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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Dimming the Lights: 2D Simulations of Deflagrations of Hybrid C/O/Ne White Dwarfs Using FLASH

The dimmest and most numerous outlier of the Type Ia supernova population, the Type Iax event, is increasingly being found in the results of observational campaigns. There is currently no single accepted model to describe these events. This 2D study explores the viability of modeling Type Iax events as a hybrid C/O/Ne white dwarf progenitor undergoing a deflagration using the multiphysics software FLASH. This hybrid was created using the stellar evolution code MESA, and its C-depleted core and mixed structure have demonstrated lower yields than traditional C/O progenitors in previous deflagration-to-detonation studies. To generate a sample, 30 “realizations” of this simulation were performed, the only difference being the shape of the initial match head used to start the deflagration. Consistent with earlier work, these realizations produce the familiar hot dense bound remnant surrounded by sparse ejecta. Our results indicate that the majority of the star remains unburned (∼70%) and bound (>90%). Our realizations produce total ejecta yields on the order of 10 −2 –10 −1 M ☉ , ejected 56 Ni yields on the order of 10 −4 –10 −2 M ☉ , and ejecta kinetic energies on the order of 10 48 –10 49 erg. Compared to yields inferred from recent observations of the dimmest Type Iax events—SN 2007qd, SN 2008ha, SN 2010ae, SN 2019gsc, SN 2019muj, SN 2020kyg, and SN 2021fcg—our simulation produces comparable 56 Ni yields but too-small total yields and kinetic energies. Reignition of the remnant is also seen in some realizations.

Hydrodynamical simulations↗
DOE OSTI2020

Materials Data on RbBiC4(SN)4 by Materials Project

RbC4Bi(NS)4 crystallizes in the orthorhombic P2_12_12 space group. The structure is three-dimensional. Rb1+ is bonded in a 12-coordinate geometry to four N3- atoms. There are two shorter (3.13 Å) and two longer (3.15 Å) Rb–N bond lengths. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.18 Å. The C–S bond length is 1.65 Å. In the second C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.18 Å. The C–S bond length is 1.64 Å. Bi3+ is bonded in a 8-coordinate geometry to four N3- and four S2- atoms. There are two shorter (2.71 Å) and two longer (2.93 Å) Bi–N bond lengths. There are two shorter (2.82 Å) and two longer (2.92 Å) Bi–S bond lengths. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted single-bond geometry to one Rb1+, one C4+, and one Bi3+ atom. In the second N3- site, N3- is bonded in a distorted single-bond geometry to one Rb1+, one C4+, and one Bi3+ atom. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to one C4+ and one Bi3+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to one C4+ and one Bi3+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1974

A search for X-rays from supernova 1972e with Uhuru and OSO-7

The results of observations performed with X-ray detectors aboard OSO-7 and Uhuru at 13 different times ranging from 16 months before to 2 years after Sn 1972e maximum light are reported. Only one possible (3.2 sigma) positive result was found. The absence of any sizable flux contradicts the model of Shklovsky and imposes limitations on the model of Colgate and McKee.

Canizares, C. R.↗
DOE OSTI2020

Nb 3 Sn multicell cavity coating system at Jefferson Lab

Superconducting radio frequency niobium cavities are the building blocks of modern accelerators for scientific applications. Lower surface resistance, higher fields, and high operating temperatures advance the reach of the future accelerators for scientific discovery as well as potentially enabling cost-effective industrial solutions. We describe the design and performance of an Nb 3 Sn coating system that converts the inner surface of niobium cavities to an Nb 3 Sn film. The niobium surface, heated by radiation from the niobium retort, is exposed to Sn and SnCl 2 vapor during the heat cycle, which results in about 2 μm Nb 3 Sn film on the niobium surface. Film composition and structure as well as radio frequency properties with 1-cell R&D cavities and 5-cell practical accelerator cavities are presented.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Grafted nickel-promoter catalysts for dry reforming of methane identified through high-throughput experimentation

