial in plutonium. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

11 pages, 1461 KiB  
Article
Ground-State and Thermodynamical Properties of Uranium Mononitride from Anharmonic First-Principles Theory
by Per Söderlind, Alexander Landa, Aurélien Perron, Babak Sadigh and Tae Wook Heo
Appl. Sci. 2019, 9(18), 3914; https://doi.org/10.3390/app9183914 - 18 Sep 2019
Cited by 14 | Viewed by 3652
Abstract
We report on an advanced density-functional theory (DFT) approach for investigating the ground-state and thermodynamical properties of uranium mononitride (UN). The electronic structure for UN at zero temperature is obtained from DFT that utilizes the generalized gradient approximation (GGA) for the electron exchange [...] Read more.
We report on an advanced density-functional theory (DFT) approach for investigating the ground-state and thermodynamical properties of uranium mononitride (UN). The electronic structure for UN at zero temperature is obtained from DFT that utilizes the generalized gradient approximation (GGA) for the electron exchange and correlation functional and includes spin-orbit interaction and an extension with orbital polarization. Thermodynamical properties are computed within the quasi-harmonic approximation in the Debye–Grüneisen model while anharmonicity is captured in the self-consistent ab initio lattice dynamics (SCAILD) scheme. Anharmonic phonons have heretofore never been modeled from first-principles for UN but they turn out to be important. The computed free energy compares well with that of a CALPHAD (CALculation of PHAse Diagrams) assessment of available experimental data. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Figure 1

Review

Jump to: Research, Other

17 pages, 3703 KiB  
Review
Water on Actinide Dioxide Surfaces: A Review of Recent Progress
by Gaoxue Wang, Enrique R. Batista and Ping Yang
Appl. Sci. 2020, 10(13), 4655; https://doi.org/10.3390/app10134655 - 06 Jul 2020
Cited by 13 | Viewed by 2709
Abstract
The fluorite structured actinide dioxides (AnO2), especially UO2, are the most common nuclear fuel materials. A comprehensive understanding of their surface chemistry is critical because of its relevance to the safe handling, usage, and storage of nuclear fuels. Because [...] Read more.
The fluorite structured actinide dioxides (AnO2), especially UO2, are the most common nuclear fuel materials. A comprehensive understanding of their surface chemistry is critical because of its relevance to the safe handling, usage, and storage of nuclear fuels. Because of the ubiquitous nature of water (H2O), its interaction with AnO2 has attracted significant attention for its significance in studies of nuclear fuels corrosion and the long-term storage of nuclear wastes. The last few years have seen extensive experimental and theoretical studies on the H2O–AnO2 interaction. Herein, we present a brief review of recent advances in this area. We focus on the atomic structures of AnO2 surfaces, the surface energies, surface oxygen vacancies, their influence on the oxidation states of actinide atoms, and the adsorption and reactions of H2O on stoichiometric and reduced AnO2 surfaces. Finally, a summary and outlook of future studies on surface chemistry of AnO2 are given. We intend for this review to encourage broader interests and further studies on AnO2 surfaces. Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
►▼ Show Figures

Graphical abstract

Other

Jump to: Research, Review

1 pages, 137 KiB  
Erratum
Erratum: Towards the Quantification of 5f Delocalization. Applied Sciences 2020, 10, 2918
by Applied Sciences Editorial Office
Appl. Sci. 2020, 10(12), 4242; https://doi.org/10.3390/app10124242 - 20 Jun 2020
Cited by 5 | Viewed by 1222
Abstract
We wish to make the following correction to the published paper [...] Full article
(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Actinides and Their Oxides)
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-10
Back to TopTop