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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Gd(SiNi5)2 by Materials Project

GdNi10Si2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to sixteen Ni and four equivalent Si atoms. There are a spread of Gd–Ni bond distances ranging from 2.76–3.09 Å. All Gd–Si bond lengths are 3.12 Å. There are four inequivalent Ni sites. In the first Ni site, Ni is bonded in a 2-coordinate geometry to one Gd, eleven Ni, and two equivalent Si atoms. There are a spread of Ni–Ni bond distances ranging from 2.36–2.91 Å. Both Ni–Si bond lengths are 2.53 Å. In the second Ni site, Ni is bonded in a 1-coordinate geometry to one Gd, eleven Ni, and two equivalent Si atoms. There are a spread of Ni–Ni bond distances ranging from 2.42–2.66 Å. Both Ni–Si bond lengths are 2.40 Å. In the third Ni site, Ni is bonded in a 12-coordinate geometry to two equivalent Gd, eight Ni, and two equivalent Si atoms. All Ni–Ni bond lengths are 2.41 Å. Both Ni–Si bond lengths are 2.56 Å. In the fourth Ni site, Ni is bonded to two equivalent Gd, eight Ni, and two equivalent Si atoms to form NiGd2Si2Ni8 cuboctahedra that share corners with four equivalent SiGd2Ni10 cuboctahedra, corners with ten equivalent NiGd2Si2Ni8 cuboctahedra, edges with two equivalent SiGd2Ni10 cuboctahedra, edges with four equivalent NiGd2Si2Ni8 cuboctahedra, faces with four equivalent SiGd2Ni10 cuboctahedra, and faces with six equivalent NiGd2Si2Ni8 cuboctahedra. Both Ni–Ni bond lengths are 2.37 Å. Both Ni–Si bond lengths are 2.31 Å. Si is bonded to two equivalent Gd and ten Ni atoms to form SiGd2Ni10 cuboctahedra that share corners with six equivalent SiGd2Ni10 cuboctahedra, corners with eight equivalent NiGd2Si2Ni8 cuboctahedra, edges with three equivalent SiGd2Ni10 cuboctahedra, edges with four equivalent NiGd2Si2Ni8 cuboctahedra, a faceface with one SiGd2Ni10 cuboctahedra, and faces with eight equivalent NiGd2Si2Ni8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Electrochemical recovery of Gd into liquid Bi in molten LiCl-KCl-GdCl 3

The electrochemical recovery of Gd into liquid Bi electrodes was investigated in molten LiCl-KCl-GdCl 3 electrolyte at 773–973 K using constant currents of 10–150 mA cm −2 . High round-trip coulombic efficiency (>97 %) was demonstrated for deposition and removal of Gd into and from liquid Bi at all temperatures, confirming chemically reversible electrode reactions towards high recovery yield of Gd using liquid Bi. Furthermore, the overpotential associated with deposition of Gd into the liquid Bi electrode gradually increased with current density and decreased with temperature. At the lowest temperature of 773 K, a steep increase in overpotential was evident at high current densities due to slower mass transport and low solubility of Gd in liquid Bi (0.5 at.% Gd). Based on the impedance spectra of Bi electrodes at 773–973 K, the exchange current density was estimated to be 110–220 mA cm −2 , indicating facile charge transfer at the liquid electrode-electrolyte interface. Post-mortem characterization of Bi cathodes after electrolysis at 873 K indicated the formation of a solid GdBi(s) compound layer at the Bi electrode surface. Chemical analysis of Bi cathodes at various deposited Gd compositions resulted in Faradaic efficiencies of ∼75–84 %, promising a high recovery yield of Gd from molten salts using a strongly-interacting liquid Bi electrode.