High-throughput synthesis of a series of monometallic and bimetallic catalysts (45 bimetallic and 50 monometallic samples) consisting of nickel and one of nine different metal promoters (B, Co, Cu, Fe, Mg, Mn, Sn, V and Zn) supported on one of six different metal oxides alumina, ceria, magnesia, silica and titania) is carried out via organometallic grafting using a robotic platform. The catalysts are evaluated for their activity and selectivity for the dry reforming of methane at a feed ratio of CH 4 :CO 2 of 1 at 650–800 °C in a parallel flow reactor system. The type of oxide support prevails over the type of additive for both catalyst activity and stability. On Al 2 O 3 and MgO, Fe was found to be the best promoter; on SiO 2 , Cu is the best promoter at 700 °C and higher, while on TiO 2 , Mn is found to enhance the conversion at 800 °C. On CeO 2 , all additives except Fe have beneficial effects. Twenty-five catalysts show > 90% methane conversion with ten catalysts showing > 95% conversion at 800 °C with the H 2 :CO ratios ranging from 0.8 to 1.2. Amongst the ten highest performers, NiFe/Al 2 O 3 and NiFe/MgO are more active than Ni/Al 2 O 3 and Ni/MgO, respectively and were stable over a period of 25 h at 800 °C. Characterization on the as-prepared samples reveals highly dispersed phase, while after reduction in H 2 , highly dispersed and reduced nickel particles up to 10 nm are formed. The particles do not increase in size under dry reforming reaction conditions at 800 °C. An increased hydrogen consumption observed during H 2 -TPR of the nickel particles is positively correlated with methane conversion for Al 2 O 3 -based catalysts. The resistance to deactivation by coking and variation in coke structure are investigated by spectroscopic and microscopic methods to identify the relationship between metal promoters, alloy formation, and type of surface carbon deposits. Carbon whiskers were observed on the ten selected spent samples and are preferentially deposited on Ni rather than on the promoters. Carbon nanotube formation and metal particle removal from support were not observed to cause deactivation while amorphous carbon formation was clearly linked to catalyst deactivation, as amorphous carbon could encapsulate nickel, either on the support or at the end of the carbon nanotube. Furthermore, the organometallic grafting technique is an efficient and suitable technique for synthesizing highly dispersed and homogeneous phases which lead to high conversion and high durability for dry reforming of methane.

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

Materials Data on Fe6Sn2(CO)23 by Materials Project

(Fe(CO)4)4(Fe(CO)3)2(Sn)2CO crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four 7440-31-5 molecules, two formaldehyde molecules, four Fe(CO)3 clusters, and eight Fe(CO)4 clusters. In two of the Fe(CO)3 clusters, Fe3+ is bonded in a 3-coordinate geometry to three C+0.87+ atoms. There is one shorter (1.78 Å) and two longer (1.79 Å) Fe–C bond length. There are three inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.17 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In two of the Fe(CO)3 clusters, Fe3+ is bonded in a 3-coordinate geometry to three C+0.87+ atoms. There is two shorter (1.79 Å) and one longer (1.80 Å) Fe–C bond length. There are three inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In two of the Fe(CO)4 clusters, Fe3+ is bonded in a distorted see-saw-like geometry to four C+0.87+ atoms. There are a spread of Fe–C bond distances ranging from 1.77–1.81 Å. There are four inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In two of the Fe(CO)4 clusters, Fe3+ is bonded in a see-saw-like geometry to four C+0.87+ atoms. There are a spread of Fe–C bond distances ranging from 1.77–1.81 Å. There are four inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In four of the Fe(CO)4 clusters, Fe3+ is bonded in a see-saw-like geometry to four C+0.87+ atoms. There are a spread of Fe–C bond distances ranging from 1.77–1.81 Å. There are four inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The whisper of a whimper of a bang: 2400 d of the Type Ia SN 2011fe reveals the decay of 55Fe

