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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on UCu3Pd2 by Materials Project

UPd2Cu3 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. U is bonded in a 6-coordinate geometry to six equivalent Pd and ten Cu atoms. There are four shorter (2.96 Å) and two longer (2.99 Å) U–Pd bond lengths. There are a spread of U–Cu bond distances ranging from 3.01–3.22 Å. Pd is bonded to three equivalent U, two equivalent Pd, and seven Cu atoms to form a mixture of distorted face, edge, and corner-sharing PdU3Cu7Pd2 cuboctahedra. There are one shorter (2.68 Å) and one longer (2.70 Å) Pd–Pd bond lengths. There are a spread of Pd–Cu bond distances ranging from 2.55–3.06 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to three equivalent U, four equivalent Pd, and five Cu atoms. There are a spread of Cu–Cu bond distances ranging from 2.46–3.11 Å. In the second Cu site, Cu is bonded in a 12-coordinate geometry to four equivalent U, six equivalent Pd, and six equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2CdPd2 by Materials Project

Ho2Pd2Cd crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Ho is bonded in a 6-coordinate geometry to six equivalent Pd and four equivalent Cd atoms. There are two shorter (2.85 Å) and four longer (3.01 Å) Ho–Pd bond lengths. All Ho–Cd bond lengths are 3.40 Å. Pd is bonded in a 9-coordinate geometry to six equivalent Ho, one Pd, and two equivalent Cd atoms. The Pd–Pd bond length is 2.77 Å. Both Pd–Cd bond lengths are 3.04 Å. Cd is bonded to eight equivalent Ho and four equivalent Pd atoms to form a mixture of face and corner-sharing CdHo8Pd4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2CdPd2 by Materials Project

La2Pd2Cd crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. La is bonded in a 6-coordinate geometry to six equivalent Pd and four equivalent Cd atoms. There are two shorter (2.98 Å) and four longer (3.15 Å) La–Pd bond lengths. All La–Cd bond lengths are 3.53 Å. Pd is bonded in a 9-coordinate geometry to six equivalent La, one Pd, and two equivalent Cd atoms. The Pd–Pd bond length is 2.80 Å. Both Pd–Cd bond lengths are 3.12 Å. Cd is bonded to eight equivalent La and four equivalent Pd atoms to form a mixture of corner and face-sharing CdLa8Pd4 cuboctahedra.

36 MATERIALS SCIENCE↗
NASA NTRS2024

Pulsar-wind-nebula-powered Galactice center X-ray filament G0.13-0.11

We report the discovery of X-ray polarization from the X-ray-bright filament G0.13−0.11 in the Galactic center (GC) region. This filament features a bright, hard X-ray source that is most plausibly a pulsar wind nebula (PWN) and an extended and structured diffuse component. Combining the polarization signal from IXPE with the imaging/spectroscopic data fromChandra, we find that X-ray emission of G0.13−0.11 is highly polarized PD=57(±18)% in the 3−6 keV band, while the polarization angle is PA=21◦(±9◦). This high degree of polarization proves the synchrotron origin of the X-ray emission from G0.13−0.11. In turn, the measured polarization angle implies that the X-ray emission is polarized approximately perpendicular to a sequence of nonthermal radio filaments that may be part of the GC Radio Arc. The magnetic field on the order of 100μGappears to be preferentially ordered along the filaments. The above field strength is the fiducial value that makes our model self-consistent, while the other conclusions are largely model independent

magnetic fields↗
DOE OSTI2022

Experimental study of the partitioning of some platinum group elements (Pd and Ir) between orthopyroxene and silicate melt

