Uranium Atoms Research Articles

Molecular dynamics simulations of uranyl and plutonyl cations in a task-specific ionic liquid.

Ionic liquids (ILs) are a unique class of solvents with potential applications in advanced separation technologies relevant to the nuclear industry. ILs are salts with low melting points and a wide range of tunable physical properties, such as viscosity, hydrophobiciy, conductivity, and liquidus range. ILs have negligible vapor pressure, are often non-flammable, and can have high thermal stability and a wide electrochemical window, making them attractive for use in separations processes relevant to the nuclear industry. Metal salts generally have a low solubility in ILs; however, by incorporating new functional groups into the IL cation or anion that promote complexation with the metal, the solubility can be greatly increased. One such task-specific ionic liquid (TSIL) is 1-carboxy-N, N, N-trimethylglycine bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]) [Nockemann et al., J. Phys. Chem. B 110, 20978-20992 (2006)]. Water, which is detrimental for electrochemical separations, is a common impurity in ILs and can coordinate with actinyl cations, particularly in ILs containing only weakly coordinating components. Understanding the behavior of actinides in TSIL/water mixtures on a molecular level is vital for designing improved separations processes. Classical molecular dynamics simulations of uranyl(VI) and plutonyl(VI) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]) with deprotonated Hbet (betaine) and water have been performed to understand the coordination and dynamics of the actinyl cations. We find that betaine is a much stronger ligand than water and prefers to coordinate the metal in a bidentate manner. Potential of mean force simulations yield a relative free energy for betaine coordination of approximately -120 to -90 kJ/mol in mixtures with water. As the amount of betaine coordinated to the actinide increases, the diffusion coefficient of the actinyl cation decreases. Moreover, the betaine ligand is able to bridge between two metal centers, resulting in dimeric complexes with actinide-actinide distances of ∼5Å. Potential of mean force simulations show that these structures are stable, with relative free energies of up to -40 kJ/mol. The crystal structure for [(UO2)2(bet)6(H2O)2][Tf2N]4 shows that the betaine bridges between two uranium atoms to form dimeric complexes similar to those found in our simulations [Nockemann et al. Inorg. Chem. 49, 3351-33601 (2010)].

Theoretical Investigation on One-Electron ϕ···ϕ Bonding in Diuranium Inverse Sandwich U2B6 Complex Enabled by a B6 Ring.

Traditional σ, π, and δ types of covalent chemical bonding have been extensively studied for nearly a century. In contrast, ϕ-type bonding involving nf (n = 4, 5) orbitals has received less attention due to their high contraction and minimal orbital overlap. Herein, we theoretically predict a singly occupied ϕ···ϕ bonding between two 5f orbitals, facilitated by B6 group orbitals in the hexa-boron diuranium inverse sandwich structure of U2B6. From ab initio quantum chemical calculations, the global minimum structure has a septuplet state with D6h symmetry. Chemical bonding analyses reveal that the 5f and 6d atomic orbitals of the two uranium atoms interact with the ligand orbitals of the central B6 ring, exhibiting favorable energy matching and symmetry compatibility to form delocalized σ-, π-, δ-, and ϕ-type bonding orbitals. Notably, even though the ϕ···ϕ bonding orbital is singly occupied, it still has a significant role in stability and cannot be overlooked. Furthermore, the U2B6 cluster model can be viewed as a building block of UB2 solid materials from both geometric and electronic perspectives. This work predicts the first example of ϕ···ϕ bonding, highlighting the complexity and diversity of chemical bonds formed in actinide boride clusters.

A characterization method for reprocessed spent nuclear fuel through neutron and gamma-ray multiplicity counting

It is difficult to measure neutrons and gamma rays coming directly from uranium and plutonium atoms in pyroprocessed ingot, which is of great interest to nuclear safeguards. Most neutrons of the ingot are emitted from 244Cm isotope and gamma rays from its fission products. Therefore, it is necessary to identify spent fuel characteristics such as initial enrichment, burnup and cooling time from measurement and estimate plutonium mass from calibration curve or burnup calculations.In this study, we explored the possibility of characterizing pyroprocessed ingots using neutron and gamma-ray multiplicity counting. We particularly focused on finding the possible correlation between neutron and gamma-ray multiplicity properties (singles, doubles, and triples) and spent fuel properties for U/TRU/RE preprocessed ingot. We examined neutron and gamma-ray correlation for spent fuel, using the Cascading Gamma-ray Multiplicity with Fission (CGMF) and the Fission Reaction Event Yield Algorithm (FREYA) library in MCNP6.2. Due to high spontaneous fission rate, neutron and gamma-ray multiplicity parameters did not strongly correlate with multiplication factor from the point model but was proportional to 244Cm mass. The results based on the CGMF and FREYA fission library showed the similar trends for neutron and gamma-ray cases. The sum of two multiplicity data yielded best linearity with the 244Cm effective mass. Although total neutron counting (S) alone was sufficient for effectively characterizing spent fuel due to its strong linearity, this feasibility study confirmed that, in principle, it will be more effective to calculate the sum of neutron and gamma-ray multiplicity properties to directly estimate the mass of 244Cm, rather than relying on the conventional method of calculating the multiplication factor.

