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NASA NTRS1984

Structural characterizaiton and gas reactions of small metal particles by high-resolution, in-situ TEM and TED

The existing in-situ transmission electron microscopy (TEM) facility was improved by adding a separately pumped mini-specimen chamber. The chamber contains wire-evaporation sources for three metals and a specimen heater for moderate substrate temperatures. A sample introduction device was constructed, installed, and tested, facilitating rapid introduction of a specimen into the mini-chamber while maintaining the background pressure in that chamber in the 10(-9) millibar range. Small particles and clusters of Pd, grown by deposition from the vapor phase in an in-situ TEM facility on amorphous and crystalline support films of alumina and on ultra-thin carbon films, were analyzed by conventional high-resolution TEM and image analysis in terms of detectability, number density, and size distribution. The smallest particles that could be detected and counted contained no more than 6 atoms; size determinations could be made for particles 1 nm in diameter. The influence of various oxygen plasma treatments, annealing treatments, and of increasing the substrate temperature during deposition was investigated. The TEM technique was employed to demonstrate that under otherwise identica l conditions the lattice parameter of Pd particles in the 1 to 2 nm size range and supported in random orientation on ex-situ prepared mica films is expanded by some 3% when compared to 5 nm size particles. It is believed that this expansion is neither a small-particle diffraction effect nor due to pseudomorphism, but that it is due to a annealing-induced transformation of the small as-deposited particles with predominantly composite crystal structures into larger particles with true f.c.c. structure and thus inherently smaller lattice parameter.

