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At least 1,567 records · Page 87
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DOE OSTI2020

Materials Data on Ag6SnSb by Materials Project

Ag6SnSb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are four inequivalent Ag sites. In the first Ag site, Ag is bonded to eight Ag, two equivalent Sn, and two equivalent Sb atoms to form AgAg8Sn2Sb2 cuboctahedra that share corners with four equivalent SbAg12 cuboctahedra, corners with fourteen AgAg8Sn2Sb2 cuboctahedra, edges with two equivalent SbAg12 cuboctahedra, edges with four equivalent SnAg12 cuboctahedra, edges with twelve AgAg8Sn2Sb2 cuboctahedra, faces with two equivalent SnAg12 cuboctahedra, faces with two equivalent SbAg12 cuboctahedra, and faces with sixteen AgAg8Sn2Sb2 cuboctahedra. There are a spread of Ag–Ag bond distances ranging from 2.96–3.09 Å. Both Ag–Sn bond lengths are 3.02 Å. There are one shorter (3.02 Å) and one longer (3.09 Å) Ag–Sb bond lengths. In the second Ag site, Ag is bonded to eight Ag, two equivalent Sn, and two equivalent Sb atoms to form AgAg8Sn2Sb2 cuboctahedra that share corners with four equivalent SnAg12 cuboctahedra, corners with fourteen AgAg8Sn2Sb2 cuboctahedra, edges with two equivalent SnAg12 cuboctahedra, edges with four equivalent SbAg12 cuboctahedra, edges with twelve AgAg8Sn2Sb2 cuboctahedra, faces with two equivalent SnAg12 cuboctahedra, faces with two equivalent SbAg12 cuboctahedra, and faces with sixteen AgAg8Sn2Sb2 cuboctahedra. There are a spread of Ag–Ag bond distances ranging from 3.00–3.12 Å. There are one shorter (3.01 Å) and one longer (3.08 Å) Ag–Sn bond lengths. Both Ag–Sb bond lengths are 3.03 Å. In the third Ag site, Ag is bonded to eight Ag, two equivalent Sn, and two equivalent Sb atoms to form AgAg8Sn2Sb2 cuboctahedra that share corners with eight equivalent SnAg12 cuboctahedra, corners with ten AgAg8Sn2Sb2 cuboctahedra, edges with eighteen AgAg8Sn2Sb2 cuboctahedra, faces with two equivalent SnAg12 cuboctahedra, faces with four equivalent SbAg12 cuboctahedra, and faces with fourteen AgAg8Sn2Sb2 cuboctahedra. Both Ag–Sn bond lengths are 3.07 Å. Both Ag–Sb bond lengths are 3.02 Å. In the fourth Ag site, Ag is bonded to eight Ag, two equivalent Sn, and two equivalent Sb atoms to form AgAg8Sn2Sb2 cuboctahedra that share corners with eight equivalent SbAg12 cuboctahedra, corners with ten AgAg8Sn2Sb2 cuboctahedra, edges with eighteen AgAg8Sn2Sb2 cuboctahedra, faces with two equivalent SbAg12 cuboctahedra, faces with four equivalent SnAg12 cuboctahedra, and faces with fourteen AgAg8Sn2Sb2 cuboctahedra. Both Ag–Sn bond lengths are 3.01 Å. Both Ag–Sb bond lengths are 3.07 Å. Sn is bonded to twelve Ag atoms to form SnAg12 cuboctahedra that share corners with two equivalent SnAg12 cuboctahedra, corners with sixteen AgAg8Sn2Sb2 cuboctahedra, edges with two equivalent SnAg12 cuboctahedra, edges with four equivalent SbAg12 cuboctahedra, edges with twelve AgAg8Sn2Sb2 cuboctahedra, faces with two equivalent SnAg12 cuboctahedra, faces with four equivalent SbAg12 cuboctahedra, and faces with fourteen AgAg8Sn2Sb2 cuboctahedra. Sb is bonded to twelve Ag atoms to form SbAg12 cuboctahedra that share corners with two equivalent SbAg12 cuboctahedra, corners with sixteen AgAg8Sn2Sb2 cuboctahedra, edges with two equivalent SbAg12 cuboctahedra, edges with four equivalent SnAg12 cuboctahedra, edges with twelve AgAg8Sn2Sb2 cuboctahedra, faces with two equivalent SbAg12 cuboctahedra, faces with four equivalent SnAg12 cuboctahedra, and faces with fourteen AgAg8Sn2Sb2 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2Al3Sn by Materials Project