Past experiments and observations on natural samples have largely focused on the roles of olivine and chromite in controlling the behaviour of the platinum-group elements (PGE) during melting and solidification, whereas other phases, such as pyroxene, have gone largely uncharacterized. Here, to address this, experiments have been done to measure the partitioning of Pd (with a subset of results for Ir), between orthopyroxene and silicate melt at 1340 °C, 0.1 MPa and log fO 2 of FMQ - 1 to FMQ + 6 (FMQ = Fayalite-Magnetite-Quartz). The X-ray Absorption Near-Edge Structure (XANES) was measured in a subset of experiment glasses. Glass concentrations of Pd (corrected to unit Pd activity) increase from ~6 to ~650 ug/g over the fO 2 range of experiments. The slope of the solubility-fO 2 relation is consistent with Pd 1+ as the dominant oxidation state, with evidence for Pd 0 and Pd 2+ at the lowest and highest experiment fO 2 , respectively. Consistent with this result, the XANES reveal spectral features similar to Pd 0 and Pd 2+ spectral reference materials (specRM) at the most reduced and oxidized synthesis conditions, respectively. Other lines of evidence require the presence of a third melt species, here interpreted to be Pd 1+ . Values of orthopyroxene/melt partition coefficients for Pd (D Pd Opx/melt ) are 0.0051 (+/-0.006) at log fO 2 < ΔFMQ + 3, increasing with fO 2 to a maximum of 0.013 at ~FMQ + 6. Sodium partition coefficients, expected to be similar to Pd, range from 0.0061 (+/-0.00061) at FMQ + 3, increase to 0.007–0.009 at higher fO 2 , but with no clear systematic trend. A value for D Ir Opx-melt of ~0.6 was measured at ~FMQ + 4, indicating significantly more compatible behaviour for Ir relative to Pd. Partitioning results are interpreted in the context of the Blundy-Wood elastic strain model in which the variation in partitioning is related to ionic radius mismatch to an optimal crystallographic site size. Based on the trend in ionic radius with oxidation state, the estimated ionic radius of Pd 1+ in octahedral coordination is similar to Na 1+ , and comparison to previous orthopyroxene-melt partitioning experiments suggests D Pd1+ opx/melt and DNaopx/melt should be nearly identical, consistent with the results of this study. The ionic radius of VI-fold Pd 2+ is close to the optimal M2 site size, so an increased proportion of this species with fO 2 accounts for the larger values of D Pd opx/melt at the highest fO 2 investigated. The much larger partition coefficient for Ir is consistent with the presence of Ir 2+ , whose estimated ionic radius is close to Fe 2+ and Mg 2+ , as well as predictions for the optimal M1 site size. With the assumption that D Pd opx/melt = D Na opx/melt , combined with a revised value for the Pd content of the primitive mantle, a melting model is presented that better reproduces the Pd concentration of high degree melts from sulfide-free mantle sources.

58 GEOSCIENCES↗
DOE OSTI2020

Materials Data on H3Pd4 by Materials Project

Pd4H3 is MAX Phase-derived structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three Pd4H3 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 3-coordinate geometry to three equivalent H atoms. All Pd–H bond lengths are 1.92 Å. In the second Pd site, Pd is bonded to six H atoms to form a mixture of edge and corner-sharing PdH6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (2.06 Å) and three longer (2.22 Å) Pd–H bond lengths. There are two inequivalent H sites. In the first H site, H is bonded to six Pd atoms to form a mixture of edge and corner-sharing HPd6 octahedra. The corner-sharing octahedral tilt angles are 6°. In the second H site, H is bonded to six equivalent Pd atoms to form a mixture of edge and corner-sharing HPd6 octahedra. The corner-sharing octahedral tilt angles are 6°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Computational modeling predicts the stability of both Pd + and Pd2 + ion-exchanged into H-CHA

Passive NO x adsorbers (PNA) using Pd/zeolites have emerged as a promising solution for the reduction of cold-start emissions from vehicle exhaust. However, the nature of the active sites and the mechanisms underlying NO x adsorption in Pd/zeolites remain a subject of ongoing investigation. In this study, we employ quantum chemical simulations to investigate the structure of Pd species in cation-exchange sites at isolated Al and Al pairs in the 6-ring and 8-ring of the CHA framework before the introduction of NO x . Our calculations show that the speciation of Pd in these exchange sites strongly depends on the precise Al arrangement within the framework, as well as the operating conditions. Ionically dispersed Pd is found to be the most favorable species over a wide range of oxidizing and reducing conditions. Small oligomers of PdO and metallic Pd do not appear to be competitive at either isolated Al or Al pairs. Notably, our calculations show that ion exchange sites other than next–next–nearest neighbor Al pairs in the 6-ring will be preferentially occupied by Pd + instead of Pd 2+ . The stability of Pd + in the zeolite environment is an interesting contrast with its rareness in molecular Pd compounds. Nonetheless, a detailed analysis of the electronic structure shows that predicted Pd oxidation states are consistent with chemical intuition for all complexes investigated in this study. We also discuss the potential ambiguity in Pd characterization provided by typical experimental techniques such as XANES, EXAFS and UV-Vis, and highlight the need for additional EPR spectroscopy studies to further elucidate the initial Pd speciation in zeolites for PNA applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

