Research

14 pages, 398 KiB

Open AccessArticle

Principal Hugoniots of Promethium, Terbium, Thulium, Lutetium, and Actinium in a Wide Pressure Range

by Leonid Burakovsky, Dean L. Preston, Scott D. Ramsey, Sky K. Sjue, Charles E. Starrett and Roy S. Baty

Appl. Sci. 2023, 13(17), 9643; https://0-doi-org.brum.beds.ac.uk/10.3390/app13179643 - 25 Aug 2023

Cited by 2 | Viewed by 546

Abstract

We present the analytic forms of the principal Hugoniots of actinium (Ac) and the lanthanide promethium (Pm), which have both never been measured or calculated before, as well as those of terbium (Tb), thulium (Tm), and lutetium (Lu), the three least studied of [...] Read more.

We present the analytic forms of the principal Hugoniots of actinium (Ac) and the lanthanide promethium (Pm), which have both never been measured or calculated before, as well as those of terbium (Tb), thulium (Tm), and lutetium (Lu), the three least studied of the remaining lanthanides. They are based on our new analytic model of principal Hugoniot. A comparison of the five Hugoniots to our own independent theoretical calculations demonstrates very good agreement in every case, but each of the Hugoniots of Tb, Tm, and Ac from the TEFIS database, which ours are also compared to, appear to violate Johnson’s theoretical constraint

4 < η_{\max} < 7

for the maximum compression ratio

η_{\max}

, which corresponds to the Hugoniot turnaround point. Possible reason for this behavior of the TEFIS Hugoniots is briefly discussed. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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16 pages, 1188 KiB

Open AccessArticle

Magnetocaloric Properties and Critical Behaviour of the Sm₂Ni₁₇ Compound

by Jihed Horcheni, Kamal Nouri, Hamdi Jaballah, Lotfi Bessais, Essebti Dhahri and Mosbah Jemmali

Appl. Sci. 2023, 13(11), 6575; https://0-doi-org.brum.beds.ac.uk/10.3390/app13116575 - 29 May 2023

Cited by 1 | Viewed by 900

Abstract

This paper presents a detailed study in the critical region around the Curie temperature to determine the universality class of the Sm

_{2}

Ni

_{17}

intermetallic compound. The magnetocaloric effect has been studied on the basis of experimental measurements of magnetization. Maxwell’s relation [...] Read more.

This paper presents a detailed study in the critical region around the Curie temperature to determine the universality class of the Sm

_{2}

Ni

_{17}

intermetallic compound. The magnetocaloric effect has been studied on the basis of experimental measurements of magnetization. Maxwell’s relation and a phenomenological model are employed to find the change in magnetic entropy. The compound Sm

_{2}

Ni

_{17}

presents a variation in entropy with a moderate maximum and a wide range of operating temperatures. Numerous approaches have been used to explore the spontaneous magnetization behaviour and inverse of the susceptibility, including the modified Arrott technique, the Kouvel–Fisher approach, and the fitting of the critical isotherm. The scaling hypothesis has been used to confirm the validity and interdependence of the critical exponents associated with these phenomena. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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16 pages, 16661 KiB

Open AccessArticle

Ambient Melting Behavior of Stoichiometric Uranium-Plutonium Mixed Oxide Fuel

by Leonid Burakovsky, Scott D. Ramsey and Roy S. Baty

Appl. Sci. 2023, 13(10), 6303; https://0-doi-org.brum.beds.ac.uk/10.3390/app13106303 - 22 May 2023

Viewed by 830

Abstract

Mixed oxides of uranium and plutonium (MOX) are currently considered as a reference fuel for the new generation of fast breeder reactors such as ASTRID. The key factor determining the performance and safety of a fuel such as MOX is its operational limits [...] Read more.