Molecular Models of Atomically Dispersed Uranium at MoS2 Surfaces Reveal Cooperative Mechanism of Water Reduction.

Single atoms of uranium supported on molybdenum sulfide surfaces (U@MoS2) have been recently demonstrated to facilitate the hydrogen evolution reaction (HER) through electrocatalysis. Theoretical calculations have predicted uranium hydroxide moieties bound to edge-sulfur atoms of MoS2 as a proposed transition state involved in the HER process. However, the isolation of relevant intermediates involved in this process remains a challenge, rendering mechanistic hypotheses unverified. The present work describes the isolation and characterization of a uranium-hydroxide intermediate on molybdenum sulfide surfaces using [(Cp*3Mo3S4)UCp*], a molecular model of a reduced uranium center supported at MoS2. Mechanistic investigations highlight the metalloligand cooperativity with uranium involved in the water activation pathway. The corresponding uranium-oxo analogue, [(Cp*3Mo3S4)Cp*U(═O)], was also accessed from the hydroxide cluster via hydrogen atom transfer and from [(Cp*3Mo3S4)UCp*] through an alternative direct oxygen atom transfer. These results provide an atomistic perspective on the reactivity of low-valent uranium at molybdenum sulfide surfaces toward water, modeling key intermediates associated with the HER of U@MoS2 catalysts.

Effect of fission products on the thermal conductivity of ThO2-A molecular dynamics study

Thermal conductivity (k), as an important thermal property of nuclear fuels, would be deteriorated due to fission products. Therefore, to investigate the effect of fission products on the thermal conductivity of nuclear fuels is essential. Two typical fission products: Xe and Kr with 0–2 % concentration are considered in this work. The lattice constants (L) of ThO2 increase due to fission products at all testing temperatures. The extent of increase in L due to Xe interstitials is the maximum. The fission products significantly reduce the thermal conductivity of ThO2. The extent of reduction in thermal conductivity of ThO2 by the defects follows the trend Xe (interstitials) > Xe (substitutional defects) > Kr (substitutional defects) > Kr (interstitials). Finally, the full-filled Xe/Kr bubble has a nearly identical thermal conductivity as an empty void or half-filled Xe/Kr bubble. The underlying reason may be that the thorium atoms have a lower mobility than uranium atoms. These calculated values can be used to predict the thermal properties of the irradiated ThO2.

Properties and mechanism of uranium adsorption on single-sided fluorinated graphene: A first-principles study

Functionalized two-dimensional materials have been widely explored as possible candidates to adsorb radioactive nuclide due to their large specific surface and tunable properties. In this work, single-sided fluorinated graphene (ssFG) with different fluorinated rates have been predicted to be an effective adsorbent for uranium atoms using density functional theory (DFT) simulations. The linear response method was used to obtain a more accurate Hubbard U value (3.1 eV) of the 5f orbital of the uranium atom. Our calculated results show that uranium atoms were energetically favorable adsorbed on the C2F, C6F, C8F ssFGs, and their adsorption energies are 3.45, 1.20, and 1.12 eV, respectively. The electronic analysis, such as the density of states, charge transfer and differential charge density suggest that the uranium atom has the strongest chemisorption with the substrate C2F. C2F also exhibits excellent performance in terms of the adsorption capacity of uranium atoms. In addition, the critical temperature for the adsorption-desorption transition of uranium atoms was predicted to be 632 K by the adsorption rate equation. The results suggest that ssFG, especially C2F, was a promising material for uranium adsorption, have promising application in nuclear waste disposal, extraction of uranium from seawater, uranium detection, etc.