Source record↗
DOE OSTI2020

Materials Data on Li15Bi4(PdO10)2 by Materials Project

Li15Bi4(PdO10)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are fifteen inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.01–2.73 Å. In the second Li1+ site, Li1+ is bonded to five O2- atoms to form LiO5 trigonal bipyramids that share a cornercorner with one LiO6 octahedra, corners with two BiO6 octahedra, corners with three LiO5 trigonal bipyramids, edges with two BiO6 octahedra, and edges with four LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 9–11°. There are a spread of Li–O bond distances ranging from 2.09–2.24 Å. In the third Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share a cornercorner with one BiO6 octahedra, corners with three LiO6 octahedra, a cornercorner with one LiO5 trigonal bipyramid, edges with three BiO6 octahedra, edges with five LiO6 octahedra, and an edgeedge with one LiO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 6–12°. There are a spread of Li–O bond distances ranging from 1.99–2.42 Å. In the fourth Li1+ site, Li1+ is bonded to five O2- atoms to form LiO5 trigonal bipyramids that share a cornercorner with one LiO6 octahedra, corners with four LiO5 trigonal bipyramids, an edgeedge with one LiO6 octahedra, edges with three BiO6 octahedra, and edges with two LiO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 13°. There are a spread of Li–O bond distances ranging from 2.00–2.41 Å. In the fifth Li1+ site, Li1+ is bonded to six O2- atoms to form distorted LiO6 octahedra that share a cornercorner with one BiO6 octahedra, corners with three LiO6 octahedra, a cornercorner with one LiO5 trigonal bipyramid, edges with three BiO6 octahedra, edges with five LiO6 octahedra, and edges with two LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 5–13°. There are a spread of Li–O bond distances ranging from 2.04–2.64 Å. In the sixth Li1+ site, Li1+ is bonded to five O2- atoms to form LiO5 trigonal bipyramids that share a cornercorner with one LiO6 octahedra, corners with two BiO6 octahedra, corners with four LiO5 trigonal bipyramids, an edgeedge with one LiO6 octahedra, edges with two BiO6 octahedra, and edges with three LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 1–17°. There are a spread of Li–O bond distances ranging from 2.03–2.26 Å. In the seventh Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share a cornercorner with one BiO6 octahedra, corners with two equivalent LiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with three BiO6 octahedra, edges with six LiO6 octahedra, and an edgeedge with one LiO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 5–11°. There are a spread of Li–O bond distances ranging from 2.13–2.44 Å. In the eighth Li1+ site, Li1+ is bonded to five O2- atoms to form distorted LiO5 trigonal bipyramids that share corners with two LiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with three LiO6 octahedra, edges with three BiO6 octahedra, and edges with two LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 12–15°. There are a spread of Li–O bond distances ranging from 2.00–2.47 Å. In the ninth Li1+ site, Li1+ is bonded to five O2- atoms to form LiO5 trigonal bipyramids that share a cornercorner with one LiO6 octahedra, corners with four LiO5 trigonal bipyramids, an edgeedge with one LiO6 octahedra, edges with three BiO6 octahedra, and edges with two LiO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°. There are a spread of Li–O bond distances ranging from 2.01–2.35 Å. In the tenth Li1+ site, Li1+ is bonded to six O2- atoms to form distorted LiO6 octahedra that share a cornercorner with one BiO6 octahedra, corners with three LiO6 octahedra, edges with three BiO6 octahedra, edges with five LiO6 octahedra, and edges with two LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 6–13°. There are a spread of Li–O bond distances ranging from 2.04–2.70 Å. In the eleventh Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share a cornercorner with one BiO6 octahedra, corners with three LiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with three BiO6 octahedra, edges with five LiO6 octahedra, and an edgeedge with one LiO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 6–12°. There are a spread of Li–O bond distances ranging from 2.05–2.52 Å. In the twelfth Li1+ site, Li1+ is bonded to five O2- atoms to form LiO5 trigonal bipyramids that share a cornercorner with one LiO6 octahedra, corners with two BiO6 octahedra, corners with three LiO5 trigonal bipyramids, an edgeedge with one LiO6 octahedra, edges with two BiO6 octahedra, and edges with three LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 3–20°. There are a spread of Li–O bond distances ranging from 2.00–2.27 Å. In the thirteenth Li1+ site, Li1+ is bonded to five O2- atoms to form LiO5 trigonal bipyramids that share a cornercorner with one LiO6 octahedra, corners with two BiO6 octahedra, corners with four LiO5 trigonal bipyramids, edges with two BiO6 octahedra, and edges with four LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 5–10°. There are a spread of Li–O bond distances ranging from 2.07–2.19 Å. In the fourteenth Li1+ site, Li1+ is bonded to six O2- atoms to form distorted LiO6 octahedra that share a cornercorner with one BiO6 octahedra, corners with two equivalent LiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with three BiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 4–11°. There are a spread of Li–O bond distances ranging from 2.05–2.59 Å. In the