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At least 541 records · Page 30
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DOE OSTI2020

Materials Data on KHoF4 by Materials Project

KHoF4 crystallizes in the trigonal P3_1 space group. The structure is three-dimensional. there are six inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to eight F1- atoms to form distorted KF8 hexagonal bipyramids that share a cornercorner with one HoF7 pentagonal bipyramid, edges with two KF8 hexagonal bipyramids, and edges with six HoF7 pentagonal bipyramids. There are a spread of K–F bond distances ranging from 2.55–3.08 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of K–F bond distances ranging from 2.61–3.01 Å. In the third K1+ site, K1+ is bonded to eight F1- atoms to form distorted KF8 hexagonal bipyramids that share a cornercorner with one HoF7 pentagonal bipyramid, edges with two KF8 hexagonal bipyramids, and edges with six HoF7 pentagonal bipyramids. There are a spread of K–F bond distances ranging from 2.61–3.03 Å. In the fourth K1+ site, K1+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of K–F bond distances ranging from 2.59–3.06 Å. In the fifth K1+ site, K1+ is bonded to eight F1- atoms to form distorted KF8 hexagonal bipyramids that share a cornercorner with one HoF7 pentagonal bipyramid, edges with two KF8 hexagonal bipyramids, and edges with six HoF7 pentagonal bipyramids. There are a spread of K–F bond distances ranging from 2.62–3.09 Å. In the sixth K1+ site, K1+ is bonded in a distorted body-centered cubic geometry to eight F1- atoms. There are a spread of K–F bond distances ranging from 2.60–2.90 Å. There are six inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to seven F1- atoms to form HoF7 pentagonal bipyramids that share a cornercorner with one KF8 hexagonal bipyramid, corners with three equivalent HoF7 pentagonal bipyramids, edges with three KF8 hexagonal bipyramids, and an edgeedge with one HoF7 pentagonal bipyramid. There are a spread of Ho–F bond distances ranging from 2.16–2.30 Å. In the second Ho3+ site, Ho3+ is bonded to seven F1- atoms to form HoF7 pentagonal bipyramids that share corners with five HoF7 pentagonal bipyramids, edges with three KF8 hexagonal bipyramids, and an edgeedge with one HoF7 pentagonal bipyramid. There are a spread of Ho–F bond distances ranging from 2.21–2.28 Å. In the third Ho3+ site, Ho3+ is bonded to seven F1- atoms to form HoF7 pentagonal bipyramids that share a cornercorner with one KF8 hexagonal bipyramid, corners with three equivalent HoF7 pentagonal bipyramids, edges with three KF8 hexagonal bipyramids, and an edgeedge with one HoF7 pentagonal bipyramid. There are a spread of Ho–F bond distances ranging from 2.16–2.29 Å. In the fourth Ho3+ site, Ho3+ is bonded to seven F1- atoms to form HoF7 pentagonal bipyramids that share corners with five HoF7 pentagonal bipyramids, edges with three KF8 hexagonal bipyramids, and an edgeedge with one HoF7 pentagonal bipyramid. There are a spread of Ho–F bond distances ranging from 2.21–2.28 Å. In the fifth Ho3+ site, Ho3+ is bonded to seven F1- atoms to form HoF7 pentagonal bipyramids that share a cornercorner with one KF8 hexagonal bipyramid, corners with three equivalent HoF7 pentagonal bipyramids, edges with three KF8 hexagonal bipyramids, and an edgeedge with one HoF7 pentagonal bipyramid. There are a spread of Ho–F bond distances ranging from 2.16–2.29 Å. In the sixth Ho3+ site, Ho3+ is bonded to seven F1- atoms to form HoF7 pentagonal bipyramids that share corners with five HoF7 pentagonal bipyramids, edges with three KF8 hexagonal bipyramids, and an edgeedge with one HoF7 pentagonal bipyramid. There are a spread of Ho–F bond distances ranging from 2.21–2.28 Å. There are twenty-four inequivalent F1- sites. In the first F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the second F1- site, F1- is bonded in a 2-coordinate geometry to two K1+ and two Ho3+ atoms. In the third F1- site, F1- is bonded in a 3-coordinate geometry to one K1+ and two equivalent Ho3+ atoms. In the fourth F1- site, F1- is bonded in a 2-coordinate geometry to one K1+ and two Ho3+ atoms. In the fifth F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the sixth F1- site, F1- is bonded in a 2-coordinate geometry to two K1+ and two Ho3+ atoms. In the seventh F1- site, F1- is bonded in a 2-coordinate geometry to one K1+ and two Ho3+ atoms. In the eighth F1- site, F1- is bonded in a 2-coordinate geometry to one K1+ and two equivalent Ho3+ atoms. In the ninth F1- site, F1- is bonded in a 2-coordinate geometry to two K1+ and two Ho3+ atoms. In the tenth F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the eleventh F1- site, F1- is bonded in a 3-coordinate geometry to one K1+ and two equivalent Ho3+ atoms. In the twelfth F1- site, F1- is bonded in a 2-coordinate geometry to one K1+ and two Ho3+ atoms. In the thirteenth F1- site, F1- is bonded to three K1+ and one Ho3+ atom to form a mixture of corner and edge-sharing FK3Ho tetrahedra. In the fourteenth F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the fifteenth F1- site, F1- is bonded to three K1+ and one Ho3+ atom to form a mixture of distorted corner and edge-sharing FK3Ho tetrahedra. In the sixteenth F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the seventeenth F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the eighteenth F1- site, F1- is bonded to three K1+ and one Ho3+ atom to form a mixture of distorted corner and edge-sharing FK3Ho tetrahedra. In the nineteenth F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the twentieth F1- site, F1- is bonded to three K1+ and one Ho3+ atom to form a mixture of distorted corner and edge-sharing FK3Ho tetrahedra. In the twenty-first F1- site, F1- is bonded to three K1+ and one Ho3+ atom to form a mixture of distorted corner and edge-sharing FK3Ho tetrahedra. In the twenty-second F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the twenty-third F1- site, F1- is bonded in a 4-coordinate geometry to two K1+ and two Ho3+ atoms. In the twenty-fourth F1- site, F1- is bonded to three K1+ and one Ho3+ atom to form a mixture of distorted corner and edge-sharing FK3Ho tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(Ni2B)6 by Materials Project