ABSTRACT We analyse new multifilter Hubble Space Telescope (HST) photometry of the normal Type Ia supernova (SN Ia) 2011fe out to ≈2400 d after maximum light, the latest observations to date of a SN Ia. We model the pseudo-bolometric light curve with a simple radioactive decay model and find energy input from both 57Co and 55Fe are needed to power the late-time luminosity. This is the first detection of 55Fe in a SN Ia. We consider potential sources of contamination such as a surviving companion star or delaying the deposition time-scale for 56Co positrons but these scenarios are ultimately disfavored. The relative isotopic abundances place direct constraints on the burning conditions experienced by the white dwarf (WD). Additionally, we place a conservative upper limit of <10−3 M⊙ on the synthesized mass of 44Ti. Only two classes of explosion models are currently consistent with all observations of SN 2011fe: (1) the delayed detonation of a low-ρc, near-MCh (1.2–1.3 M⊙) WD, or (2) a sub-MCh (1.0–1.1 M⊙) WD experiencing a thin-shell double detonation.

Astronomy & Astrophysics↗
DOE OSTI2020

Materials Data on K2PdC4(SN)4 by Materials Project

K2PdC4(NS)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. K1+ is bonded in a 4-coordinate geometry to five N3- and three S2- atoms. There are a spread of K–N bond distances ranging from 2.78–3.27 Å. There are a spread of K–S bond distances ranging from 3.41–3.73 Å. Pd2+ is bonded in a square co-planar geometry to four S2- atoms. All Pd–S bond lengths are 2.39 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.18 Å. The C–S bond length is 1.66 Å. In the second C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.19 Å. The C–S bond length is 1.65 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a 1-coordinate geometry to three equivalent K1+ and one C4+ atom. In the second N3- site, N3- is bonded in a 1-coordinate geometry to two equivalent K1+ and one C4+ atom. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to two equivalent K1+, one Pd2+, and one C4+ atom. In the second S2- site, S2- is bonded in a distorted water-like geometry to one K1+, one Pd2+, and one C4+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Recrystallization as a controlling process in the wear of some f.c.c. metals

Detailed examination of copper specimens after sliding against 440 C steel in liquid methane at speeds up to 25 m/s and loads of up to 2 kg showed the metal comprising the wear surface to possess a fine cell recrystallized structure. Wear proceeded by the plastic shearing of metal in this near surface region without the occurrence of visible metal transfer. A dynamic balance between the intense shear process at the surface and the nucleation of recrystallized grains was proposed to account for the behavior of the metal at the wear surface. Sliding wear experiments were also conducted on Ag, Cu-10% Al, Cu-10% Sn, Ni and Al. It was found that low wear and the absence of heavy metal transfer were associated with those metals observed to undergo recrystallization nucleation without prior recovery.

Bill, R. C.↗
NASA NTRS1990

Platinized tin oxide catalysts for CO2 lasers: Effects of pretreatment

Platinized tin oxide surfaces used for low-temperature CO oxidation in CO2 lasers have been characterized before and after reduction in CO at 125 and 250 C using ion scattering spectroscopy (ISS) and X ray photoelectron spectroscopy (XPS). XPS indicates that the Pt is present initially as PtO2. Reduction at 125 C converts the PtO2 to Pt(OH)2 while reduction at 250 C converts the PtO2 to metallic Pt. ISS shows that the Pt in the outermost atomic layer of the catalyst is mostly covered by substrate species during the 250 C reduction. Both the ISS and XPS results are consistent with Pt/Sn alloy formation. The surface dehydration and migration of substrate species over surface Pt and Sn appear to explain why a CO pretreatment at 250 C produces inferior CO oxidation activities compared to a 125 C pretreatment.

Gardner, Steven D.↗
NASA NTRS1989

Platinized tin oxide catalysts for CO2 lasers - Effects of pretreatment

Platinized tin oxide surfaces used for low-temperature CO oxidation in CO2 lasers have been characterized before and after reduction in CO at 125 and 250 C using ion scattering spectroscopy (ISS) and X-ray photoelectron spectroscopy (XPS). XPS indicates that the Pt is present initially as Pto2. Reduction at 125 C converts the PtO2 to Pt(OH)2 while reduction at 250 C converts the PtO2 to metallic Pt. ISS shows that the Pt in the outermost atomic layer of the catalyst is mostly covered by substrate species during the 250 C reduction. Both the ISS and XPS results are consistent with Pt/Sn alloy formation. The surface dehydration and migration of substrate species over surface Pt and Sn appear to explain why a CO pretreatment at 250 C produces inferior CO oxidation activities compared to a 125 C pretreatment.