fifteenth Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 1.99–2.68 Å. There are two inequivalent Pd4+ sites. In the first Pd4+ site, Pd4+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Pd–O bond distances ranging from 1.96–2.06 Å. In the second Pd4+ site, Pd4+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are a spread of Pd–O bond distances ranging from 1.96–2.07 Å. There are four inequivalent Bi+4.25+ sites. In the first Bi+4.25+ site, Bi+4.25+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with two LiO6 octahedra, corners with two equivalent BiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with three LiO6 octahedra, and edges with five LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 6–15°. There are a spread of Bi–O bond distances ranging from 2.06–2.22 Å. In the second Bi+4.25+ site, Bi+4.25+ is bonded to six O2- atoms to form BiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with two equivalent BiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with six LiO6 octahedra, and edges with three LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 4–17°. There are a spread of Bi–O bond distances ranging from 2.06–2.24 Å. In the third Bi+4.25+ site, Bi+4.25+ is bonded to six O2- atoms to form BiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with two equivalent BiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with six LiO6 octahedra, and edges with four LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 5–17°. There are a spread of Bi–O bond distances ranging from 2.08–2.22 Å. In the fourth Bi+4.25+ site, Bi+4.25+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with two LiO6 octahedra, corners with two equivalent BiO6 octahedra, corners with two LiO5 trigonal bipyramids, edges with three LiO6 octahedra, and edges with five LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 5–15°. There are a spread of Bi–O bond distances ranging from 2.06–2.22 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded to three Li1+, one Pd4+, and one Bi+4.25+ atom to form OLi3BiPd trigonal bipyramids that share corners with five OLi4BiPd octahedra, a cornercorner with one OLi4Bi square pyramid, edges with four OLi4BiPd octahedra, and an edgeedge with one OLi3Bi2 square pyramid. The corner-sharing octahedra tilt angles range from 2–27°. In the second O2- site, O2- is bonded to four Li1+, one Pd4+, and one Bi+4.25+ atom to form distorted OLi4BiPd octahedra that share corners with four OLi4BiPd octahedra, edges with nine OLi4Bi2 octahedra, and an edgeedge with one OLi3BiPd trigonal bipyramid. The corner-sharing octahedra tilt angles range from 3–22°. In the third O2- site, O2- is bonded to five Li1+ and one Bi+4.25+ atom to form OLi5Bi octahedra that share corners with five OLi4Bi2 octahedra, edges with eleven OLi4Bi2 octahedra, and an edgeedge with one OLi4Bi square pyramid. The corner-sharing octahedra tilt angles range from 3–19°. In the fourth O2- site, O2- is bonded to five Li1+ and one Bi+4.25+ atom to form OLi5Bi octahedra that share corners with five OLi5Bi octahedra, a cornercorner with one OLi3BiPd trigonal bipyramid, edges with eight OLi5Bi octahedra, and edges with three OLi3Bi2 square pyramids. The corner-sharing octahedra tilt angles range from 3–14°. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to three Li1+, one Pd4+, and one Bi+4.25+ atom. In the sixth O2- site, O2- is bonded to five Li1+ and one Bi+4.25+ atom to form distorted OLi5Bi octahedra that share corners with four OLi4Bi2 octahedra, a cornercorner with one OLi4Bi square pyramid, edges with ten OLi4BiPd octahedra, and edges with two OLi3Bi2 square pyramids. The corner-sharing octahedra tilt angles range from 10–19°. In the seventh O2- site, O2- is bonded to four Li1+ and two Bi+4.25+ atoms to form OLi4Bi2 octahedra that share corners with four OLi4BiPd octahedra, corners with two equivalent OLi3Bi2 square pyramids, edges with six OLi4BiPd octahedra, an edgeedge with one OLi4Bi square pyramid, and an edgeedge with one OLi3BiPd trigonal bipyramid. The corner-sharing octahedra tilt angles range from 9–14°. In the eighth O2- site, O2- is bonded to four Li1+, one Pd4+, and one Bi+4.25+ atom to form OLi4BiPd octahedra that share corners with five OLi4Bi2 octahedra, a cornercorner with one OLi3BiPd trigonal bipyramid, edges with seven OLi4BiPd octahedra, and an edgeedge with one OLi3BiPd trigonal bipyramid. The corner-sharing octahedra tilt angles range from 8–20°. In the ninth O2- site, O2- is bonded in a 5-coordinate geometry to three Li1+, one Pd4+, and one Bi+4.25+ atom. In the tenth O2- site, O2- is bonded to five Li1+ and one Bi+4.25+ atom to form OLi5Bi octahedra that share corners with five OLi5Bi octahedra and edges with twelve OLi4BiPd octahedra. The corner-sharing octahedra tilt angles range from 7–20°. In the eleventh O2- site, O2- is bonded to five Li1+ and one Bi+4.25+ atom to form OLi5Bi octahedra that share corners with two OLi4Bi2 octahedra, corners with two equivalent OLi4Bi square pyramids, edges with nine OLi4BiPd octahedra, and an edgeedge with one OLi3Bi2 square pyramid. The corner-sharing octahedra tilt angles range from 3–6°. In the twelfth O2- site, O2- is bonded to four Li1+, one Pd4+, and one Bi+4.25+ atom to form distorted OLi4BiPd octahedra that share corners with four OLi5Bi octahedra and edges with ten OLi4BiPd octahedra. The corner-sharing octahedra tilt angles range from 3–22°. In the thirteenth O2- site, O2- is bonded to four Li1+, one Pd4+, and one Bi+4.25+ atom to form OLi4BiPd octahedra that share corners with four OLi4Bi2 octahedra, corners wi

