4f States Research Articles

Gd impurities effect on $$\hbox {Co}_{2}\hbox {CrSi}$$ Co 2 CrSi alloy: first-principle calculations

First-principle calculations have been performed to study Gd impurities doping effect on the physical properties of the Heusler half-metallic ferromagnet \(\hbox {Co}_{2}\hbox {CrSi}\) using the density functional theory in the local spin density approximation with an additional Hubbard correlation term for the rare-earth 4f states. The results show that the gadolinium moment is aligned antiparallel to that of transition metal atoms for both \(\hbox {Co}_{16} \hbox {Cr}_{7} \hbox {GdSi}_{8}\) and \(\hbox {Co}_{15}\hbox {GdCr}_{8}\hbox {Si}_{8}\). The analysis of the doped material band structures shows that the half-metallic properties are completely conserved if Gd substitutes Cr atoms, while the minority-spin gap is filled and half-metallicity is lost when Gd substitutes Co atoms.

First-principle calculations of crystal structures, electronic structures, and optical properties of RETaO4 (RE = Y, La, Sm, Eu, Dy, Er)

It is an effective method to protect components from high power laser damage using high reflective materials. The rare earth tantalates RETaO4 with high dielectric constant suggests that they may have very high reflectivity, according to the relationship between dielectric constant and reflectivity. The crystal structures, electronic structures, and optical properties of RETaO4 (RE=Y, La, Sm, Eu, Dy, Er) have been studied by first-principle calculations. With the increasing atomic number of RE (i.e., the number of 4f electrons), a 4f electron shell moves from the bottom of conduction band to the forbidden gap and then to the valence band. The relationship between the electronic structures and optical properties is explored. The electron transitions among O 2p states, RE 4f states, and Ta 5d states have a key effect on optical properties such as dielectric function, absorption coefficient, and reflectivity. For the series of RETaO4, the appearance of the 4f electronic states will obviously promote the improvement of reflectivity. When the 4f states appear at the middle of the forbidden gap, the reflectivity reaches the maximum. The reflectivity of EuTaO4 at 1064 nm is up to 93.47%, indicating that it has potential applications in the antilaser radiation area.

Room-temperature synthesis and photoluminescence of hexagonal CePO4 nanorods

Hexagonal CePO4 nanorods were synthesized via a simple chemical precipitation route at room-temperature without the presence of surfactants and then characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV–vis) absorption and photoluminescence (PL) spectroscopy. Hexagonal CePO4 nanorods exhibit strong ultraviolet absorption and ultraviolet luminescence, which correspond to the electronic transitions between 4f and 5d state of Ce3+ ions.

Ln3+ 4f Energy Levels in CaTiO3 Analyzed by XPS Measurements

The energy levels of Ln3+ 4f ground states in CaTiO3 are analyzed using X‐ray photoelectron spectroscopy (XPS). The Ln 4f states in the XPS spectra are extracted utilizing large photoionization cross section differences between Ln 4f and O 2p states. The Ln3+ 4f energy levels referred to the valence band maximum are evaluated to be 0.8 eV for Pr3+, −5.0 eV for Gd3+, 0.9 eV for Tb3+, and −4.6 eV for Lu3+ from the extracted XPS spectra. Although the obtained values of Gd3+ and Lu3+ 4f levels are deeper in the valence band, the values of Pr3+ and Tb3+ 4f levels are in good agreement with those reported previously. The difference in the photoluminescence colors between Pr3+‐doped CaTiO3 and CaZrO3 is simply explained from the Pr3+ 4f energy levels located in the bandgaps.

First principle investigations of the Pbnm phase BiFeO3, BiFe0.875Mn0.125O3 and Bi0.875X0.125Fe0.875Mn0.125O3 (XBFM) (X = Ce, Gd, Lu)