A Heterogeneous Palladium Catalyst for the Polymerization of Olefins Prepared by Halide Abstraction Using Surface R 3 Si + Species

Abstract The silylium‐like surface species [ i Pr 3 Si][(R F O) 3 Al−OSi≡)] activates (N^N)Pd(CH 3 )Cl (N^N=Ar−N=CMeMeC=N−Ar, Ar=2,6‐bis(diphenylmethyl)‐4‐methylbenzene) by chloride ion abstraction to form [(N^N)Pd−CH 3 ][(R F O) 3 Al−OSi≡)] ( 1 ). A combination of FTIR, solid‐state NMR spectroscopy, and reactions with CO or vinyl chloride establish that 1 shows similar reactivity patterns as (N^N)Pd(CH 3 )Cl activated with Na[B(Ar F ) 4 ]. Multinuclear 13 C{ 27 Al} RESPDOR and 1 H{ 19 F} S‐REDOR experiments are consistent with a weakly coordinated ion‐pair between (N^N)Pd−CH 3 + and [(R F O) 3 Al−OSi≡)]. 1 catalyzes the polymerization of ethylene with similar activities as [(N^N)Pd−CH 3 ] + in solution and incorporates up to 0.4 % methyl acrylate in copolymerization reactions. 1 produces polymers with significantly higher molecular weight than the solution catalyst, and generates the highest molecular weight polymers currently reported in copolymerization reactions of ethylene and methylacrylate.

Gao, Jiaxin↗
DOE OSTI2020

Materials Data on Yb2Sn5Pd3 by Materials Project

Yb2Pd3Sn5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Yb sites. In the first Yb site, Yb is bonded in a 1-coordinate geometry to five Pd and eight Sn atoms. There are a spread of Yb–Pd bond distances ranging from 2.92–3.38 Å. There are a spread of Yb–Sn bond distances ranging from 3.20–3.44 Å. In the second Yb site, Yb is bonded in a 8-coordinate geometry to two equivalent Pd and six Sn atoms. Both Yb–Pd bond lengths are 3.29 Å. There are four shorter (3.24 Å) and two longer (3.27 Å) Yb–Sn bond lengths. There are three inequivalent Pd sites. In the first Pd site, Pd is bonded in a 9-coordinate geometry to three Yb and six Sn atoms. There are a spread of Pd–Sn bond distances ranging from 2.74–2.94 Å. In the second Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent Yb and five Sn atoms. There are a spread of Pd–Sn bond distances ranging from 2.69–2.83 Å. In the third Pd site, Pd is bonded in a 7-coordinate geometry to seven Sn atoms. There are a spread of Pd–Sn bond distances ranging from 2.76–2.91 Å. There are five inequivalent Sn sites. In the first Sn site, Sn is bonded in a 6-coordinate geometry to two equivalent Yb and four Pd atoms. In the second Sn site, Sn is bonded in a 5-coordinate geometry to two equivalent Yb, three equivalent Pd, and one Sn atom. The Sn–Sn bond length is 3.10 Å. In the third Sn site, Sn is bonded in a 12-coordinate geometry to four equivalent Yb and four Pd atoms. In the fourth Sn site, Sn is bonded in a 4-coordinate geometry to two equivalent Yb and four Pd atoms. In the fifth Sn site, Sn is bonded in a 3-coordinate geometry to four Yb, three Pd, and one Sn atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Revealing the Influence of Diverse Secondary Metal Cations on Redox-Active Palladium Complexes

Incorporation of redox-inactive metals into redox-active complexes and catalysts attracts attention for engendering new reactivity modes, but this strategy has not been extensively investigated beyond the first-row of the transition metals. In this report the isolation and characterization of the first series of heterobimetallic complexes of palladium with mono-, di-, and tri-valent redox-inactive metal ions are reported. A Reinhoudt-type heteroditopic ligand with a salen-derived [N 2 ,O 2 ] binding site for Pd and a crown-ether-derived [O 6 ] site has been used to prepare isolable adducts of the Lewis acidic redox-inactive metal ions (M n+ ). Comprehensive data from single-crystal X-ray diffraction analysis reveal distinctive trends in the structural properties of the heterobimetallic species, including an uncommon dependence of the Pd … M distance on Lewis acidity. The reorganization energy associated with reduction of the heterobimetallic species is strongly modulated by Lewis acidity, with the slowest heterogeneous electron transfer kinetics associated with the strongest incorporated Lewis acids. This hitherto unexplored reorganization energy penalty for electron transfer contrasts with prior thermodynamic studies, revealing that kinetic parameters should be considered in studies of reactivity involving heterobimetallic species.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Mn5(Bi2Pd)2 by Materials Project