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KEuPdO3 by Materials Project

KEuPdO3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.66–3.08 Å. Eu3+ is bonded to seven O2- atoms to form distorted edge-sharing EuO7 hexagonal pyramids. There are a spread of Eu–O bond distances ranging from 2.30–2.59 Å. Pd2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are a spread of Pd–O bond distances ranging from 2.01–2.09 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent K1+, three equivalent Eu3+, and one Pd2+ atom to form distorted OK2Eu3Pd octahedra that share corners with five equivalent OK3Eu2Pd octahedra and edges with eight OK2Eu3Pd octahedra. The corner-sharing octahedra tilt angles range from 6–8°. In the second O2- site, O2- is bonded to three equivalent K1+, two equivalent Eu3+, and one Pd2+ atom to form a mixture of distorted edge and corner-sharing OK3Eu2Pd octahedra. The corner-sharing octahedra tilt angles range from 6–8°. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent K1+, two equivalent Eu3+, and two equivalent Pd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Hydrothermally stable Pd/SiO 2 @Zr Core@Shell catalysts for diesel oxidation applications

Hydrothermally stable diesel oxidation catalysts (DOCs) with improved low-temperature activity are desired for the abatement of emissions from diesel vehicles. Herein, novel palladium(Pd)/SiO 2 (core)@Zr(shell) structured DOCs were developed. SiO 2 was completely covered by an 8.4 nm thickness Zr-based shell using a hard template method. The SiO 2 @Zr support was decorated by Pd and evaluated under a simulated diesel exhaust stream. Degreened 1 wt% Pd/SiO 2 @Zr achieved 90% CO and total hydrocarbon conversion at 178 and 372 °C, respectively (feed: 6% CO 2 , 12% O 2 , 6% H 2 O, 400 ppm H 2 , 2000 ppm CO, 100 ppm NO, 1667 ppm C 2 H 4 , 1000 ppm C 3 H 6 , 333 ppm C 3 H 8 ; HCs in C 1 basis and GHSV = 113,000 h –1 ). After hydrothermal aging, only a minor deactivation was observed, while the surface area of 1 wt% Pd/SiO 2 @Zr was as high as 104 m 2 /g. The hydrothermal stability of 1 wt% Pd/SiO 2 @Zr was attributed to the poor crystallinity of SiO 2 @Zr, possibly due to the formation of Si-O-Zr bonds. Lastly, this work highlights the promising potential of utilizing durable Pd/SiO 2 @Zr catalysts for diesel oxidation applications.

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

Materials Data on Ba4PdO6 by Materials Project

Ba4PdO6 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. There are a spread of Ba–O bond distances ranging from 2.76–2.94 Å. In the second Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Ba–O bond lengths are 2.65 Å. Pd4+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Pd–O bond lengths are 2.12 Å. O2- is bonded to five Ba2+ and one Pd4+ atom to form a mixture of distorted face, edge, and corner-sharing OBa5Pd octahedra. The corner-sharing octahedra tilt angles range from 0–61°.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Tuning spin–orbit coupling in (6,5) single-walled carbon nanotube doped with sp 3 defects

Single-walled carbon nanotubes (SWCNTs) containing sp 3 defects are a promising class of optoelectronic materials with bright photoluminescence and demonstrated single-photon emission. Using density functional theory simulations, complemented by measurements, we investigate the electronic structure of a series of quantum defects attached to (6,5) SWCNT with the goal of tuning the spin–orbit coupling by introduction of a heavy atom in the defect structure. We characterize the ground state electronic and spin properties of four synthesized and three potential defects on the tube and find that all of the synthesized defects considered introduce a localized midgap defect-centered state containing a single electron, ≈0.2–0.3 eV above the valence band. The spin density is located at the sp 3 defect site with negligible spin–orbit coupling even with the presence of a Pd atom. Three additional functional groups were tested via computation to increase spin localization near the metal, thereby increasing spin–orbit coupling. We predict that only the chlorodiphosphanepalladium(II)– [Cl(PH 3 ) 2 Pd(II)–] defect results in increased spin–orbit splitting of the defect state and the conduction band associated with the pristine-like SWCNT, a measure of the spin–orbit coupling of excited state transitions. This study suggests that for unpassivated sp 3 defects in (6,5) SWCNT, forming a direct bond between a heavy atom and the sp 3 carbon allows for tuning of spin–orbit coupling.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Materials Data on La6P17Pd6 by Materials Project