Mixed oxides of uranium and plutonium (MOX) are currently considered as a reference fuel for the new generation of fast breeder reactors such as ASTRID. The key factor determining the performance and safety of a fuel such as MOX is its operational limits in the application environment which are closely related to the material’s structure and thermodynamic stability. They are in turn closely related to the ambient (zero pressure) melting point

(T_{m})

; thus,

T_{m}

is an important engineering parameter. Furthermore, PuO

_{2}

and UO

_{2}

are two endpoints of the phase diagram of MOX; therefore, their ambient

T_{m}

s are fundamental reference points. However, the current knowledge of the

T_{m}

of MOX is limited and controversial as several studies available in the literature do not converge on the unique behavior of

T_{m}

as a function of

x .

Specifically, some studies produced

T_{m}

as a monotonically decreasing function of x such that, with

T_{m}

of UO

_{2}

(x = 0)

of 3150 K,

T_{m}

of PuO

_{2}

(x = 1)

is ∼2650 K, while other studies resulted in

T_{m}

having a local minimum at

0.5 < x < 1

such that

T_{m}

of PuO

_{2}

is ∼3000 K, so that the difference between the two values of

T_{m}

is as high as 350 K. In this study, using the ab initio Z method implemented with the Vienna Ab Initio Simulation Package (VASP), we carry out a suite of quantum molecular dynamics simulations to obtain the ambient

T_{m}

of MOX at several values of

x,

0 < x < 1,

including the two end points

(x = 0,

x = 1) .

Our results agree with the behavior of

T_{m}

of MOX as a function of x having a local minimum at

x = 0.7

and

T_{m}

of PuO

_{2}

of 3050 K. Our study suggests potential ambient density–melting point systematics of MOX which may be useful in subsequent research on MOX such as its thermoelasticity modeling. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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9 pages, 732 KiB

Open AccessArticle

Exploring the Effect of the Number of Hydrogen Atoms on the Properties of Lanthanide Hydrides by DMFT

by Yao Wei, Elena Chachkarova, Evgeny Plekhanov, Nicola Bonini and Cedric Weber

Appl. Sci. 2022, 12(7), 3498; https://0-doi-org.brum.beds.ac.uk/10.3390/app12073498 - 30 Mar 2022

Viewed by 1486

Abstract

Lanthanide hydrogen-rich materials have long been considered as one of the candidates with high-temperature superconducting properties in condensed matter physics, and have been a popular topic of research. Attempts to investigate the effects of different compositions of lanthanide hydrogen-rich materials are ongoing, with [...] Read more.

Lanthanide hydrogen-rich materials have long been considered as one of the candidates with high-temperature superconducting properties in condensed matter physics, and have been a popular topic of research. Attempts to investigate the effects of different compositions of lanthanide hydrogen-rich materials are ongoing, with predictions and experimental studies in recent years showing that substances such as LaH

_{10}

, CeH

_{9}

, and LaH

_{16}

exhibit extremely high superconducting temperatures between 150–250 GPa. In particular, researchers have noted that, in those materials, a rise in the f orbit character at the Fermi level combined with the presence of hydrogen vibration modes at the same low energy scale will lead to an increase in the superconducting transition temperature. Here, we further elaborate on the effect of the ratios of lanthanide to hydrogen in these substances with the aim of bringing more clarity to the study of superhydrides in these extreme cases by comparing a variety of lanthanide hydrogen-rich materials with different ratios using the dynamical mean-field theory (DMFT) method, and provide ideas for later structural predictions and material property studies. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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19 pages, 3959 KiB

Open AccessArticle

Thermodynamics Modeling for Actinide Monocarbides and Mononitrides from First Principles

by Per Söderlind, Emily E. Moore and Christine J. Wu

Appl. Sci. 2022, 12(2), 728; https://0-doi-org.brum.beds.ac.uk/10.3390/app12020728 - 12 Jan 2022

Cited by 5 | Viewed by 1380

Abstract

The high-temperature thermodynamical properties for the actinide monocarbides and mononitrides ThC, ThN, UC, UN, PuC, and PuN are calculated from first-principles electronic-structure theory. The electronic structure is modeled with density-functional theory (DFT) and is fully relativistic, including the spin-orbit interaction. Furthermore, the DFT [...] Read more.