New Polymorphic Structures of Uranyl Butyrate and Crotonate

AbstractNew polymorphs of diaquadicrotonato‐ and diaquadibutyratodioxidouranium(VI) were synthesized. X‐ray diffraction analysis at low and room temperatures revealed the monoclinic crystal system for both compounds at both room and low temperatures. New structures contain molecular complexes in which uranium atoms are coordinated by two bidentate carboxylate ions and two water molecules. The crystal structures feature the same packing motif that constitutes layers formed by hydrogen bonds. IR spectroscopy uncovered differences in vibrations of carboxyl and uranyl groups. Voronoi‐Dirichlet parameters of the synthesized compounds and some previously published uranyl carboxylates that have similar complex and crystal structures to the new ones were compared. The new structures demonstrate once again that the volume of Voronoi‐Dirichlet polyhedron of the uranium atom in U sublattice depends on the nature of carboxylate ion alkyl chain.

Frustration—no frustration crossover and phase transitions in 2D spin models with zig-zag structures

Three 2D spin models made of frustrated zig-zag chains with competing interactions which, by exact summation with respect to some degrees of freedom, can be replaced by an effective temperature-dependent interaction, were considered. The first model, exactly solvable Ising chains coupled by only four-spin interactions, does not exhibit any finite temperature phase transition; nevertheless, temperature can trigger a frustration–no frustration crossover accompanied by gigantic specific heat. A similar effect was observed in several two-leg ladder models (Weiguo 2020 arXiv:2006.08921v2; 2020 2006.15087v1). The anisotropic Ising chains coupled by a direct interchain interaction and, competing with it, indirect interaction via spins located between chains, are analyzed using the exact Onsager’s equation and linear perturbation renormalization group (LPRG). Depending on the parameter set, such a model exhibits one antiferromagnetic (AF) or ferromagnetic (FM) phase transition or three phase transitions with a re-entrant disordered phase between AF and FM ones. The LPRG method was also used to study coupled uniaxial XXZ chains which, for example, can be a minimal model to describe the magnetic properties of compounds in which uranium and rare earth atoms form zig-zag chains. As with the Ising model, for a certain set of parameters, the model can undergo three phase transitions. However, both intrachain and interchain plain interactions si,jxsk,lx+si,jysk,ly can eliminate the re-entrant disordered phase, and then only one transition takes place. Additionally, the XXZ model can undergo temperature-induced metamagnetic transition.

Combined experimental and theoretical studies of some uranium(VI) complexes derived from imidazole-based carbenes

A series of bidentate, viz., 1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazoline-2,2'-diylidene (L1), 1-methyl-3-(2-pyridylmethyl)-imidazoline-2-ylidene (L2) and tridentate, viz., 1,3-bis(2-pyridyl)-imidazoline-2-ylidene (L3) ligands have been obtained from their corresponding imidazolium salts through deprotonation reactions. Treatment of UO2Cl2(THF)3 with one equivalent L3 produces air-stable U(VI)-carbene complex 3, characterized by elemental analysis, FTIR, NMR spectroscopy as well as extended X-ray absorption fine structure (EXAFS) analysis. EXAFS result indicates that the ligand is bonded through one C and two N-atoms to the uranium atom. Attempts to synthesize uranyl complexes derived from L1 and L2 were also successful but these complexes are decomposed quickly within one hour at room temperature. 3 produces pure UO2 powder when heated under an argon atmosphere from room temperature to 600 °C with constant heating rate of 5 °C/min. The solid-state UV–Vis spectrum of the compound shows absorption peaks at 332 and 450 nm. The excitation spectrum of 3 (at λ em = 520 nm) exhibits two almost symmetrical peaks at 273 and 368 nm. Density functional theory-based quantum mechanical calculations indicate that a partial covalent interaction exists between the carbene C and U while a weak non-covalent interaction exists between carbene N and U atoms.

Elastic Cross Section for the Reactions 235U(n, n) and 238U(n, n) at Low Energies Using Woods-Saxon and Coulomb Potentials

The elastic cross section for neutrons by Uranium atoms is calculated for the reactions 235U(n, n) and 238U(n, n) in the regime of low energies using Coulomb andWoods-Saxon potentials. The parameters used in the calculations were chosen by comparison with experimental data previously published by reducing chi-square. Using the same parameters in the equations the ratio 238U/235U is calculated. The results are shown next to the experimental data to illustrate the agreement of the model in the range of energies from 1.5 keV to 1.0 MeV .

Laser-Induced Thermal Decomposition of Uranium Coordination Compounds with Non-oxidic Ligands to Produce Nitride and Carbide Materials.