La6Pd6P17 crystallizes in the cubic I-43m space group. The structure is three-dimensional. La+2.50+ is bonded in a 7-coordinate geometry to nine P+1.59- atoms. There are a spread of La–P bond distances ranging from 3.00–3.45 Å. Pd2+ is bonded in a square co-planar geometry to four equivalent P+1.59- atoms. All Pd–P bond lengths are 2.36 Å. There are three inequivalent P+1.59- sites. In the first P+1.59- site, P+1.59- is bonded in a 5-coordinate geometry to three equivalent La+2.50+, two equivalent Pd2+, and one P+1.59- atom. The P–P bond length is 2.22 Å. In the second P+1.59- site, P+1.59- is bonded in a 6-coordinate geometry to three equivalent La+2.50+ and three equivalent P+1.59- atoms. In the third P+1.59- site, P+1.59- is bonded in an octahedral geometry to six equivalent La+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Evaluation of different getter substrates using two-dimensional gas chromatography with time of flight mass spectrometry

We report while understanding hydrogen uptake by organic based getters such as 1,4-bis(phenylethynyl)benzene (DEB) combined with a palladium(0)bis(dibenzylideneacetone) (Pd(dba) 2 ) catalyst is essential, another crucial element to understand is the decomposition of the DEB, Pd(dba) 2 , and/or substrate material. The breakdown of these materials may create unwanted volatiles, which may interact with and lead to deterioration of sensitive materials. Moreover, it is critical to understand if different substrates cause the getter and/or catalyst to degrade in different manners. Utilizing comprehensive two-dimensional gas chromatography (GC×GC) with time-of-flight mass spectrometry (TOFMS), the presence of volatiles located in the headspace of various DEB/Pd(dba) 2 getter substrates is examined. These samples include a getter infused silicone foam, a hydrogenated getter infused silicone foam, an activated carbon getter pellet, and a hydrogenated activated carbon getter pellet. Application of Fisher ratio (F-ratio) analyses lead to the identification of several compounds that are generated or consumed through the hydrogenation process. These include benzene derivatives such as bibenzyl, benzaldehyde, and vinyl benzoate in the activated carbon pellets and 1,5-diphenyl-3-pentanone, toluene, styrene, and 1–1'(2-pentene 1,5-diyl)bis benzene in the silicone foams, and alkane/alkene derivatives such undecane, 4-tridecene, and decane in the activated carbon pellets and 2,6-dimethyl undecane in the silicone foams. Further comparison of the different hydrogenated getter substrates (e.g. activated carbon pellet and silicone foam) indicates that the different substrates alter the decomposition products created from the degradation of the DEB and Pd(dba) 2 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Exploring dimethyl sulfide (DMS) oxidation and implications for global aerosol radiative forcing