La2Al3Sn is hexagonal omega structure-derived structured and crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are two inequivalent La sites. In the first La site, La is bonded to ten Al and two equivalent Sn atoms to form a mixture of edge and face-sharing LaAl10Sn2 cuboctahedra. There are a spread of La–Al bond distances ranging from 3.34–3.43 Å. Both La–Sn bond lengths are 3.46 Å. In the second La site, La is bonded to eight Al and four equivalent Sn atoms to form a mixture of edge and face-sharing LaAl8Sn4 cuboctahedra. There are a spread of La–Al bond distances ranging from 3.38–3.52 Å. All La–Sn bond lengths are 3.43 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to six La and three Al atoms. There are one shorter (2.54 Å) and two longer (2.55 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 2-coordinate geometry to six La, one Al, and two equivalent Sn atoms. Both Al–Sn bond lengths are 2.67 Å. In the third Al site, Al is bonded in a 1-coordinate geometry to six La, two equivalent Al, and one Sn atom. The Al–Sn bond length is 2.67 Å. Sn is bonded in a 3-coordinate geometry to six La and three Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgSn by Materials Project

MgSn crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 6-coordinate geometry to six Sn atoms. There are a spread of Mg–Sn bond distances ranging from 3.05–3.33 Å. In the second Mg site, Mg is bonded in a 8-coordinate geometry to eight Sn atoms. There are a spread of Mg–Sn bond distances ranging from 3.06–3.29 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 8-coordinate geometry to eight Mg atoms. In the second Sn site, Sn is bonded in a 6-coordinate geometry to six Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni9(SnS)2 by Materials Project

Ni9(SnS)2 crystallizes in the tetragonal I-4m2 space group. The structure is three-dimensional. there are five inequivalent Ni sites. In the first Ni site, Ni is bonded to eight Ni and four equivalent Sn atoms to form NiNi8Sn4 cuboctahedra that share corners with four equivalent NiNi8Sn4 cuboctahedra, edges with eight equivalent NiNi8Sn4 cuboctahedra, edges with eight equivalent SnNi12 cuboctahedra, faces with four equivalent SnNi12 cuboctahedra, and faces with twelve NiNi8Sn4 cuboctahedra. There are four shorter (2.60 Å) and four longer (2.62 Å) Ni–Ni bond lengths. All Ni–Sn bond lengths are 2.64 Å. In the second Ni site, Ni is bonded to eight Ni and four equivalent Sn atoms to form NiNi8Sn4 cuboctahedra that share corners with eight equivalent NiNi8Sn4 cuboctahedra, edges with four equivalent SnNi12 cuboctahedra, edges with eight equivalent NiNi8Sn4 cuboctahedra, faces with four equivalent SnNi12 cuboctahedra, and faces with nine NiNi8Sn4 cuboctahedra. There are two shorter (2.68 Å) and two longer (2.70 Å) Ni–Ni bond lengths. All Ni–Sn bond lengths are 2.63 Å. In the third Ni site, Ni is bonded in a distorted water-like geometry to two equivalent Ni, two equivalent Sn, and two equivalent S atoms. Both Ni–Sn bond lengths are 2.63 Å. Both Ni–S bond lengths are 2.25 Å. In the fourth Ni site, Ni is bonded in a distorted bent 120 degrees geometry to two equivalent Ni, two equivalent Sn, and two equivalent S atoms. Both Ni–Sn bond lengths are 2.66 Å. Both Ni–S bond lengths are 2.23 Å. In the fifth Ni site, Ni is bonded to four equivalent S atoms to form corner-sharing NiS4 tetrahedra. All Ni–S bond lengths are 2.25 Å. Sn is bonded to twelve Ni atoms to form SnNi12 cuboctahedra that share corners with eight equivalent SnNi12 cuboctahedra, edges with twelve NiNi8Sn4 cuboctahedra, faces with five equivalent SnNi12 cuboctahedra, and faces with eight NiNi8Sn4 cuboctahedra. S is bonded in a distorted hexagonal planar geometry to six Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiTbSn2 by Materials Project