36 - MATERIALS SCIENCE↗
DOE OSTI2023

Structural Changes to the Gd‐DTPA Complex at Varying Ligand Protonation State

Abstract Diethylenetriaminepentaacetic acid (DTPA) is a chelating agent whose complex with the Gd 3+ ion is used in medical imaging. DTPA is also used in lanthanide‐actinide separation processes. As protonation of the DTPA ligand can facilitate dissociation of the Gd 3+ ion from the Gd‐DTPA complex, this work investigates the coordination structures of the aqueous Gd 3+ ion and its environment when chelated by DTPA in eight different DTPA protonation states. Both classical and ab initio molecular dynamics (MD) simulations are conducted to model the solvated complexes. Extended X‐ray absorption fine structure (EXAFS) measurements of the Gd 3+ aqua ion, and the Gd‐DTPA complex at pH 1 and 11, are compared to EXAFS spectra predicted from the MD simulations to verify the accuracy of the MD structures. The findings of this work provide atomic‐level details into the fluctuating Gd‐DTPA complex environment as the DTPA ligand gradually detaches from the Gd 3+ ion with increased protonation.

Chemistry↗
DOE OSTI2020

The role of low Gd concentrations on magnetisation behaviour in rare earth:transition metal alloy films

The magnetisation reversal behaviour as a function of composition was studied in low rare earth concentration alloys. 30 nm thick rare earth:transition-metal films of composition GdxCo 100-x , GdxFe 100-x and Gd x (Co 50 Fe 50 ) 100-x were prepared by magnetron sputtering, where x ranged from 4 to 13 atomic%. Magnetisation behaviour was studied using MOKE and Hall hysteresis measurements. The magnetic reversal behaviour as a function of Gd content is strongly dependent on the transition metal. With increasing Gd content the film structure transitions from crystalline to amorphous and the saturation magnetisation decreases linearly. For GdCo, the reversal field, Hc, increases by less than a factor of two with Gd doping of 11%, while for Fe, the coercivity falls by a factor of ten with 8% Gd. This may be attributed to changes in the crystalline morphology. GdCoFe shows a similar trend with Gd doping for the in-plane reversal field to that of GdFe. With 13% Gd in Fe there is evidence indicating the presence of a weak perpendicular magnetic anisotropy, PMA. With Gd doping the anomalous Hall resistivity of Co, Fe and CoFe increases significantly with the largest increase observed for GdCoFe.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Coverage-dependent structures and thermodynamic stability of intercalated Gd layers beneath buffer-layer graphene on SiC(0001)

Electronic properties of two-dimensional (2D) materials are strongly influenced by their atomic arrangements, making the theoretically-aided characterization of experimentally-synthesized 2D structures crucial. Using first-principles density functional theory, we analyze nearly 200 configurations of intercalated Gd layers beneath buffer-layer graphene on SiC(0001) over a Gd coverage range of 0.01 < θ < 1.2. By fully relaxing selectively-constructed configurations at each coverage within a large, low-strain supercell, we determine the coverage dependence of the chemical potential for intercalated Gd structures. Thermodynamically-preferred configurations below θ ≈ 0.8 form single-atom-thick monolayers, while 3D-like or multilayer structures emerge beyond θ ≈ 0.9. Most structures are amorphous-like, including the configuration at the chemical potential minimum around θ ≈ 0.4. In contrast, a strongly stretched Gd(0001)-like monolayer at θ = 1/3 and a nearly perfect Gd(0001) monolayer at θ = 1 are significantly less favorable with 0.16 eV and 0.82 eV higher chemical potentials above the minimum, respectively. Furthermore, the graphene layer decoupled by intercalated Gd near the chemical potential minimum is significantly flatter compared to its morphology above intercalated 3D structures at higher coverages and nearly isolated Gd atoms in the lowest coverage region. In conclusion, these findings align with our experimental results and underscore the need for further research on this unique intercalated system, which holds significant potential for diverse applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(Al2Cr)4 by Materials Project