Gardner, Steven D.↗
DOE OSTI2021

Revealing pressure-driven structural transitions in the hybrid improper ferroelectric Sr 3 Sn 2 O 7

In this work, we combine diamond anvil cell techniques and synchrotron-based infrared spectroscopy with a detailed symmetry analysis and lattice dynamics calculations to uncover a series of pressure induced structural phase transitions in the hybrid improper ferroelectric Sr 3 Sn 2 O 7 . The microscopic character of each high pressure phase is determined by comparing the measured spectrum with the predicted vibrational patterns of several related but distinct candidate space groups. Our analysis reveals a sequence of compression-induced transitions from A2 1 am ↔ Pnab ↔ Acaa ↔ I4/mmm at room temperature. Remarkably, this space group progression matches the sequence of temperature-dependent structural transitions observed in Sr 3 Sn 2 O 7 between 77 and 1000 K. Other hybrid improper ferroelectrics display a similar set of transitions, suggesting that pressure and probably strain will be very effective tuning parameters for this entire class of materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1987

Detection of a very bright source close to the LMC supernova SN 1987A

High angular resolution observations of the supernova in the Large Magellanic Cloud, SN 1987A, have revealed a bright source separated from the SN by approximately 60 mas with a magnitude difference of 2.7 at 656 nm (H-alpha). Speckle imaging techniques were applied to data recorded with the CfA two-dimensional photon counting detector on the CTIO 4 m telescope on March 25 and April 2 to allow measurements in H-alpha on both nights and at 533 nm and 450 nm on the second night. The nature of this object is as yet unknown, though it is almost certainly a phenomenon related to the SN.

Nisenson, P.↗
DOE OSTI2020

Materials Data on H20RuC6NO14 by Materials Project

RuH12(C2O7)2(CH3)2NH2 is beta Sn-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is zero-dimensional and consists of four dimethylazanium molecules and four RuH12(C2O7)2 clusters. In each RuH12(C2O7)2 cluster, Ru3+ is bonded in an octahedral geometry to six O2- atoms. There are two shorter (2.02 Å) and four longer (2.07 Å) Ru–O bond lengths. C+1.33+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.25 Å) and one longer (1.30 Å) C–O bond length. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.02 Å) and one longer (1.58 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.02 Å) and one longer (1.60 Å) H–O bond length. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms. In the second O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ru3+ and two H1+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ru3+ and one C+1.33+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RbCdC3(SN)3 by Materials Project

RbCdC3(NS)3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Rb1+ is bonded in a 8-coordinate geometry to three N3- and five S2- atoms. There are a spread of Rb–N bond distances ranging from 3.02–3.36 Å. There are a spread of Rb–S bond distances ranging from 3.56–3.78 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in an octahedral geometry to four N3- and two equivalent S2- atoms. There are two shorter (2.32 Å) and two longer (2.35 Å) Cd–N bond lengths. Both Cd–S bond lengths are 2.78 Å. In the second Cd2+ site, Cd2+ is bonded in an octahedral geometry to two equivalent N3- and four S2- atoms. Both Cd–N bond lengths are 2.33 Å. There are two shorter (2.75 Å) and two longer (2.80 Å) Cd–S bond lengths. There are three inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.19 Å. The C–S bond length is 1.63 Å. In the second C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.19 Å. The C–S bond length is 1.63 Å. In the third C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.18 Å. The C–S bond length is 1.64 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded in a 3-coordinate geometry to one Rb1+, one Cd2+, and one C4+ atom. In the second N3- site, N3- is bonded in a distorted bent 150 degrees geometry to one Rb1+, one Cd2+, and one C4+ atom. In the third N3- site, N3- is bonded in a 2-coordinate geometry to one Rb1+, one Cd2+, and one C4+ atom. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to two equivalent Rb1+, one Cd2+, and one C4+ atom. In the second S2- site, S2- is bonded in a 2-coordinate geometry to one Rb1+, one Cd2+, and one C4+ atom. In the third S2- site, S2- is bonded in a 4-coordinate geometry to two equivalent Rb1+, one Cd2+, and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3SnPCO7 by Materials Project