LiTbSn2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Li is bonded in a 5-coordinate geometry to four equivalent Tb and five Sn atoms. All Li–Tb bond lengths are 3.39 Å. There are a spread of Li–Sn bond distances ranging from 2.48–2.67 Å. Tb is bonded in a 4-coordinate geometry to four equivalent Li and ten Sn atoms. There are a spread of Tb–Sn bond distances ranging from 3.36–3.60 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a distorted single-bond geometry to one Li and six equivalent Tb atoms. In the second Sn site, Sn is bonded to four equivalent Li and four equivalent Tb atoms to form a mixture of distorted edge and face-sharing SnLi4Tb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KMg6Sn by Materials Project

KMg6Sn crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. K is bonded to ten Mg and two equivalent Sn atoms to form a mixture of corner and face-sharing KMg10Sn2 cuboctahedra. There are a spread of K–Mg bond distances ranging from 3.34–3.52 Å. Both K–Sn bond lengths are 3.33 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent K, eight Mg, and one Sn atom. There are a spread of Mg–Mg bond distances ranging from 3.20–3.37 Å. The Mg–Sn bond length is 3.35 Å. In the second Mg site, Mg is bonded in a 4-coordinate geometry to two equivalent K, three Mg, and two equivalent Sn atoms. The Mg–Mg bond length is 3.26 Å. Both Mg–Sn bond lengths are 3.18 Å. In the third Mg site, Mg is bonded in a 2-coordinate geometry to six Mg and two equivalent Sn atoms. Both Mg–Mg bond lengths are 3.33 Å. Both Mg–Sn bond lengths are 3.38 Å. In the fourth Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent K and eight Mg atoms. Sn is bonded in a 10-coordinate geometry to two equivalent K and eight Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd2Zn5Sn by Materials Project

Nd2Zn5Sn crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Nd sites. In the first Nd site, Nd is bonded in a 11-coordinate geometry to thirteen Zn and two equivalent Sn atoms. There are a spread of Nd–Zn bond distances ranging from 3.14–3.34 Å. Both Nd–Sn bond lengths are 3.36 Å. In the second Nd site, Nd is bonded in a 6-coordinate geometry to ten Zn and four equivalent Sn atoms. There are a spread of Nd–Zn bond distances ranging from 3.23–3.64 Å. All Nd–Sn bond lengths are 3.32 Å. There are three inequivalent Zn sites. In the first Zn site, Zn is bonded in a 10-coordinate geometry to four Nd and six Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.56–2.91 Å. In the second Zn site, Zn is bonded in a 1-coordinate geometry to five Nd, four Zn, and one Sn atom. The Zn–Zn bond length is 2.56 Å. The Zn–Sn bond length is 2.71 Å. In the third Zn site, Zn is bonded in a 1-coordinate geometry to five Nd, six Zn, and one Sn atom. The Zn–Sn bond length is 2.64 Å. Sn is bonded in a 9-coordinate geometry to six Nd and three Zn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3Ag3Sn2 by Materials Project