The production of ceramics from uranium coordination compounds can be achieved through thermal processing if an excess amount of the desired atoms (i.e., C or N), or reactive gaseous products (e.g., methane or nitrogen oxide) is made available to the reactive uranium metal core via decomposition/fragmentation of the surrounding ligand groups. Here, computational thermodynamic approaches were utilized to identify the temperatures necessary to produce uranium metal from some starting compounds─UI4(TMEDA)2, UCl4(TMEDA)2, UCl3(pyridine)x, and UI3(pyridine)4. Experimentally, precursors were irradiated by a laser under various gaseous environments (argon, nitrogen, and methane) creating extreme reaction conditions (i.e., fast heating, high temperature profile >2000 °C, and rapid cooling). Despite the fast dynamics associated with laser irradiation, the central uranium atom reacted with the thermal decomposition products of the ligands yielding uranium ceramics. Residual gas analysis identified vaporized products from the laser irradiation, and the final ceramic products were characterized by powder X-ray diffraction. The composition of the uranium precursor as well as the gaseous environment had a direct impact on the production of the final phases.

Thermal conductivity suppression in uranium-doped thorium dioxide due to phonon-spin interactions

In this work, impact of low level of uranium (U) atom substitution on thermal conductivity of thorium dioxide (ThO2) is investigated. ThO2 is an electronic insulator with a wide optical band-gap and no unpaired electrons whose thermal transport is governed by phonons. U-substitution introduces unpaired f-electrons resulting in paramagnetic behavior of UThO2 at room temperature, which significantly suppresses its thermal conductivity. A single crystal of UThO2 with graded composition of U is grown using a hydrothermal synthesis method, and thermal conductivity measurements are performed in regions with uniform composition of U at levels of 0%, 6%, 9% and 16%. Measured thermal conductivity profiles over 77–300 K temperature range are analyzed using an analytical expression for phonon-mediated thermal transport based on Klemens-Callaway model. Temperature dependent thermal conductivity is found to deviate significantly from the Rayleigh scattering trend expected for a simple substitutional point defect with a small perturbation to mass and interatomic forces. With the resonant scattering term, observed large suppression of thermal conductivity at low temperatures can be closely reproduced. Additionally, the extracted phonon-spin coupling constants imply a nonlinear relation of phonon-spin interaction intensity with respect to U doping percentage. Our study reveals how phonon-spin scattering contributed by unpaired f-electrons in U atoms influences thermal transport in the UThO2 system.

Prediction of novel ordered phases in U-X (X= Zr, Sc, Ti, V, Cr, Y, Nb, Mo, Hf, Ta, W) binary alloys under high pressure

U-based binary alloys have been widely adopted in fast nuclear reactors, but their stability under extreme conditions of high-pressure is almost unknown, mounting up to latent risk in applications. Here, possible ordered phases in U-Zr system up to 200 GPa are comprehensively investigated by unbiased first-principles structure prediction. Stable U2Zr, metastable U3Zr and U4Zr phases are discovered for the first time, which exhibit strong stability under compression. They all are metallic, with 5f electrons of uranium dominating the electronic density of states near the Fermi level. Prominent ionic interactions between U and Zr atoms, as well as covalent interactions between adjacent uranium atoms, are found. The same strategy is applied to explore the stability of ordered phases in other U-based binary transition metal alloys, U-X (X= Sc, Ti, V, Cr, Y, Nb, Mo, Hf, Ta, W). Stable and metastable ordered phases similar to U-Zr alloy are unveiled, all with similar electronic structures. For these alloys, we find that the structure of U2X (X=Zr, Ti, Hf) hosts a unique hybrid phase transition similar to U2Nb, which is a superposition of a first-order transition and a second-order transition. The prediction of these novel phases not only refutes the stability of the long-believed ordered phase I4/mmm-U2Mo, but also rewrites the phase diagrams of U-X (X= Zr, Sc, Ti, V, Cr, Nb, Mo, Hf, Ta) alloys under high pressure. All of these findings promote our understanding of the high-pressure behavior of the broad category of U-based binary alloys with transition metals.