Mn5Pd2Bi4 crystallizes in the cubic F-43m space group. The structure is three-dimensional. there are two inequivalent Mn sites. In the first Mn site, Mn is bonded in a 10-coordinate geometry to two equivalent Mn, two equivalent Pd, and six Bi atoms. Both Mn–Mn bond lengths are 2.92 Å. Both Mn–Pd bond lengths are 2.74 Å. There are a spread of Mn–Bi bond distances ranging from 3.09–3.13 Å. In the second Mn site, Mn is bonded in a 6-coordinate geometry to three equivalent Mn, three equivalent Pd, and four Bi atoms. All Mn–Pd bond lengths are 2.69 Å. There are three shorter (2.93 Å) and one longer (3.26 Å) Mn–Bi bond lengths. Pd is bonded in a 10-coordinate geometry to six Mn and four Bi atoms. There are one shorter (2.83 Å) and three longer (2.97 Å) Pd–Bi bond lengths. There are three inequivalent Bi sites. In the first Bi site, Bi is bonded in a 8-coordinate geometry to six Mn and two equivalent Pd atoms. In the second Bi site, Bi is bonded in a 10-coordinate geometry to ten Mn atoms. In the third Bi site, Bi is bonded in a distorted q6 geometry to six equivalent Mn and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf6Ga16Pd7 by Materials Project

Hf6Pd7Ga16 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Hf is bonded in a 4-coordinate geometry to four equivalent Pd and four equivalent Ga atoms. All Hf–Pd bond lengths are 3.22 Å. All Hf–Ga bond lengths are 2.83 Å. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded to four equivalent Hf and eight Ga atoms to form a mixture of distorted face and corner-sharing PdHf4Ga8 cuboctahedra. There are four shorter (2.55 Å) and four longer (2.72 Å) Pd–Ga bond lengths. In the second Pd site, Pd is bonded in a body-centered cubic geometry to eight equivalent Ga atoms. All Pd–Ga bond lengths are 2.63 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 6-coordinate geometry to three equivalent Hf and three equivalent Pd atoms. In the second Ga site, Ga is bonded in a 4-coordinate geometry to four Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr6Ga16Pd7 by Materials Project

Zr6Pd7Ga16 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Zr is bonded in a 4-coordinate geometry to four equivalent Pd and eight Ga atoms. All Zr–Pd bond lengths are 3.22 Å. There are four shorter (2.87 Å) and four longer (3.18 Å) Zr–Ga bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded to four equivalent Zr and eight Ga atoms to form a mixture of distorted corner and face-sharing PdZr4Ga8 cuboctahedra. There are four shorter (2.56 Å) and four longer (2.74 Å) Pd–Ga bond lengths. In the second Pd site, Pd is bonded in a body-centered cubic geometry to eight equivalent Ga atoms. All Pd–Ga bond lengths are 2.64 Å. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 6-coordinate geometry to three equivalent Zr and three equivalent Pd atoms. In the second Ga site, Ga is bonded in a 4-coordinate geometry to three equivalent Zr and four Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Peculiarities of the phase transformation dynamics in bulk FeRh based alloys from magnetic and structural measurements

We analyze coexistence of antiferromagnetic and ferromagnetic phases in bulk iron-rhodium and its alloys with palladium, Fe 50,4 Rh 49,6 , Fe 49,7 Rh 47,4 Pd 2,9 and Fe 48,3 Rh 46,8 Pd 4,9 , using neutron diffraction, magnetization and scanning Hall probe imaging. Temperature dependencies of the lattice parameters, AFM and FM phase weight fractions, and Fe magnetic moment values were obtained on cooling and heating across the AFM-FM transition. Substantial thermomagnetic hysteresis for the phases’ weight fractions and a relatively narrow one for the unit cell volume has been observed on cooling-heating. Furthermore, a clear dependence of hysteretic behavior on Pd concentration has been traced. Additional direct magnetic measurements of the spatial distribution of the phase transition are acquired using scanning Hall probe microscopy, which reveals the length scale of the phase coexistence and the spatial progression of the transition in the presence of external magnetic field. Also, the magnetic phase diagram has been constructed for a series of Pd-doped FeRh alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ligand-coordination effects on the selective hydrogenation of acetylene in single-site Pd-ligand supported catalysts