LiAg2Li2AgSn2 crystallizes in the trigonal R3m space group. The structure is three-dimensional and consists of three LiAg2 sheets oriented in the (0, 0, 1) direction and one Li2AgSn2 framework. In each LiAg2 sheet, Li is bonded to four Ag atoms to form distorted corner-sharing LiAg4 tetrahedra. There are one shorter (2.85 Å) and three longer (2.88 Å) Li–Ag bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded in a 3-coordinate geometry to three equivalent Li atoms. In the second Ag site, Ag is bonded in a distorted single-bond geometry to one Li atom. In the Li2AgSn2 framework, there are two inequivalent Li sites. In the first Li site, Li is bonded in a 5-coordinate geometry to one Ag and four Sn atoms. The Li–Ag bond length is 2.86 Å. There are one shorter (2.86 Å) and three longer (2.87 Å) Li–Sn bond lengths. In the second Li site, Li is bonded in a 7-coordinate geometry to three equivalent Ag and four Sn atoms. All Li–Ag bond lengths are 2.88 Å. There are one shorter (2.88 Å) and three longer (2.90 Å) Li–Sn bond lengths. Ag is bonded to four Li atoms to form distorted AgLi4 tetrahedra that share corners with four equivalent SnLi4 tetrahedra, corners with six equivalent AgLi4 tetrahedra, and edges with three equivalent SnLi4 tetrahedra. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to four Li atoms. In the second Sn site, Sn is bonded to four Li atoms to form distorted SnLi4 tetrahedra that share corners with four equivalent AgLi4 tetrahedra, corners with six equivalent SnLi4 tetrahedra, and edges with three equivalent AgLi4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2Zn5Sn by Materials Project

La2Zn5Sn crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent La sites. In the first La site, La is bonded in a 11-coordinate geometry to thirteen Zn and two equivalent Sn atoms. There are a spread of La–Zn bond distances ranging from 3.19–3.34 Å. Both La–Sn bond lengths are 3.41 Å. In the second La site, La is bonded in a 6-coordinate geometry to ten Zn and four equivalent Sn atoms. There are a spread of La–Zn bond distances ranging from 3.27–3.67 Å. All La–Sn bond lengths are 3.37 Å. There are three inequivalent Zn sites. In the first Zn site, Zn is bonded in a 10-coordinate geometry to four La and six Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.59–2.98 Å. In the second Zn site, Zn is bonded in a 1-coordinate geometry to five La, four Zn, and one Sn atom. The Zn–Zn bond length is 2.58 Å. The Zn–Sn bond length is 2.73 Å. In the third Zn site, Zn is bonded in a 1-coordinate geometry to five La, six Zn, and one Sn atom. The Zn–Sn bond length is 2.67 Å. Sn is bonded in a 9-coordinate geometry to six La and three Zn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Superconducting properties of commercially available solders for low-field applications

Solders with superconducting transitions around 4K are useful in low magnetic field environments for AC current leads or in electrical and mechanical bonds. Accurate knowledge of these solders’ superconducting properties is essential for improving high precision experiments. We have measured the electrical resistance of five commercially-available eutectic or near-eutectic solders: 50%Sn-50%Pb, 60%Sn-40%Pb, 60%Sn-40%Pb-0.3%Sb, 52%In-48%Sn, and 96.5%Sn-3.5%Ag, down to 2.3K and in applied magnetic fields from 0 to 0.1 T . We report critical temperatures T c (B), 90%–10% transition widths ΔT c , and zero-temperature critical fields B c,0 . Our best candidate for low-loss AC current wiring in low fields is 50%Sn-50%Pb, which has a zero-field T c,0 = 7.1K (with ΔT c = 0.6 K), and remained high at T c (0.1 T) = 6.9K (ΔT c = 0.6K ). We also report, for the first time, T c and B c of 60%Sn-40%Pb-0.3%Sb and B c,0 of 96.5%Sn-3.5%Ag. Our T c,0 - 3.31K (ΔT c = 0.08K) for 96.5%Sn-3.5%Ag disagrees with a widely adopted value.