The structural, magnetic, electronic and optical properties of Pbnm BiFeO[Formula: see text] (BFO), BiFe[Formula: see text]Mn[Formula: see text]O[Formula: see text] (BFM), Bi[Formula: see text]X[Formula: see text]Fe[Formula: see text]Mn[Formula: see text]O[Formula: see text] (XBFM) (X = Ce, Gd, Lu) have been investigated by the first principles within the PBE[Formula: see text]+[Formula: see text]U scheme. It is shown that the dopant Mn in the B sites and Ce (Gd, Lu) in the A sites improves the crystalline quality. The magnetic moments of Bi[Formula: see text]Ce[Formula: see text]Fe[Formula: see text]Mn[Formula: see text]O[Formula: see text] (CBFM) and Bi[Formula: see text]Gd[Formula: see text]Fe[Formula: see text]Mn[Formula: see text]O[Formula: see text] (GBFM) are 10 [Formula: see text] and 16 [Formula: see text] which mainly arises from the strongly localized unpaired 4f electrons of Ce and Gd, 3d electrons of Mn and Fe. While, as BFM, the magnetic moment of Bi[Formula: see text]Lu[Formula: see text]Fe[Formula: see text]Mn[Formula: see text]O[Formula: see text] (LBFM) is 9 [Formula: see text] indicating no effect on the magnetization is made by Lu for its full 4f states. The densities of states of the five systems hint that CBFM is metallic and BFM, GBFM, LBFM are still semiconductors. The metallic properties of CBFM arise from the hybridization between Ce-4f and Mn-3d states which leads the Mn [Formula: see text] states to be split into [Formula: see text] and [Formula: see text] lowering the bottom of the conduction band to cross the Fermi level. Furthermore, we also study the optical properties of Pbnm BiFeO[Formula: see text] (BFO), BiFe[Formula: see text]Mn[Formula: see text]O[Formula: see text] (BFM), Bi[Formula: see text]X[Formula: see text]Fe[Formula: see text]Mn[Formula: see text]O[Formula: see text] (XBFM) (X = Ce, Gd, Lu). In this work, the optical properties including the absorption spectrum, loss function, refractive index and reflectivity spectrum are discussed in detail.

Manifestation of intra-atomic 5d6s-4f exchange coupling in photoexcited gadolinium

Intra-atomic exchange couplings (IECs) between 5d6s and 4f electrons are ubiquitous in rare-earth metals and play a critical role in spin dynamics. However, detecting them in real time domain has been difficult. Here we show the direct evidence of IEC between 5d6s and 4f electrons in gadolinium. Upon femtosecond laser excitation, 5d6s electrons are directly excited; their majority bands shift toward the Fermi level while their minority bands do the opposite. For the first time, our first-principles minority shift now agrees with the experiment quantitatively. Excited 5d6s electrons lower the exchange potential barrier for 4f electrons, so the 4f states are also shifted in energy, a prediction that can be tested experimentally. Although a significant number of 5d6s electrons, some several eV below the Fermi level, are excited out of the Fermi sea, there is no change in the 4f states, a clear manifestation of intra-atomic exchange coupling.

Surface characterization of U(AlxSi1-x)3 alloy and its interaction with O2 and H2O, at room temperature

Surface characterization and the interactions of U(AlxSi1-x)3 alloy (x = 0.57) with oxygen and water vapor were studied, utilizing X-Ray Photoelectron Spectroscopy and Direct Recoil Spectrometry, at room temperature. The U 4f spectrum of U(AlxSi1-x)3 alloy exhibits weak correlation satellites, suggesting an itinerant description of the U 5f states for this compound. The Al and Si 2p lines are chemically shifted to lower binding energies. Exposing the alloy to oxygen and water vapor results in oxidation of mainly the uranium and aluminum components, while silicon is only slightly oxidized. Oxygen was found to be a stronger oxidizer than water vapor and the trend is consistent with the more negative enthalpies of formation of metal oxides produced by the O2 reaction, as compared to H2O. During oxygen exposure, fast oxidation occurs by oxide islands nucleation and lateral growth, followed by oxidation of the sub-surface, up to ∼4 nm, at 1000 L exposure. Water initially reacts with the surface by full dissociation and oxide islands formation, which is then covered by hydroxides. Only a minor increase in the oxide thickness of up to ∼2.5 nm, was observed after coalescence.