Pressure-induced phase transition, its mechanism and compressibility studies on nanocrystalline and bulk U3O8

High Pressure X-Ray Diffraction (HPXRD) studies were conducted on powder samples of U3O8 with crystallite sizes of 54 nm, 82 nm, as well as bulk U3O8. The investigation revealed that U3O8 undergoes a phase transition to a fluorite phase through an intermediate tetragonal structure, with the (200) plane of the orthorhombic structure playing a pivotal role. This transition occurs through the movement of uranium atoms while maintaining the overall integrity of the lattice. The phase transition is sluggish, and an extensive coexistence regime of the ambient and High-Pressure (HP) fluorite phase is observed in nano form as compared to bulk- U3O8. Moreover, the ambient phase of nano- U3O8 exhibits an elevated bulk modulus of 92 GPa, in contrast to the bulk sample's modulus of 78 GPa. Similarly, for the high-pressure phase, the bulk modulus is 419 GPa for nano- U3O8 and 367 GPa for bulk- U3O8. These findings provide valuable insights into the phase behavior and compressibility of U3O8, thereby carrying potential implications for nuclear technologists.

Temperature Dependence of Nuclear Quadrupole Resonance and the Observation of Metal-Ligand Covalency in Actinide Complexes: 35Cl in Cs2UO2Cl4.

We report a study of the temperature dependence of 35Cl nuclear quadrupole resonance (NQR) transition energies and spin-lattice relaxation times (T1) for 235U-depleted dicesium uranyl tetrachloride (Cs2UO2Cl4) aimed at elucidating electronic interactions between the uranium center and atoms in the equatorial plane of the UO22+ ion. The transition frequency decreases slowly with temperature below 75 K and with a more rapid linear dependence above this temperature. The spin-lattice relaxation time becomes shorter with temperature, and as temperatures increase, the T1 decrease becomes nearly quadratic. The observed trends are reproduced by a model that assumes phonon-induced fluctuations of the electric field gradient tensor and partial electron delocalization from Cl to U. The fit of the theoretical model to experimental data allows a Debye temperature of 96 K to be estimated. The generalization of this approach to investigations of covalency in actinide-ligand bonding is examined.

Uranium-anchored carbon nanotube-based hybrid nanostructure: A promising electrode material for high-performance ultracapacitors

The search for nanomaterials that can offer outstanding electrochemical performances is accelerating due to the rise in demand for reliable energy storage systems. However, the body of knowledge on highly effective radioactive materials, like uranium, is still lacking. Herein, a straightforward fabrication procedure was implemented to fabricate Uranium-based hybrid electrode material, so-called uranium anchored-carbon nanotube (U-CNTx; where x represents the CNT:U ratio by weight) to be employed in ultracapacitors. A radioactive compound-based ultracapacitor cell was made for the first time, to the best knowledge of the researcher, in the rapidly developing field of energy storage devices. The physicochemical features of the fabricated U-CNTx hybrid nanostructures were examined by several characterization techniques including scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), Raman spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and the successful anchoring of the Uranium atoms on CNT architecture was confirmed as well as the morphological characteristics of the structure. With a 96.13% capacitance retention value, after 15,000 consecutive galvanostatic charge-discharge (GCD) cycles at 1.0 A g−1 in addition to a considerable specific capacitance value of 251.8 F g−1 even at a high current density value of 10.0 A g−1, the U-CNT10 electrode-based ultracapacitor cell provided the best performance parameters. The radiation doses of the assembled ultracapacitor cells were measured by a Geiger-Müller detector. The results offered that even the U-CNT10 electrode-based SC, which had the highest uranium content, had no harmful effects on human health or the environment considering its value of ∼0.1–0.3 μSv (excluded background measurement). The development of a high-performance ultracapacitor with uranium-based hybrid organic electrodes may open a new age as a result of this work.

Uranium-based electrode material for the high-performance supercapacitors

In recent decades, significant progress has been made in the engineering of electrode materials for supercapacitors. In this regard, the primary emphasis has been on investigating carbonaceous based materials. However, this focus has restricted the overall capacitance of supercapacitor devices, thus hindering their broader application possibilities. There is still a gap in the literature on high-performance radioactive element-based electrode materials. Bearing this, in this work, a simple approach was suggested for the implementation of uranium, as a radioactive element, decorating onto carbon architecture, as electrode material in high-energy supercapacitor cells. Herein, a facile pathway for tailoring a uranium-decorated graphene oxide nanostructure (U-GOx; where x stands for the GO:U ratio by weight) was proposed and the potential applications of the synthesized nanoarchitectures as an electrode material of supercapacitor cell were investigated. As per the author's knowledge, for the first time in the ever-burgeoning field of energy storage systems, a radioactive compound-based supercapacitor cell was fabricated. The physicochemical characterizations confirmed the successful anchoring of uranium atoms onto the graphene oxide skeleton. The U-GO5 electrode-based-supercapacitor cell offered the highest performance metrics with a 95.92 % capacitance retention value at the end of the 15,000 consecutive galvanostatic charge-discharge cycles, besides the high specific capacitance value of 258.6 F⸱g−1 at a high current density value of 10.0 A⸱g−1. Moreover, the radioactivity measurements were conducted to investigate whether the fabricated supercapacitors were radioactive or not. The results revealed that the measured radiation dose of the U-GO5-based supercapacitor cell before the GCD cycles, which was of the highest uranium content, was ca.0.06 μSv (the background measurement was excluded). This finding indicated there would be no adverse effect on human health or the environment. It can be speculated that this work is a new era for engineering a high-performance supercapacitor based on organic electrodes decorated with a radioactive element.