Hickman, C. [North Carolina State University, Rale↗
DOE OSTI2021

Expanding the Ambient-Pressure Phase Space of CaFe 2 O 4 -Type Sodium Postspinel Host–Guest Compounds

CaFe 2 O 4 -type sodium postspinels (Na-CFs), with Na + occupying tunnel sites, are of interest as prospective battery electrodes. While many compounds of this structure type require high-pressure synthesis, several compounds are known to form at ambient pressure. Here we report a large expansion of the known Na-CF phase space at ambient pressure, having successfully synthesized NaCrTiO 4 , NaRhTiO 4 , NaCrSnO 4 , NaInSnO 4 , NaMg 0.5 Ti 1.5 O 4 , NaFe 0.5 Ti 1.5 O 4 , NaMg 0.5 Sn 1.5 O 4 , NaMn 0.5 Sn 1.5 O 4 , NaFe 0.5 Sn 1.5 O 4 , NaCo 0.5 Sn 1.5 O 4 , NaNi 0.5 Sn 1.5 O 4 , NaCu 0.5 Sn 1.5 O 4 , NaZn 0.5 Sn 1.5 O 4 , NaCd 0.5 Sn 1.5 O 4 , NaSc 1.5 Sb 0.5 O 4 , Na 1.16 In 1.18 Sb 0.66 O 4 , and several solid solutions. In contrast to earlier reports, even cations that are strongly Jahn–Teller active (e.g., Mn 3+ and Cu 2+ ) can form Na-CFs at ambient pressure when combined with Sn 4+ rather than with the smaller Ti 4+ . Order and disorder are probed at the average and local length-scales with synchrotron powder X-ray diffraction and solid-state NMR spectroscopy. Strong ordering of framework cations between the two framework sites is not observed, except in the case of Na 1.16 In 1.18 Sb 0.66 O 4 . This compound is the first example of an Na-CF that contains Na + in both the tunnel and framework sites, reminiscent of Li-rich spinels. Trends in the thermodynamic stability of the new compounds are explained on the basis of crystal-chemistry and density functional theory (DFT). Further DFT calculations examine the relative stability of the CF versus spinel structures at various degrees of sodium extraction in the context of electrochemical battery reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Isolated copper–tin atomic interfaces tuning electrocatalytic CO 2 conversion

Direct experimental observations of the interface structure can provide vital insights into heterogeneous catalysis. Examples of interface design based on single atom and surface science are, however, extremely rare. Here, we report Cu–Sn single-atom surface alloys, where isolated Sn sites with high surface densities (up to 8%) are anchored on the Cu host, for efficient electrocatalytic CO 2 reduction. The unique geometric and electronic structure of the Cu–Sn surface alloys (Cu 97 Sn 3 and Cu 99 Sn 1 ) enables distinct catalytic selectivity from pure Cu 100 and Cu 70 Sn 30 bulk alloy. The Cu 97 Sn 3 catalyst achieves a CO Faradaic efficiency of 98% at a tiny overpotential of 30 mV in an alkaline flow cell, where a high CO current density of 100 mA cm –2 is obtained at an overpotential of 340 mV. Density functional theory simulation reveals that it is not only the elemental composition that dictates the electrocatalytic reactivity of Cu–Sn alloys; the local coordination environment of atomically dispersed, isolated Cu–Sn bonding plays the most critical role.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Discovery and construction of surface kagome electronic states induced by p-d electronic hybridization in Co3Sn2S2

Abstract Kagome-lattice materials possess attractive properties for quantum computing applications, but their synthesis remains challenging. Herein, based on the compelling identification of the two cleavable surfaces of Co 3 Sn 2 S 2 , we show surface kagome electronic states (SKESs) on a Sn-terminated triangular Co 3 Sn 2 S 2 surface. Such SKESs are imprinted by vertical p-d electronic hybridization between the surface Sn (subsurface S) atoms and the buried Co kagome-lattice network in the Co 3 Sn layer under the surface. Owing to the subsequent lateral hybridization of the Sn and S atoms in a corner-sharing manner, the kagome symmetry and topological electronic properties of the Co 3 Sn layer is proximate to the Sn surface. The SKESs and both hybridizations were verified via qPlus non-contact atomic force microscopy (nc-AFM) and density functional theory calculations. The construction of SKESs with tunable properties can be achieved by the atomic substitution of surface Sn (subsurface S) with other group III-V elements (Se or Te), which was demonstrated theoretically. This work exhibits the powerful capacity of nc-AFM in characterizing localized topological states and reveals the strategy for synthesis of large-area transition-metal-based kagome-lattice materials using conventional surface deposition techniques.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Redshift evolution of the underlying type Ia supernova stretch distribution