Gd(CrAl2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to eight equivalent Cr and twelve Al atoms. All Gd–Cr bond lengths are 3.41 Å. There are four shorter (3.03 Å) and eight longer (3.21 Å) Gd–Al bond lengths. Cr is bonded to two equivalent Gd, two equivalent Cr, and eight Al atoms to form distorted CrGd2Al8Cr2 cuboctahedra that share corners with eight equivalent AlGd2Al6Cr4 cuboctahedra, corners with ten equivalent CrGd2Al8Cr2 cuboctahedra, edges with four equivalent CrGd2Al8Cr2 cuboctahedra, edges with four equivalent AlGd2Al6Cr4 cuboctahedra, faces with six equivalent CrGd2Al8Cr2 cuboctahedra, and faces with eight equivalent AlGd2Al6Cr4 cuboctahedra. Both Cr–Cr bond lengths are 2.52 Å. There are four shorter (2.58 Å) and four longer (2.69 Å) Cr–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to two equivalent Gd, four equivalent Cr, and six Al atoms to form distorted AlGd2Al6Cr4 cuboctahedra that share corners with eight equivalent CrGd2Al8Cr2 cuboctahedra, corners with ten equivalent AlGd2Al6Cr4 cuboctahedra, edges with three equivalent AlGd2Al6Cr4 cuboctahedra, edges with four equivalent CrGd2Al8Cr2 cuboctahedra, faces with seven equivalent AlGd2Al6Cr4 cuboctahedra, and faces with eight equivalent CrGd2Al8Cr2 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.73–2.88 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to one Gd, four equivalent Cr, and five Al atoms. The Al–Al bond length is 2.90 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(Sn3Ru2)2 by Materials Project

Gd(Ru2Sn3)2 crystallizes in the tetragonal I-42m space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to four equivalent Ru and twelve Sn atoms. All Gd–Ru bond lengths are 3.29 Å. There are a spread of Gd–Sn bond distances ranging from 3.38–3.78 Å. Ru is bonded in a 7-coordinate geometry to one Gd and six Sn atoms. There are a spread of Ru–Sn bond distances ranging from 2.60–2.81 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 6-coordinate geometry to two equivalent Gd and four equivalent Ru atoms. In the second Sn site, Sn is bonded in a 5-coordinate geometry to two equivalent Gd and four equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(SiPt)2 by Materials Project

GdPt2Si2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Gd is bonded in a 4-coordinate geometry to eight Pt and eight Si atoms. There are four shorter (3.21 Å) and four longer (3.30 Å) Gd–Pt bond lengths. There are four shorter (3.21 Å) and four longer (3.23 Å) Gd–Si bond lengths. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 9-coordinate geometry to four equivalent Gd and five Si atoms. There are one shorter (2.41 Å) and four longer (2.44 Å) Pt–Si bond lengths. In the second Pt site, Pt is bonded to four equivalent Gd and four equivalent Si atoms to form a mixture of distorted face and edge-sharing PtGd4Si4 tetrahedra. All Pt–Si bond lengths are 2.49 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to four equivalent Gd and five Pt atoms. In the second Si site, Si is bonded in a 4-coordinate geometry to four equivalent Gd and four equivalent Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(Al2Cu)4 by Materials Project

Gd(CuAl2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to eight equivalent Cu and twelve Al atoms. All Gd–Cu bond lengths are 3.37 Å. There are four shorter (3.06 Å) and eight longer (3.22 Å) Gd–Al bond lengths. Cu is bonded to two equivalent Gd, two equivalent Cu, and eight Al atoms to form a mixture of distorted corner, edge, and face-sharing CuGd2Al8Cu2 cuboctahedra. Both Cu–Cu bond lengths are 2.57 Å. There are four shorter (2.57 Å) and four longer (2.69 Å) Cu–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent Gd, four equivalent Cu, and six Al atoms. There are two shorter (2.74 Å) and four longer (2.81 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 10-coordinate geometry to one Gd, four equivalent Cu, and five Al atoms. The Al–Al bond length is 2.69 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(CuSn)2 by Materials Project