Unraveling 5f-6d hybridization in uranium compounds via spin-resolved L-edge spectroscopy

The multifaceted character of 5f electrons in actinide materials, from localized to itinerant and in between, together with their complex interactions with 6d and other conduction electron states, has thwarted efforts for fully understanding this class of compounds. While theoretical efforts abound, direct experimental probes of relevant electronic states and their hybridization are limited. Here we exploit the presence of sizable quadrupolar and dipolar contributions in the uranium L3-edge X-ray absorption cross section to provide unique information on the extent of spin-polarized hybridization between 5f and 6d electronic states by means of X-ray magnetic circular dichroism. As a result, we show how this 5f-6d hybridization regulates the magnetism of each sublattice in UCu2Si2 and UMn2Si2 compounds, demonstrating the potentiality of this methodology to investigate a plethora of magnetic actinide compounds.

Synthesis, spectroscopy, and efficient laser operation of “mixed” sesquioxide Tm:(Lu,Sc)_2O_3 transparent ceramics

A novel transparent 4.76 at.% Tm:(Lu2/3Sc1/3)2O3 “mixed” sequioxide ceramic is synthesized by hot isostatic pressing (HIP) at 1800 °C / 195 MPa in an Ar atmosphere. Its structure is studied by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The spectroscopic properties of the Tm3+ ion are described within the Judd-Ofelt theory, which resulted in intensity parameters of Ω2 = 2.429, Ω4 = 1.078 and Ω6 = 0.653 [10−20 cm2]. For the 3F4 → 3H6 transition, the maximum stimulated-emission cross-section σSE is 7.15 × 10−21 cm2 at 1951 nm. The radiative lifetime of the 3F4 state is 4.01 ms. Under diode-pumping at 802 nm, a microchip Tm:(Lu,Sc)2O3 ceramic laser generated ~1 W at 2100 nm with a slope efficiency of 24%. The spectroscopic and laser properties of the Tm:(Lu,Sc)2O3 ceramic are compared with those of a Tm:LuScO3 single crystal. The ceramic exhibits very broad and flat gain cross sections, which is promising for ultrashort pulse generation.

Electronic and Magnetic Investigations of Rare-Earth Tm-doped AlGaN Ternary Alloy

Electronic structure and magnetic interaction of substitutional thulium rare earth-doped wurtzite Al0.5Ga0.5N ternary alloy have been performed using density-functional theory within local spin-density approximation with Hubbard-U corrections (LSDA+U) approach. The LSDA+U method is applied to the rare earth (RE) 4f states. The calculation of formation energy shows that it is more energetically favorable for a substitutional Tm atom to replace the Al atom than the Ga atom. For AlGaN:Tm, the lattices parameters are expanded due to larger ionic radius of Tm than that of Al atoms. The energy band gap of AlGaN:Tm has direct character and its width becomes small compared with that of AlGaN. The magnetic coupling between Tm ions in the nearest neighbor sites is ferromagnetic. Magnetic interaction of rare earth ion with the host states at the valence and conduction band edges has been investigated and compared to those of GaN:Mn and has been found to be relatively small.

Rare earth ions doped K2Ta2O6 photocatalysts with enhanced UV–vis light activity

Novel rare earth-doped K2Ta2O6 (RE-K2Ta2O6) photocatalysts were successfully synthesized by one-step hydrothermal method. The effect of dopant type (RE=Y, Yb, Ho, Pr, Er) and amount of rare earth precursor (2, 4, 8 and 10mol%) on the physicochemical and photocatalytic properties of RE-K2Ta2O6 have been investigated. All as-prepared materials were subsequently characterized by UV–vis diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) specific surface area measurement, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, mass magnetic susceptometry and photoluminescence (PL) emission spectroscopy. The photocatalytic activity under UV–vis light irradiation was estimated in phenol degradation in aqueous phase, toluene removal in gas phase and H2 generation from formic acid solution. The experimental results show that, novel RE-K2Ta2O6 exhibits greatly improved degradation efficiency under UV–vis light irradiation compared with pristine K2Ta2O6. The Er-K2Ta2O6 and Pr-K2Ta2O6, obtained by introducing of 2mol% of RE ions during synthesis, reveal the highest photocatalytic activity among prepared samples in aqueous phase (33% of phenol decomposition after 90min of irradiation) and gas phase (45% of toluene removal after 60min of irradiation), respectively. Moreover, both photocatalysts present good stability after subsequent three cycles. The active species trapping test shows that OH and O2− radicals are significantly involved in phenol oxidation under UV–vis light irradiation. The amount of H2 evolution increases with increasing addition of Er dopant into K2Ta2O6 lattice. The highest H2 production is obtained for 10mol% Er-K2Ta2O6 after 240min of UV–vis light irradiation (15.40μmol/min). Enhanced photoactivity performance can be attributed to incorporation of RE ions at K+ lattice site in RE-K2Ta2O6, probably leading to formation of new RE 4f states below the conduction band of K2Ta2O6 structure. To investigate the localization of RE ions in K2Ta2O6 structure, the band structure and partial density of the states (PDOS) have been investigated. Computer simulations were performed using plane-wave based Vienna ab-initio simulation package (VASP) with the generalized gradient approximation (GGA) by Perdew-Burke-Ernzerhof (PBE). Moreover, inclusion of RE ions in K2Ta2O6 causes predominance pyrochlore phase formation over perovskite in regular cubic structure. Summarized, RE-doped K2Ta2O6 is promising material in photocatalytic degradation of organic pollutants and H2 generation processes. Our work may provide valuable information for rare earth doping semiconductor with improved photocatalytic performance.