The detailed nature of type Ia supernovae (SNe Ia) remains uncertain, and as survey statistics increase, the question of astrophysical systematic uncertainties arises, notably that of the evolution of SN Ia populations. We study the dependence on redshift of the SN Ia SALT2.4 light-curve stretch, which is a purely intrinsic SN property, to probe its potential redshift drift. The SN stretch has been shown to be strongly correlated with the SN environment, notably with stellar age tracers. We modeled the underlying stretch distribution as a function of redshift, using the evolution of the fraction of young and old SNe Ia as predicted using the SNfactory dataset, and assuming a constant underlying stretch distribution for each age population consisting of Gaussian mixtures. We tested our prediction against published samples that were cut to have marginal magnitude selection effects, so that any observed change is indeed astrophysical and not observational in origin. In this first study, there are indications that the underlying SN Ia stretch distribution evolves as a function of redshift, and that the age drifting model is a better description of the data than any time-constant model, including the sample-based asymmetric distributions that are often used to correct Malmquist bias at a significance higher than 5σ. The favored underlying stretch model is a bimodal one, composed of a high-stretch mode shared by both young and old environments, and a low-stretch mode that is exclusive to old environments. The precise effect of the redshift evolution of the intrinsic properties of a SN Ia population on cosmology remains to be studied. The astrophysical drift of the SN stretch distribution does affect current Malmquist bias corrections, however, and thereby the distances that are derived based on SN that are affected by observational selection effects. We highlight that this bias will increase with surveys covering increasingly larger redshift ranges, which is particularly important for the Large Synoptic Survey Telescope.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

The Dark Energy Survey supernova programme: modelling selection efficiency and observed core-collapse supernova contamination

ABSTRACT The analysis of current and future cosmological surveys of Type Ia supernovae (SNe Ia) at high redshift depends on the accurate photometric classification of the SN events detected. Generating realistic simulations of photometric SN surveys constitutes an essential step for training and testing photometric classification algorithms, and for correcting biases introduced by selection effects and contamination arising from core-collapse SNe in the photometric SN Ia samples. We use published SN time-series spectrophotometric templates, rates, luminosity functions, and empirical relationships between SNe and their host galaxies to construct a framework for simulating photometric SN surveys. We present this framework in the context of the Dark Energy Survey (DES) 5-yr photometric SN sample, comparing our simulations of DES with the observed DES transient populations. We demonstrate excellent agreement in many distributions, including Hubble residuals, between our simulations and data. We estimate the core collapse fraction expected in the DES SN sample after selection requirements are applied and before photometric classification. After testing different modelling choices and astrophysical assumptions underlying our simulation, we find that the predicted contamination varies from 7.2 to 11.7 per cent, with an average of 8.8 per cent and an r.m.s. of 1.1 per cent. Our simulations are the first to reproduce the observed photometric SN and host galaxy properties in high-redshift surveys without fine-tuning the input parameters. The simulation methods presented here will be a critical component of the cosmology analysis of the DES photometric SN Ia sample: correcting for biases arising from contamination, and evaluating the associated systematic uncertainty.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