Abstract. Aerosol indirect radiative forcing (IRF), which characterizes how aerosols alter cloud formation and properties, is very sensitive to the preindustrial (PI) aerosol burden. Dimethyl sulfide (DMS), emitted from the ocean, is a dominant natural precursor of non-sea-salt sulfate in the PI and pristine present-day (PD) atmospheres. Here we revisit the atmospheric oxidation chemistry of DMS, particularly under pristine conditions, and its impact on aerosol IRF. Based on previous laboratory studies, we expand the simplified DMS oxidation scheme used in the Community Atmospheric Model version 6 with chemistry (CAM6-chem) to capture the OH-addition pathway and the H-abstraction pathway and the associated isomerization branch. These additional oxidation channels of DMS produce several stable intermediate compounds, e.g., methanesulfonic acid (MSA) and hydroperoxymethyl thioformate (HPMTF), delay the formation of sulfate, and, hence, alter the spatial distribution of sulfate aerosol and radiative impacts. The expanded scheme improves the agreement between modeled and observed concentrations of DMS, MSA, HPMTF, and sulfate over most marine regions, based on the NASA Atmospheric Tomography (ATom), the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA), and the Variability of the American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) measurements. We find that the global HPMTF burden and the burden of sulfate produced from DMS oxidation are relatively insensitive to the assumed isomerization rate, but the burden of HPMTF is very sensitive to a potential additional cloud loss. We find that global sulfate burden under PI and PD emissions increase to 412 Gg S (+29 %) and 582 Gg S (+8.8 %), respectively, compared to the standard simplified DMS oxidation scheme. The resulting annual mean global PD direct radiative effect of DMS-derived sulfate alone is −0.11 W m−2. The enhanced PI sulfate produced via the gas-phase chemistry updates alone dampens the aerosol IRF as anticipated (−2.2 W m−2 in standard versus −1.7 W m−2, with updated gas-phase chemistry). However, high clouds in the tropics and low clouds in the Southern Ocean appear particularly sensitive to the additional aqueous-phase pathways, counteracting this change (−2.3 W m−2). This study confirms the sensitivity of aerosol IRF to the PI aerosol loading and the need to better understand the processes controlling aerosol formation in the PI atmosphere and the cloud response to these changes.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2013

Late Chondritic Additions and Planet and Planetesimal Growth: Evaluation of Physical and Chemical Mechanisms

Studies of terrestrial peridotite and martian and achondritic meteorites have led to the conclusion that addition of chondritic material to growing planets or planetesimals, after core formation, occurred on Earth, Mars, asteroid 4 Vesta, and the parent body of the angritic meteorites [1-4]. One study even proposed that this was a common process in the final stages of growth [5]. These conclusions are based almost entirely on the highly siderophile elements (HSE; Re, Au, Pt, Pd, Rh, Ru, Ir, Os). The HSE are a group of eight elements that have been used to argue for late accretion of chondritic material to the Earth after core formation was complete (e.g., [6]). This idea was originally proposed because the D(metal/silicate) values for the HSE are so high, yet their concentration in the mantle is too high to be consistent with such high Ds. The HSE also are present in chondritic relative abundances and hence require similar Ds if this is the result of core-mantle equilibration. Since the work of [6] there has been a realization that core formation at high PT conditions can explain the abundances of many siderophile elements in the mantle (e.g., [7]), but such detailed high PT partitioning data are lacking for many of the HSE to evaluate whether such ideas are viable for all four bodies. Consideration of other chemical parameters reveals larger problems that are difficult to overcome, but must be addressed in any scenario which calls on the addition of chondritic material to a reduced mantle. Yet these problems are rarely discussed or emphasized, making the late chondritic (or late veneer) addition hypothesis suspect.

Righter, Kevin↗
DOE OSTI2023

Lifetime measurement of excited states in 116 Xe

Lifetimes of excited states in 116 Xe were measured using the recoil-distance Doppler-shift technique. Excited 116 Xe nuclei were populated in the fusion-evaporation reaction 102 Pd( 16 O,2n) 116 Xe. Lifetimes of the $2^{+}_{1}$ and $4^{+}_{1}$ states were evaluated using the differential decay-curve method with $\gamma$-$\gamma$-coincidence data as well as lifetimes of the $6^{+}_{1}$ and $7^{-}_{1}$ states using simulations of spectra considering Doppler-shift attenuation effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1995

Quaternary borocarbides: New class of intermetallic superconductors

Our recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. Our investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In our multiphase ThNi2B2C we observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

Nagarajan, R.↗
DOE OSTI2020

Materials Data on Na2Pd(SeO4)2 by Materials Project

Na2Pd(SeO4)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.39–2.83 Å. Pd4+ is bonded in a square co-planar geometry to four O2- atoms. All Pd–O bond lengths are 2.04 Å. Se5+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Se–O bond distances ranging from 1.65–1.73 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Pd4+, and one Se5+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Pd4+, and one Se5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Na1+ and one Se5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Na1+ and one Se5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2PdSe2 by Materials Project