Low temperature thermopower and magnetoresistance of Sc-rich CeSc1-xTixGe

In CeSc1-xTixGe, Ti-alloying reduces the record-high antiferromagnetic (AFM) ordering temperature found in CeScGe at TN=46K and induces ferromagnetism for x≥0.5. In this work we focus on the AFM side, i.e. Sc-rich samples, and study their thermopower S(T) and magnetoresistance ρ(H,T). The measured S(T) is small in comparison with the thermopower of other Ce-systems and shows some features that are compatible with a weak hybridization between the 4f and band states. This is a further hint pointing to the local character of magnetism in this alloy. Magnetic fields up to 16T have a minor effect on the electrical resistivity of stoichiometric CeScGe. On the other hand, for x=0.65, we find that fields above 4T suppress the hump in ρ(T). Furthermore, the 4.2K magnetoresistance displays a strong decrease in the same field range, also in coincidence with magnetization results from the literature. Our results indicate that ρ(T,H) is a proper tool to assess the H−T phase diagram of this system.

Novel gas sensor with dual response under CO(g) exposure: Optical and electrical stimuli

In this work, a lanthanum (La) doped ceria (CeO2) film, which depicted a dual gas sensing response (electric and optical) for CO(g) detection, was obtained by the microwave-assisted hydrothermal (HAM) synthesis and deposited by the screen-printing technique, in order to prevent deaths by intoxication with this life-threatening gas. An electric response under CO(g) exposure was obtained, along with an extremely fast optical response for a temperature of 380 °C, associated with Ce+4 reduction and vacancy generation. A direct optical gap was found to be around 2.31 eV from UV–Vis results, which corresponds to a transition from valence band to 4f states. Due to the anomalous electron configuration of cerium atoms with 4f electrons in its reduced state, they are likely to present an electric conduction based on the small polaron theory with a hopping mechanism responsible for its dual sensing response with a complete reversible behaviour.

Lifshitz transition from valence fluctuations in YbAl3

In mixed-valent Kondo lattice systems, such as YbAl3, interactions between localized and delocalized electrons can lead to fluctuations between two different valence configurations with changing temperature or pressure. The impact of this change on the momentum-space electronic structure is essential for understanding their emergent properties, but has remained enigmatic. Here, by employing a combination of molecular beam epitaxy and in situ angle-resolved photoemission spectroscopy we show that valence fluctuations can lead to dramatic changes in the Fermi surface topology, even resulting in a Lifshitz transition. As the temperature is lowered, a small electron pocket in YbAl3 becomes completely unoccupied while the low-energy ytterbium (Yb) 4f states become increasingly itinerant, acquiring additional spectral weight, longer lifetimes, and well-defined dispersions. Our work presents a unified picture of how local valence fluctuations connect to momentum-space concepts such as band filling and Fermi surface topology in mixed valence systems.