The high-temperature thermodynamical properties for the actinide monocarbides and mononitrides ThC, ThN, UC, UN, PuC, and PuN are calculated from first-principles electronic-structure theory. The electronic structure is modeled with density-functional theory (DFT) and is fully relativistic, including the spin-orbit interaction. Furthermore, the DFT is extended to account for orbital–orbital interactions, by means of a parameter-free orbital-polarization (OP) technique, that has proven to be essential for the 5f electrons in plutonium. Strong anharmonicity and the temperature dependence of the lattice vibrations are captured with the self-consistent ab initio lattice dynamics (SCAILD) method. The calculated free energies and heat capacities are compared to published results from quasi-harmonic (QH) theory, and experiments, where available. For the uranium and plutonium compounds, we make use of CALPHAD assessments to help evaluate the theory. Generally, our anharmonic relativistic approach compares well with both CALPHAD and experiments. For the thorium compounds, our theory is in good accord with QH modeling of the free energy at lower temperatures but for the heat capacity the comparison is less favorable. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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19 pages, 4507 KiB

Open AccessArticle

The Limitations of 5f Delocalization and Dispersion

by J. G. Tobin, S. Nowak, S. W. Yu, R. Alonso-Mori, T. Kroll, D. Nordlund, T. C. Weng and D. Sokaras

Appl. Sci. 2021, 11(9), 3882; https://0-doi-org.brum.beds.ac.uk/10.3390/app11093882 - 25 Apr 2021

Cited by 6 | Viewed by 1994

Abstract

Delocalization in the 5f states of the actinides is an important phenomenon, but poorly quantified. Here, the fundamental limitations of 5f dispersion measurements using angle and momentum resolved variants of photoelectron spectroscopy will be discussed. A novel approach will be suggested, based on [...] Read more.

Delocalization in the 5f states of the actinides is an important phenomenon, but poorly quantified. Here, the fundamental limitations of 5f dispersion measurements using angle and momentum resolved variants of photoelectron spectroscopy will be discussed. A novel approach will be suggested, based on a theoretical projection, which should circumvent these limitations: M_4,5 X-ray emission spectroscopy. This analysis will utilize the case study of U metal, which can be considered to be the paramount example of 5f dispersion. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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16 pages, 312 KiB

Open AccessArticle

Calibration of Melt, Shear Modulus, and Flow Stress Models for Cerium Subjected to Intensive Dynamic Loading

by Marvin A. Zocher, JeeYeon N. Plohr and Leonid Burakovsky

Appl. Sci. 2020, 10(20), 7209; https://0-doi-org.brum.beds.ac.uk/10.3390/app10207209 - 16 Oct 2020

Viewed by 1267

Abstract

Calibration parameters are developed for melt, shear modulus, and flow stress models for cerium subjected to dynamic loading. Parametric calibration is developed for the Lindemann melt law and for the shear modulus and flow stress models of Steinberg, Cochran, and Guinan. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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16 pages, 2742 KiB

Open AccessArticle

Thermodynamics of Plutonium Monocarbide from Anharmonic and Relativistic Theory

by Per Söderlind, Alexander Landa, Aurélien Perron, Emily E. Moore and Christine Wu

Appl. Sci. 2020, 10(18), 6524; https://0-doi-org.brum.beds.ac.uk/10.3390/app10186524 - 18 Sep 2020

Cited by 4 | Viewed by 1829

Abstract

Thermodynamics of plutonium monocarbide is studied from first-principles theory that includes relativistic electronic structure and anharmonic lattice vibrations. Density-functional theory (DFT) is expanded to include orbital-orbital coupling in addition to the relativistic spin-orbit interaction for the electronic structure and it is combined with [...] Read more.