Structures and stabilities of UPbn (n ≤ 18) clusters: A first-principles global optimization calculation

Endohedrally doped clusters have received much attention because they can act as superatoms and have great potential as the building blocks for cluster-assembled materials. We have carried out a comprehensive study based on the combination of the particle swarming optimization algorithm and the relativistic density functional theory, to obtain geometric structures and stabilities of lead (Pb) clusters doped with one uranium (U) atom. A gradual evolution pattern was observed with the increasing number of Pb atoms, from exohedrally doped structures to quasi-endohedral structures, and finally to endohedrally doped structures. At least 12 and 11 Pb atoms were necessary to encapsulate the U atom completely in the calculation without and with the spin-orbit coupling (SOC) effect respectively. The UPb16 cluster was represented as a highly stable endohedral cage structure with the U atom around its center. In addition, the crucial role of the SOC effect was emphasized. We hope that our findings will provide a fundamental understanding of actinide-doped lead clusters, which may be quite different from their light element analogues.

Three-dimensional charge density wave in the dual heavy fermion system UPt2Si2

Heavy fermion liquids offer via their Kondo lattice diverse possibilities for exotic ground states. Using variable-temperature atomic pair distribution function analysis, we study the local atomic structure of the ``dual'' heavy fermion liquid $\mathrm{U}{\mathrm{Pt}}_{2}{\mathrm{Si}}_{2}$, which exhibits antiferromagnetism consistent with localized $5f$-electron states and transport properties characteristic to itinerant $5f$-``$spd$'' hybridized electron systems. We show that $\mathrm{U}{\mathrm{Pt}}_{2}{\mathrm{Si}}_{2}$ exhibits periodic lattice distortions (PLDs) involving both uranium and platinum atoms that are characteristic to three-dimensional charge density waves. The temperature evolution of the PLDs tracks that of the transport and magnetic properties, suggesting the presence of little-known $5f$-electron-lattice interactions. We argue that PLDs in heavy fermion liquids in general, and in particular in $\mathrm{U}{\mathrm{Pt}}_{2}{\mathrm{Si}}_{2}$, appear as new degrees of freedom that entangle competing electronic states and, as such, must be accounted for when their rich physics is considered.

Adsorption properties of black phosphorene for actinides U, Th, and Pu: A first‐principles study

AbstractDensity functional theory (DFT) calculations were carried out in this work to systematically investigate the adsorption properties of monolayer black phosphorene (BP) for actinide uranium (U), thorium (Th), and plutonium (Pu) atoms. More specifically, the linear response method was used and the HubbardUvalues of 2.97 and 2.61 eV were fitted describing the strong lattice point Coulomb interactions of the U and Pu 5forbitals, respectively. From the DFT + Ucalculations, it was demonstrated that the U, Th, and Pu atoms can be favorably adsorbed on the hollow sites of the BP surface, with an adsorption energy of 3.48, 4.93, and 0.98 eV, respectively. By analyzing the electronic structure, charge transfer, and highest occupied molecular orbital, it was revealed that the U and Th adatoms can induce the generation of impurity states within the band gap of BP and stabilize their adsorption by strongp‐dcoupling with the phosphorus atoms. In addition, from the electron–phonon coupling calculations, it was revealed that the temperature for the stable adsorption of the U and Th adatoms can reach as high as 500 and 673 K. By using the adsorption rate equation, the critical temperature for the adsorption–desorption transition of U and Pu adatoms was estimated to be 632 and 185 K, respectively, while the Th adatom did not tend to desorb. Our results clearly indicate that BP is an ideal adsorption and separation material for actinides with promising potential applications, such as uranium extraction from seawater.