Magnetic structure in a U(Ru0.92Rh0.08)2Si2 single crystal studied by neutron diffraction in static magnetic fields up to 24 T

We report the high-field induced magnetic phase in single crystal of U(Ru0.92Rh0.08)2Si2. Our neutron study combined with high-field magnetization, shows that the magnetic phase above the first metamagnetic transition at Hc1 = 21.6 T has an uncompensated commensurate antiferromagnetic structure with propagation vector Q2 = ( 2/3 0 0) possessing two single-Q domains. U moments of 1.45 (9) muB directed along the c axis are arranged in an up-up-down sequence propagating along the a axis, in agreement with bulk measurements. The U magnetic form factor at high fields is consistent with both the U3+ and U4+ type. The low field short-range order that emerges from the pure URu2Si2 due to Rh-doping is initially strengthened by the field but disappears in the field-induced phase. The tetragonal symmetry is preserved across the transition but the a axis lattice parameter increases already at low fields. Our results are in agreement with itinerant electron model with 5f states forming bands pinned in the vicinity of the Fermi surface that is significantly reconstructed by the applied magnetic field.

(Invited) Studies of Luminescence Efficiency of BaWO4:Ce Crystals

Barium tungstate crystals are interesting and relatively new medium for stimulated Raman scattering for applications in Raman shifters of laser radiation [1]. Good quality BaWO4 crystals can be grown by Czochralski technique and doped with rare-earth ions. Doping with trivalent ions require charge compensation which may be provided, for example, by structural defects or proper codoping with alkaline metal ions. Crystals posses sheelite structure with the space group I41/a. Results of studies of BaWO4:Ce crystals and crystals codoped with Na are presented in this work. Optical absorption in the vis-UV and infrared range and Raman spectra has been studied. In the UV the crystals shows typical absorption for Ce3+ with two bands peaked at 320 nm and 285 nm, which are associated with lowest energy 4f-5d transitions. However only very weak Ce3+ luminescence is observed even at 10 K, contrary to some reports on this subject [2]. In the mid-infrared range several absorption bands are visible which may be associated with lattice absorption. Besides of lines associated with single TO phonon modes in the range up to 1000 cm-1 the additional lines appear around 1700 cm-1 and 2600 cm-1. Origin of these lines is discussed in this work. Raman spectra at room temperature show very sharp lines with the highest energy line at 927 cm-1. Some additional much broader lines are observed above 1200 cm-1 [3]. Their origin is most probably associated with combination of various phonon modes. In addition to that very sharp lines due to the 4f-4f transitions in the Ce3+ ions are visible around 2200 cm-1 and 2350 cm-1. There are at least four of these lines in each group which are related to the multisite structure of RE doping in these crystals. The crystal field analysis allows identifying nature of these lines. The transitions associated with Ce3+ ions are very strongly coupled with the lattice and they undergo very important broadening with increase of temperature. This is explained as a result of electron-phonon coupling, enhanced by the matching inter-level spacing of the 2F7/2 state with phonon energies. BaWO4 has the largest energy gap among several tungstates with scheelite structure [4]. It is in good agreement with the values of ionic radii of cations constituting the host. The conduction band is dominated by the W6+ 5d states. On the other hand the luminescence efficiency of Ce3+ dopand in BaWO4 is the lowest among the (Ca, Sr,­ Ba)WO­4, which have smaller band-gap than BaWO4. It may be associated with resonant position of the lowest 5d state of Ce3+ in the conduction band or with the thermally activated crossover between the 4f 5d state and the 4f states. The large band gap of BaWO4 rather shows that the latter mechanism is operative as the luminescence quenching mechanism. High pressure luminescence studies in diamond anvil cell, which should help to resolve this question will be presented in this work. Acknowledgements: This work was supported by the Polish National Science Center (project 2015/17/B/ST5/01658)

Combining electronic structure and many-body theory with large databases: A method for predicting the nature of 4f states in Ce compounds

Here we present the first large scale investigation of electronic properties and correlated magnetism in Ce-based compounds accompanied by a systematic study of the electronic structure and 4f-hybridization function of a large body of Ce compounds. We systematically study the electronic structure and 4f-hybridization function of a large body of Ce compounds with the goal of elucidating the nature of the 4f states and their interrelation with the measured Kondo energy in these compounds. The hybridization function has been analyzed for more than 350 data sets of cubic Ce compounds using electronic structure theory that relies on a full-potential approach. We demonstrate that the strength of the hybridization function, evaluated in this way, allows us to draw precise conclusions about the degree of localization of the 4f states in these compounds. The theoretical results are entirely consistent with all experimental information, relevant to the degree of 4f localization for all investigated materials. Furthermore, a more detailed analysis of the electronic structure and the hybridization function allows us to make precise statements about Kondo correlations in these systems. The calculated hybridization functions, together with the corresponding density of states, reproduce the expected exponential behavior of the observed Kondo temperatures and prove a consistent trend in real materials. This trend allows us to predict which systems may be correctly identified as Kondo systems. A strong anti-correlation between the size of the hybridization function and the volume of the systems has been observed. Our approach demonstrates the predictive power of materials informatics when a large number of materials is used to establish significant trends which can be used to design new materials with desired properties.