Thermodynamics of plutonium monocarbide is studied from first-principles theory that includes relativistic electronic structure and anharmonic lattice vibrations. Density-functional theory (DFT) is expanded to include orbital-orbital coupling in addition to the relativistic spin-orbit interaction for the electronic structure and it is combined with anharmonic, temperature dependent, lattice dynamics derived from the self-consistent ab initio lattice dynamics (SCAILD) method. The obtained thermodynamics are compared to results from simpler quasi-harmonic theory and experimental data. Formation enthalpy, specific heat, and Gibbs energy calculated from the anharmonic model are validated by direct comparison with a calculation of phase diagram (CALPHAD) assessment of PuC and sub-stochiometric PuC_0.896. Overall, the theory reproduces CALPHAD results and measured data for PuC rather well, but the comparison is hampered by the sub-stoichiometric nature of plutonium monocarbide. It was found that a bare theoretical approach that ignores spin-orbit and orbital-orbital coupling (orbital polarization) of the plutonium 5f electrons promotes too soft phonons and Gibbs energies that are incompatible with that of the CALPHAD assessment of the experimental data. The investigation of PuC suggests that the electronic structure is accurately described by plutonium 5f electrons as “band like” and delocalized, but correlate through spin polarization, orbital polarization, and spin-orbit coupling, in analogy to previous findings for plutonium metal. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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21 pages, 2130 KiB

Open AccessFeature PaperArticle

Thermodynamics and Magnetism of YCo₅ Compound Doped with Fe and Ni: An Ab Initio Study

by Alexander Landa, Per Söderlind, Emily E. Moore and Aurelien Perron

Appl. Sci. 2020, 10(17), 6037; https://0-doi-org.brum.beds.ac.uk/10.3390/app10176037 - 31 Aug 2020

Cited by 6 | Viewed by 2927

Abstract

YCo₅ permanent magnet exhibits high uniaxial magnetocrystalline anisotropy energy and has a high Curie temperature. These are good properties for a permanent magnet, but YCo₅ has a low energy product, which is notably insufficient for a permanent magnet. In order to [...] Read more.

YCo₅ permanent magnet exhibits high uniaxial magnetocrystalline anisotropy energy and has a high Curie temperature. These are good properties for a permanent magnet, but YCo₅ has a low energy product, which is notably insufficient for a permanent magnet. In order to improve the energy product in YCo₅, we suggest replacing cobalt with iron, which has a much bigger magnetic moment. With a combination of density-functional-theory calculations and thermodynamic CALculation of PHAse Diagrams (CALPHAD) modeling, we show that a new magnet, YFe₃(Ni_1-xCo_x)₂, is thermodynamically stable and exhibits an improved energy product without significant detrimental effects on the magnetocrystalline anisotropy energy or the Curie temperature. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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9 pages, 691 KiB

Open AccessArticle

Thermodynamics of Uranium Tri-Iodide from Density-Functional Theory

by Per Söderlind, Aurélien Perron, Emily E. Moore, Alexander Landa and Tae Wook Heo

Appl. Sci. 2020, 10(11), 3914; https://0-doi-org.brum.beds.ac.uk/10.3390/app10113914 - 05 Jun 2020

Cited by 2 | Viewed by 2454

Abstract

Density-functional theory (DFT) is employed to investigate the thermodynamic and ground-state properties of bulk uranium tri-iodide, UI₃. The theory is fully relativistic and electron correlations, beyond the DFT and generalized gradient approximation, are addressed with orbital polarization. The electronic structure indicates [...] Read more.

Density-functional theory (DFT) is employed to investigate the thermodynamic and ground-state properties of bulk uranium tri-iodide, UI₃. The theory is fully relativistic and electron correlations, beyond the DFT and generalized gradient approximation, are addressed with orbital polarization. The electronic structure indicates anti-ferromagnetism, in agreement with neutron diffraction, with band gaps and a non-metallic system. Furthermore, the formation energy, atomic volume, crystal structure, and heat capacity are calculated in reasonable agreement with experiments, whereas for the elastic constants experimental data are unavailable for comparison. The thermodynamical properties are modeled within a quasi-harmonic approximation and the heat capacity and Gibbs free energy as functions of temperature agree with available calculation of phase diagram (CALPHAD) thermodynamic assessment of the experimental data. Full article

(This article belongs to the Special Issue Experimental and Theoretical Studies on the Physical Properties of Lanthanides, Actinides, and Their Compounds)

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