The selective hydrogenation of acetylene to ethylene is a critical step in the synthesis of polyethylenes. Achieving high conversion to ethylene without over-hydrogenation to ethane is a challenge that requires control of the transition metal site, which we achieve through a ligand-coordinated supported catalyst (LCSC) strategy. Using Pd catalysts coordinated to 1,10-phenanthroline-5,6-dione (PDO) ligands on CeO2 supports, we have discovered that the reaction selectivity depends strongly on the ligand:metal ratio with higher selectivity when more ligand is present in the catalyst. Catalyst structure was examined by extended X-ray absorption fine structure spectroscopy, transmission electron microscopy, and CO adsorption, which indicate single-atom character of the Pd. The ligand:metal ratio is determined by Xray photoelectron spectroscopy measurements and correlated with hydrogenation reactions under steady-state flow conditions to examine trends in hydrogenation activity and selectivity. Those trends can be better understood by density functional theory calculations that indicate hydrogen binding on the ligand to guide reaction selectivity toward the desired ethylene hydrogenation product. Here these results demonstrate the importance of considering the dynamic character of LCSCs and inform the design of future single-site heterogeneous catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

A Heterogeneous Palladium Catalyst for the Polymerization of Olefins Prepared by Halide Abstraction Using Surface R 3 Si + Species

The silylium-like surface species [ i Pr 3 Si][(R F O) 3 Al-OSi≡)] activates (N^N)Pd(CH 3 )Cl (N^N=Ar-N=CMeMeC=N-Ar, Ar=2,6-bis(diphenylmethyl)-4-methylbenzene) by chloride ion abstraction to form [(N^N)Pd-CH 3 ][(R F O) 3 Al-OSi≡)] ( 1 ). A combination of FTIR, solid-state NMR spectroscopy, and reactions with CO or vinyl chloride establish that 1 shows similar reactivity patterns as (N^N)Pd(CH 3 )Cl activated with Na[B(Ar F ) 4 ]. Multinuclear 13 C{ 27 Al} RESPDOR and 1 H{ 19 F} S-REDOR experiments are consistent with a weakly coordinated ion-pair between (N^N)Pd-CH 3 + and [(R F O) 3 Al-OSi≡)]. 1 catalyzes the polymerization of ethylene with similar activities as [(N^N)Pd-CH 3 ] + in solution and incorporates up to 0.4% methyl acrylate in copolymerization reactions. 1 produces polymers with significantly higher molecular weight than the solution catalyst, and generates the highest molecular weight polymers currently reported in copolymerization reactions of ethylene and methylacrylate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Sr(SiPd)6 by Materials Project

Sr(PdSi)6 crystallizes in the orthorhombic Ibam space group. The structure is three-dimensional and consists of four strontium molecules and one PdSi framework. In the PdSi framework, there are two inequivalent Pd+2.33+ sites. In the first Pd+2.33+ site, Pd+2.33+ is bonded in a 5-coordinate geometry to five Si+2.67- atoms. There are a spread of Pd–Si bond distances ranging from 2.45–2.62 Å. In the second Pd+2.33+ site, Pd+2.33+ is bonded in a 7-coordinate geometry to seven Si+2.67- atoms. There are a spread of Pd–Si bond distances ranging from 2.44–2.98 Å. There are two inequivalent Si+2.67- sites. In the first Si+2.67- site, Si+2.67- is bonded in a 5-coordinate geometry to six Pd+2.33+ atoms. In the second Si+2.67- site, Si+2.67- is bonded in a 4-coordinate geometry to five Pd+2.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SbPd by Materials Project

PdSb is Tungsten Carbide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Pd2+ is bonded to six equivalent Sb2- atoms to form a mixture of face, edge, and corner-sharing PdSb6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Pd–Sb bond lengths are 2.78 Å. Sb2- is bonded in a 6-coordinate geometry to six equivalent Pd2+ atoms.

36 MATERIALS SCIENCE↗