Color-tunable luminescence and energy transfer properties of Dy3+/Eu3+ codoped Sr3Sc(PO4)3 eulytite-type orthophosphate phosphors for NUV-LEDs

A series of single-phase and color-tunable Dy3+, Eu3+ singly doped and Dy3+/Eu3+ co-doped Sr3Sc(PO4)3 phosphors have been synthesized via a solid-state reaction method. The crystal structure, phase and constitution of the prepared phosphors were investigated using X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX). The excitation and emission spectra, the powder diffuse reflectance spectra (DRS) and fluorescence decays were measured and discussed. The results revealed that Dy3+ can efficiently transfer excitation energy to Eu3+ via its 4f states and therefore sensitized Eu3+ emission under near-ultraviolet (NUV) excitation. Meanwhile, the energy transfer mechanism could be ascribed to be electric dipole–dipole interaction, which can be validated via the linear fitting of the relationship (IS0/IS)∝Cn/3. The Commission Internationale deL’Eclairage (CIE) chromaticity coordinates of the phosphors can be tuned from wathet blue (0.2509, 0.2149) to light orange (0.4022, 0.2924) by adjusting the ratio of Dy3+ and Eu3+. In addition, the CIE coordinate of Sr3Sc0.89(PO4)3:0.07Dy3+, 0.04Eu3+ phosphor was quite close to (0.333, 0.333), which showed that Sr3Sc(PO4)3:Dy3+, Eu3+ phosphors could be used as NUV excitable white light-emitting phosphors.

Characteristics of thulium doped gallium oxide films grown by pulsed laser deposition

Thulium (Tm) doped Ga2O3 films were deposited on sapphire substrates by pulsed laser deposition (PLD) with changing Tm compositions in the targets. Energy dispersive spectroscopy results reveal that films with different Tm compositions can be tailored by changing the Tm composition in the targets. X-ray diffraction and Raman spectra analysis indicate that all films have the monoclinic structure. Photoluminescence measurements demonstrate that the emission peaks at 460, 650 and 800nm are observed from the Tm3+ 4f intrashell transitions from 1G4 excited states to the 3H6, 3F4, and 3H5 states, respectively. The results suggest that PLD is a promising method for obtaining high quality Tm doped Ga2O3 films, which paves the way for the fabrication of optoelectronic devices based on Ga2O3 films.

Influence of Ga on H Reactivity with Ga-Stabilized δ-Pu Alloys

The influence of Ga on the adsorption and solubility of H on Ga-stabilized δ-Pu alloys is investigated using density functional theory and experimentally via a Sieverts’ apparatus. All-electron DFT calculations, with spin–orbit coupling and full relaxations of the surface, are implemented to calculate H adsorption on δ-Pu–Ga alloy (111) surfaces. Chemisorption energies indicate that H prefers a 3-fold hollow site that binds strongly to a Pu-rich environment regardless of Ga concentration of the surface. Sites that include a Ga–H bond yield an increase in chemisorption energies as opposed to chemisorption energies when the H is only bonded to Pu atoms. Also, solution energies for interstitial sites are less exothermic than surface adsorption energies. Experimentally, H-vacancy binding is more exothermic than interstitial binding, and since vacancy binding is the analogue of surface binding, the DFT results are in agreement. Both DFT and experimental results show that with increasing Ga content to 7 at. % Ga there is an increase in H solution energies, thus reducing H solubility. The maximal reduction of H solubility is between 4 and 5 at. % Ga stabilized δ-Pu. The bonding nature of H on the Pu–Ga surface, via analysis of the partial density of states, shows weak hybridizations between the Pu 6d and H 1s states, with a slight decrease of the Pu 5f states near the Fermi level. Overall, Ga will affect the surface adsorption and solubility of H in δ-Pu–Ga alloys.