GdCu2Sn2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to eight Cu and eight Sn atoms. There are four shorter (3.34 Å) and four longer (3.39 Å) Gd–Cu bond lengths. There are four shorter (3.32 Å) and four longer (3.55 Å) Gd–Sn bond lengths. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to four equivalent Gd and four equivalent Sn atoms. All Cu–Sn bond lengths are 2.58 Å. In the second Cu site, Cu is bonded in a 9-coordinate geometry to four equivalent Gd and five Sn atoms. There are one shorter (2.50 Å) and four longer (2.63 Å) Cu–Sn bond lengths. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Gd and four equivalent Cu atoms. In the second Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Gd and five Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(GaFe)6 by Materials Project

GdFe6Ga6 crystallizes in the orthorhombic Fmmm space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to twelve Fe and eight Ga atoms. There are eight shorter (3.12 Å) and four longer (3.30 Å) Gd–Fe bond lengths. There are four shorter (2.99 Å) and four longer (3.22 Å) Gd–Ga bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Gd, six Fe, and four equivalent Ga atoms to form distorted FeGd2Ga4Fe6 cuboctahedra that share corners with four equivalent GaGd2Ga6Fe4 cuboctahedra, corners with fourteen FeGd2Ga4Fe6 cuboctahedra, edges with four equivalent FeGd2Ga6Fe4 cuboctahedra, edges with four equivalent GaGd2Ga6Fe4 cuboctahedra, faces with four equivalent GaGd2Ga6Fe4 cuboctahedra, and faces with ten FeGd2Ga4Fe6 cuboctahedra. There are four shorter (2.45 Å) and two longer (2.54 Å) Fe–Fe bond lengths. All Fe–Ga bond lengths are 2.49 Å. In the second Fe site, Fe is bonded to two equivalent Gd, four Fe, and six Ga atoms to form distorted FeGd2Ga6Fe4 cuboctahedra that share corners with four equivalent GaGd2Ga6Fe4 cuboctahedra, corners with fourteen FeGd2Ga4Fe6 cuboctahedra, edges with two equivalent GaGd2Ga6Fe4 cuboctahedra, edges with five FeGd2Ga4Fe6 cuboctahedra, faces with four equivalent GaGd2Ga6Fe4 cuboctahedra, and faces with eleven FeGd2Ga4Fe6 cuboctahedra. There are one shorter (2.44 Å) and one longer (2.68 Å) Fe–Fe bond lengths. There are a spread of Fe–Ga bond distances ranging from 2.54–2.87 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded to two equivalent Gd, four equivalent Fe, and six Ga atoms to form GaGd2Ga6Fe4 cuboctahedra that share corners with six equivalent GaGd2Ga6Fe4 cuboctahedra, corners with twelve FeGd2Ga4Fe6 cuboctahedra, edges with eight FeGd2Ga4Fe6 cuboctahedra, faces with two equivalent GaGd2Ga6Fe4 cuboctahedra, and faces with twelve FeGd2Ga4Fe6 cuboctahedra. There are two shorter (2.54 Å) and four longer (2.76 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 12-coordinate geometry to one Gd, six Fe, and three Ga atoms. The Ga–Ga bond length is 2.54 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(Ga2Fe)4 by Materials Project

Gd(FeGa2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to eight equivalent Fe and twelve Ga atoms. All Gd–Fe bond lengths are 3.32 Å. There are four shorter (2.96 Å) and eight longer (3.17 Å) Gd–Ga bond lengths. Fe is bonded to two equivalent Gd, two equivalent Fe, and eight Ga atoms to form a mixture of distorted corner, edge, and face-sharing FeGd2Ga8Fe2 cuboctahedra. Both Fe–Fe bond lengths are 2.54 Å. There are four shorter (2.53 Å) and four longer (2.63 Å) Fe–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 12-coordinate geometry to two equivalent Gd, four equivalent Fe, and six Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.68–2.80 Å. In the second Ga site, Ga is bonded in a 10-coordinate geometry to one Gd, four equivalent Fe, and five Ga atoms. The Ga–Ga bond length is 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effect of chromium on corrosion resistance of Ni-Cr-Mo-Gd alloys in seawater