Na3SnCPO7 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.25–2.78 Å. In the second Na1+ site, Na1+ is bonded to five O2- atoms to form distorted NaO5 trigonal bipyramids that share corners with three equivalent PO4 tetrahedra and edges with two equivalent NaO5 trigonal bipyramids. There are a spread of Na–O bond distances ranging from 2.33–2.62 Å. Sn2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Sn–O bond distances ranging from 2.44–2.55 Å. C4+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of C–O bond distances ranging from 1.29–1.32 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with six equivalent NaO5 trigonal bipyramids. There is two shorter (1.56 Å) and two longer (1.57 Å) P–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Sn2+, and one C4+ atom. In the second O2- site, O2- is bonded to three Na1+ and one C4+ atom to form distorted edge-sharing ONa3C tetrahedra. In the third O2- site, O2- is bonded in a distorted single-bond geometry to three Na1+, one Sn2+, and one C4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Sn2+, and one P5+ atom. In the fifth O2- site, O2- is bonded to two equivalent Na1+, one Sn2+, and one P5+ atom to form distorted edge-sharing ONa2SnP tetrahedra. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Na1+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Eu 5 Al 3 Sb 6 : Al 4 Tetrahedra Embedded in a Rock-Salt-Like Structure

The new Eu 5 Al 3 Sb 6 phase has been successfully synthesized as a pure phase through Sn flux methods yielding large, high-quality crystals. This structure type features disordered Al clusters that appear in the form of dual tetrahedra. It crystallizes in the monoclinic C2/m space group exhibiting a rock-salt-like Eu–Sb framework with [Al 4 ] tetrahedra replacing some of the cationic Eu atoms (space group: C2/m, a = 8.151(1) Å, b = 14.181(2) Å, c = 8.145(1) Å, β = 109.577(2)°). The structure models the [Al 4 ] as dual tetrahedra with the Al atom sites 37.5% occupied along with Eu present on the central site at 8% occupancy and the remainder of the site being vacant. The presence of the [Al 4 ] cluster is further supported by HRTEM. Electronic structure calculations show that this material is a semimetal with observed band crossings close to the Fermi level. Strong Al–Sb antibonding interactions were found from COHP calculations close to the Fermi level and provide the rationale for the deficiency of the Al cluster. Mössbauer spectroscopy on Eu-151 and Sb-121 provides oxidation states of 2+ and 3– along with the local environment. Magnetic susceptibility measurements can be described well with a Curie–Weiss law where an effective moment of 7.80 μB/mol Eu is obtained, consistent with Eu 2+ , and show canted antiferromagnetic behavior below 10 K. Temperature dependent resistivity shows a Kondo-like low-temperature upturn caused by enhanced scattering of the itinerant electrons with the 4f orbitals of Eu.

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

Evolution of collectivity in 118 Xe

A recoil-distance Doppler shift experiment has been performed using the Pd 102 ( F 19 , p 2 n ) reaction at a beam energy of 73 MeV to measure the lifetime of excited states in Xe 118 . Additionally, the differential decay-curve method using γ γ coincidences and a gating procedure that allows to extract the lifetime without feeding assumptions has been employed. The lifetimes obtained for the yrast states up to spin-parity 8 + are compared with interacting boson model calculations and Xe 118 can be classified as a transitional nucleus between the spherical and a deformed shape. Systematics of the B ( E 2 ) values for the 2 + → 0 + and 4 + → 2 + transitions in the isotopic chains of tin, tellurium and xenon are presented. It is proposed that a “critical point” exists at which the B ( E 2 ; 4 + → 2 + ) / B ( E 2 ; 2 + → 0 + ) ratio drops to unity for lower neutron numbers within the isotopic chain. The position of the “critical point” varies with proton number, i.e., it is presumed to be located at the same mass number A = 114 in the Sn, Te, and Xe isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