First β-decay spectroscopy of 135 In and new β-decay branches of 134 In

The β decay of the neutron-rich 134 In and 135 In was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number Z=50 above the N=82 shell. The β-delayed γ-ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three β-decay branches of 134 In were established, two of which were observed for the first time. Population of neutron-unbound states decaying via γ rays was identified in the two daughter nuclei of 134 In, 134 Sn and 133 Sn, at excitation energies exceeding the neutron separation energy by 1 MeV. The β-delayed one- and two-neutron emission branching ratios of 134 In were determined and compared with theoretical calculations. The β-delayed one-neutron decay was observed to be dominant β-decay branch of 134 In even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of 134 Sn. Transitions following the β decay of 135 In are reported for the first time, including γ rays tentatively attributed to 135 Sn. In total, six new levels were identified in 134 Sn on the basis of the βγγ coincidences observed in the 134 In and 135 Inβ decays. A transition that might be a candidate for deexciting the missing neutron single-particle 13/2 + state in 133 Sn was observed in both β decays and its assignment is discussed. Experimental level schemes of 134 Sn and 135 Sn are compared with shell-model predictions. Using the fast timing technique, half-lives of the 2 + , 4 + , and 6 + levels in 134 Sn were determined. From the lifetime of the 4 + state measured for the first time, an unexpectedly large B(E2;4 + → 2 + ) transition strength was deduced, which is not reproduced by the shell-model calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

The Spectacular Ultraviolet Flash from the Peculiar Type Ia Supernova 2019yvq

Early observations of Type Ia supernovae (SNe Ia) provide essential clues for understanding the progenitor system that gave rise to the terminal thermonuclear explosion. Here, we present exquisite observations of SN 2019yvq, the second observed SN Ia, after iPTF 14atg, to display an early flash of emission in the ultraviolet (UV) and optical. Our analysis finds that SN 2019yvq was unusual, even when ignoring the initial flash, in that it was moderately underluminous for a SN Ia ($M_g \approx -18.5$ mag at peak) yet featured very high absorption velocities ($v \approx 15,0000$ km s -1 for Si II λ6355 at peak). We find that many of the observational features of SN 2019yvq, aside from the flash, can be explained if the explosive yield of radioactive 56 Ni is relatively low (we measure $M_{^{56}\mathrm{Ni}} = 0.31 \pm 0.05\,M_\odot$) and it and other iron-group elements are concentrated in the innermost layers of the ejecta. To explain both the UV/optical flash and peak properties of SN 2019yvq we consider four different models: interaction between the SN ejecta and a nondegenerate companion, extended clumps of 56 Ni in the outer ejecta, a double-detonation explosion, and the violent merger of two white dwarfs. Each of these models has shortcomings when compared to the observations; it is clear additional tuning is required to better match SN 2019yvq. In closing, we predict that the nebular spectra of SN 2019yvq will feature either H or He emission, if the ejecta collided with a companion, strong [Ca II] emission, if it was a double detonation, or narrow [O I] emission, if it was due to a violent merger.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

It’s Dust: Solving the Mysteries of the Intrinsic Scatter and Host-galaxy Dependence of Standardized Type Ia Supernova Brightnesses

The use of Type Ia supernovae (SNe Ia) as cosmological tools has motivated significant effort to understand what drives the intrinsic scatter of SN Ia distance modulus residuals after standardization, characterize the distribution of SN Ia colors, and explain why properties of the host galaxies of the SNe correlate with SN Ia distance modulus residuals. We use a compiled sample of ~1450 spectroscopically confirmed photometric light curves of SNe Ia and propose a solution to these three problems simultaneously that also explains an empirical 11 σ detection of the dependence of Hubble residual scatter on SN Ia color. We introduce a physical model of color where intrinsic SN Ia colors with a relatively weak correlation with luminosity are combined with extrinsic dust-like colors ( E ( B - V )) with a wide range of extinction parameter values ( R V ). This model captures the observed trends of Hubble residual scatter and indicates that the dominant component of SN Ia intrinsic scatter is variation in R V . We also find that the recovered E ( B - V ) and R V distributions differ based on global host-galaxy stellar mass, and this explains the observed correlation ( γ ) between mass and Hubble residuals seen in past analyses, as well as an observed 4.5 σ dependence of γ on SN Ia color. This finding removes any need to ascribe different intrinsic luminosities to different progenitor systems. Finally, we measure biases in the equation of state of dark energy ( w ) up to |Δ w | = 0.04 by replacing previous models of SN color with our dust-based model; this bias is larger than any systematic uncertainty in previous SN Ia cosmological analyses.

Astronomy & Astrophysics↗