Neutron absorbing materials are being considered within commercial spent nuclear fuel disposal canisters to maintain nuclear subcriticality in storage. To select candidate alloys for the canisters, both neutron absorption and corrosion resistance should be considered. This work examines corrosion resistance of Ni-Cr-Mo-Gd alloys developed specifically for neutron absorption. The addition of Gd results in a secondary gadolinide phase (Ni 5 Gd) that significantly changes the corrosion properties. Testing was performed primarily in seawater at 30°C. Seawater was selected as the most prevalent terrestrial brine and is characterized by a high chloride concentration. Various electrochemical corrosion techniques were carried out to evaluate Ni-Cr-Mo-Gd alloys with different Cr compositions and investigate the role of Ni 5 Gd phase on corrosion behavior. C22 was included as a benchmark material, due to the similarity in composition and the significant corrosion data available. Here, test results showed a tendency to passivate over time which is attributed to dissolution of surface exposed Ni 5 Gd phase. Cross-sectional analysis indicated that dissolution could penetrate hundreds of micrometers deep under aggressive conditions. It was found that higher Cr variant (21.01%) showed much shallower impact, suggesting Cr prevented primary phase corrosion and thus reduced Ni 5 Gd phase dissolution. Acid pickling of the specimens showed much less dissolution for a higher Cr material and suggested some primary phase dissolution for the low Cr specimen. Acid pickled specimens showed positive shifts in the repassivation potential, suggesting increased surface passivation.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Modeling of fission gas diffusion and release for Gd 2 O 3 doped UO 2

Uranium dioxide (UO 2 ) is the primary nuclear fuel in light water reactors, and its excess neutronic reactivity can be controlled by adding burnable absorbers, such as Gd 2 O 3 . This burnable absorber has a large neutron absorption cross-section, lowering the high reactivity of the reactor's initial fuel load. However, there needs to be more understanding of how added Gd 2 O 3 influences the properties of UO 2 under irradiation. To understand the behavior of defects and fission gas in the UO 2 /Gd 2 O 3 system under irradiation, we use cluster dynamics modeling supported by density functional theory calculations. First, we calculate the formation energies of Gd point and cluster defects, and evaluate the temperature-dependent defect concentrations using the defect formation energies and entropies. We show that Gd is soluble in UO 2 , introducing a negative charge in the system. Using this information, we adapted the cluster dynamics code Centipede to model the influence of Gd on U self-diffusion and Xe diffusion in UO 2 with 10 wt% Gd 2 O 3 . Also, we analyzed the Xe diffusion as a function of Gd 2 O 3 concentration, showing that the Xe diffusivity is decreased, which means that the athermal diffusivity due to electronic stopping persists at higher temperatures. In conclusion, the decrease in Xe diffusion means that more Xe stays in the matrix, decreasing the Xe release, and lowering its influence of fission gas release on the thermomechanical properties of UO 2 .

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Structural characterization of highly alloyed (Al,Gd)N thin films

Highly alloyed (Al,Gd)N is of potential interest in a variety of applications, including neutron detection and in devices such as non-volatile memory. Gd has been shown to have very low equilibrium solubility in AlN at room temperature; however, non-equilibrium deposition techniques such as sputtering are able to deposit thin films, which incorporate large amounts of Gd. Here, we characterize a highly-alloyed (Al,Gd)N combinatorial thin film grown by RF sputtering on a GaN substrate, looking for any evidence of chemical or phase segregation or structural disorder in the films. Compositions with between 13% and 32% Gd (on a cation basis) were studied. No evidence was found for chemical or phase segregation in any studied composition. Higher degrees of Gd incorporation led to greater structural disorder in the film and a tendency toward amorphization; however, electron diffraction shows that the film does not become fully amorphous at any of the studied compositions, instead retaining textured local order even at 32% Gd. Electron energy loss spectra suggest that the material retains a locally wurtzite-like tetrahedral bonding environment at all studied compositions.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Decay spectroscopy of 160 Eu: Quasiparticle configurations of excited states and structure of K π = 4 + bandheads in 160 Gd