Na2PdSe2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to five Se2- atoms to form distorted corner-sharing NaSe5 trigonal bipyramids. There are a spread of Na–Se bond distances ranging from 2.96–3.09 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Na–Se bond distances ranging from 3.01–3.33 Å. Pd2+ is bonded in a square co-planar geometry to four Se2- atoms. All Pd–Se bond lengths are 2.51 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 8-coordinate geometry to six Na1+ and two equivalent Pd2+ atoms. In the second Se2- site, Se2- is bonded in a 7-coordinate geometry to five Na1+ and two equivalent Pd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu2PdO4 by Materials Project

Lu2PdO4 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Lu3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Lu–O bond distances ranging from 2.18–2.30 Å. Pd2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Pd–O bond lengths are 2.06 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Lu3+ atoms to form a mixture of distorted edge and corner-sharing OLu4 tetrahedra. In the second O2- site, O2- is bonded to two equivalent Lu3+ and two equivalent Pd2+ atoms to form a mixture of distorted edge and corner-sharing OLu2Pd2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Ionic Precursors Transformed Into Vinyl Acetate Synthesis Catalyst via Reaction-Driven Restructuring

Conventional preparation of supported bimetallic catalysts relies on solution-mediated metal salt immobilization and pre-formation of alloy nanoparticles before reaction. Here, we report a fundamentally different synthesis strategy of using a physical mixture of salt precursors to generate an active catalyst during reaction. The catalytic structure is generated in situ from Pd3(OAc)6, Au(OH)3, and KOAc through H2 treatment and reaction-driven restructuring under vinyl acetate monomer (VAM) synthesis conditions. Ascertained from in situ X-ray diffraction and operando infrared spectroscopy analyses, reduction treatment produces segregated Pd and Au domains, and subsequent exposure to a VAM reaction mixture triggers dynamic extraction of Pd from the metal surface. This latter process, mediated by acetate-assisted redox cycles, facilitates Pd migration toward Au domains to form a near-surface localized Pd50Au50 alloy phase. Monometallic Pd domains serve as a reservoir of Pd to the alloy phase, leading to and sustaining a more Pd-enriched active surface and a higher population of accessible Pd sites, compared to a conventionally prepared K-PdAu/SiO2 catalyst. Consequently, this leads to a twofold increase in the VAM formation rate, demonstrating highly active bimetallic catalysts can be generated through the gas-phase treatment of physically mixed ionic precursors.

Cha, Byeong Jun [Rice University]↗
NASA NTRS2010

Conditions of Core Formation in the Early Earth: Single Stage or Heterogeneous Accretion?

Since approx.1990 high pressure and temperature (PT) experiments on metal-silicate systems have showed that partition coefficients [D(met/sil)] for siderophile (iron-loving) elements are much different than those measured at low PT conditions [1,2]. The high PT data have been used to argue for a magma ocean during growth of the early Earth [3,4]. In the ensuing decades there have been hundreds of new experiments carried out and published on a wide range of siderophile elements (> 80 experiments published for Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd). At the same time several different models have been advanced to explain the siderophile elements in Earth's mantle: a) shallow depth magma ocean 25-30 GPa [3,5]; b) deep magma ocean; up to 50 GPa [6,7], and c) early reduced and later oxidized magma ocean [8,9]. Some studies have drawn conclusions based on a small subset of siderophile elements, or a set of elements that provides little leverage on the big picture (like slightly siderophile elements), and no single study has attempted to quantitatively explain more than 5 elements at a time. The purpose of this abstract is to identify issues that have lead to a difference in interpretation, and to present updated predictive expressions based on new experimental data. The resulting expressions will be applied to the siderophile element depletions in Earth's upper mantle.

Righter, Kevin↗
DOE OSTI2020

Materials Data on K2PdO2 by Materials Project

K2PdO2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. K1+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. There are four shorter (2.80 Å) and two longer (3.13 Å) K–O bond lengths. Pd2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Pd–O bond lengths are 2.09 Å. O2- is bonded in a 2-coordinate geometry to six equivalent K1+ and two equivalent Pd2+ atoms.

36 MATERIALS SCIENCE↗