Special Issue "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".

Deadline for manuscript submissions: 31 January 2020.

Special Issue Editor

Dr. Leonid Burakovsky
E-Mail Website
Guest Editor
Theoretical Division, T-1, MS B221, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Tel. (505) 667-5222
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 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 papers will be 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 1800 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 (4 papers)

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Research

Open AccessArticle
The Conundrum of Relaxation Volumes in First-Principles Calculations of Charged Defects in UO2
Appl. Sci. 2019, 9(24), 5276; https://doi.org/10.3390/app9245276 - 04 Dec 2019
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
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Open AccessArticle
Development of a CALPHAD Thermodynamic Database for Pu-U-Fe-Ga Alloys
Appl. Sci. 2019, 9(23), 5040; https://doi.org/10.3390/app9235040 - 22 Nov 2019
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
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Open AccessFeature PaperArticle
Assessing Relativistic Effects and Electron Correlation in the Actinide Metals Th to Pu
Appl. Sci. 2019, 9(23), 5020; https://doi.org/10.3390/app9235020 - 21 Nov 2019
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
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Open AccessFeature PaperArticle
Ground-State and Thermodynamical Properties of Uranium Mononitride from Anharmonic First-Principles Theory
Appl. Sci. 2019, 9(18), 3914; https://doi.org/10.3390/app9183914 - 18 Sep 2019
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
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Group of Dr. Landa from Lawrence Livermore National Laboratory will contribute 2 papers in theoretical studies, on actinides specifically.

2. Group of Dr. Yang from Los Alamos National Laboratory will contribute 1 paper;

3. The Guest Editor Dr. Leonid Burakovsky will write a paper for this Special Issue.

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