Background: Detailed spectroscopy of neutron-rich, heavy, deformed nuclei is of broad interest for nuclear astrophysics and nuclear structure. Nuclei in the r-process path and following freeze-out region impact the resulting r-process abundance distribution, and the structure of nuclei midshell in both proton and neutron number helps to understand the evolution of subshell gaps and large deformation in these nuclei. Purpose: We aim to improve the understanding of the nuclear structure of 160 Gd, specifically the K π = 4 + bands, as well as study the β decay of 160 Eu into 160 Gd. Methods: High-statistics decay spectroscopy of 160 Gd resulting from the β-decay of 160 Eu was collected using the GRIFFIN spectrometer at the TRIUMF-ISAC facility. Results: Two new excited states and ten new transitions were observed in 160 Gd. The β-decaying half-lives of the low- and high-spin isomers in 160 Eu were determined, and the low-spin state's half-life was measured to be t 1/2 = 26.0 (8) s, ≈ 16% shorter than previous measurements. Lifetimes of the two K π = 4 + bandheads in 160 Gd were measured for the first time, as well as γ – γ angular correlations and mixing ratios of intense transitions out of those bandheads. Conclusions: Lifetimes and mixing ratios suggest that the hexadecapole phonon model of the K π = 4 + bandheads in 160 Gd is preferred over a simple two-state strong mixing scenario, although further theoretical calculations are needed to fully understand these states. Additionally, the 1999.0-keV state in 160 Gd heavily populated in β decay is shown to have positive parity, which raises questions regarding the structure of the high-spin β-decaying state in 160 Eu.

150 ≤ A ≤ 189↗
DOE OSTI2022

Probability of Forming Gaps in the GD-1 Stream by Close Encounters of Globular Clusters

One of the most intriguing properties of the GD-1 stellar stream is the existence of three gaps. If these gaps were formed by close encounters with dark matter subhalos, the GD-1 stream opens an exciting window through which we can see the size, mass, and velocity distributions of the dark matter subhalos in the Milky Way. However, in order to use the GD-1 stream as a probe of the dark matter substructure, we need to disprove that these gaps are not due to the perturbations from baryonic components of the Milky Way. Here we ran a large number of test-particle simulations to investigate the probability that each of the known globular clusters (GCs) can form a GD-1-like gap, by using the kinematical data of the GD-1 stream and GCs from Gaia early data release 3 and by fully taking the observational uncertainty into account. We found that the probability that all of the three gaps were formed by GCs is as low as 1.7 × 10 -5 , and the expected number of gaps formed by GCs is only 0.057 in our fiducial model. Our result highly disfavors a scenario in which GCs form the gaps. Given that other baryonic perturbers (e.g., giant molecular clouds) are even less likely to form a gap in the retrograde-moving GD-1 stream, we conclude that at least one of the gaps in the GD-1 stream was formed by dark matter subhalos if the gaps were formed by flyby perturbations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Materials Data on Gd(SiPd)2 by Materials Project

Gd(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Si atoms. All Gd–Pd bond lengths are 3.26 Å. All Gd–Si bond lengths are 3.19 Å. Pd is bonded to four equivalent Gd and four equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing PdGd4Si4 tetrahedra. All Pd–Si bond lengths are 2.48 Å. Si is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Pd, and one Si atom. The Si–Si bond length is 2.34 Å.

36 MATERIALS SCIENCE↗