Ho(Ni2B)6 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Ho3+ is bonded in a distorted hexagonal planar geometry to six B3- atoms. There are a spread of Ho–B bond distances ranging from 2.96–3.29 Å. There are seven inequivalent Ni+1.25+ sites. In the first Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of edge and corner-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 1.98–2.09 Å. In the second Ni+1.25+ site, Ni+1.25+ is bonded in a 3-coordinate geometry to four B3- atoms. There are a spread of Ni–B bond distances ranging from 2.10–2.57 Å. In the third Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of distorted edge and corner-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 2.02–2.10 Å. In the fourth Ni+1.25+ site, Ni+1.25+ is bonded in a T-shaped geometry to three B3- atoms. There are two shorter (2.00 Å) and one longer (2.09 Å) Ni–B bond lengths. In the fifth Ni+1.25+ site, Ni+1.25+ is bonded in a distorted T-shaped geometry to three B3- atoms. There are one shorter (2.05 Å) and two longer (2.13 Å) Ni–B bond lengths. In the sixth Ni+1.25+ site, Ni+1.25+ is bonded in a T-shaped geometry to three B3- atoms. There are a spread of Ni–B bond distances ranging from 2.03–2.10 Å. In the seventh Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of edge and corner-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 2.01–2.08 Å. There are four inequivalent B3- sites. In the first B3- site, B3- is bonded in a 7-coordinate geometry to one Ho3+ and seven Ni+1.25+ atoms. In the second B3- site, B3- is bonded in a 7-coordinate geometry to one Ho3+ and seven Ni+1.25+ atoms. In the third B3- site, B3- is bonded in a 7-coordinate geometry to one Ho3+ and seven Ni+1.25+ atoms. In the fourth B3- site, B3- is bonded in a 9-coordinate geometry to one Ho3+ and eight Ni+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2HoCu3(PbO4)2 by Materials Project

Pb2Sr2HoCu3O8 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.60–2.83 Å. Ho3+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Ho–O bond lengths are 2.40 Å. There are two inequivalent Cu+1.67+ sites. In the first Cu+1.67+ site, Cu+1.67+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.86 Å. In the second Cu+1.67+ site, Cu+1.67+ is bonded to five O2- atoms to form CuO5 square pyramids that share a cornercorner with one PbO5 square pyramid and corners with four equivalent CuO5 square pyramids. There are four shorter (1.93 Å) and one longer (2.36 Å) Cu–O bond lengths. Pb2+ is bonded to five O2- atoms to form PbO5 square pyramids that share a cornercorner with one CuO5 square pyramid, corners with four equivalent PbO5 square pyramids, and edges with four equivalent PbO5 square pyramids. There are one shorter (2.19 Å) and four longer (2.71 Å) Pb–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to two equivalent Sr2+, two equivalent Ho3+, and two equivalent Cu+1.67+ atoms. In the second O2- site, O2- is bonded to one Sr2+, one Cu+1.67+, and four equivalent Pb2+ atoms to form a mixture of distorted edge and corner-sharing OSrCuPb4 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the third O2- site, O2- is bonded to four equivalent Sr2+, one Cu+1.67+, and one Pb2+ atom to form distorted OSr4CuPb octahedra that share corners with four equivalent OSr4CuPb octahedra and edges with eight OSrCuPb4 octahedra. The corner-sharing octahedral tilt angles are 20°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2HoPCO7 by Materials Project

Li2HoCPO7 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 1.95–2.62 Å. Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.20–2.54 Å. C4+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of C–O bond distances ranging from 1.27–1.32 Å. P5+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of P–O bond distances ranging from 1.54–1.58 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Li1+ and one C4+ atom. In the second O2- site, O2- is bonded to two equivalent Li1+, one Ho3+, and one C4+ atom to form distorted edge-sharing OLi2HoC trigonal pyramids. In the third O2- site, O2- is bonded to two equivalent Li1+, one Ho3+, and one C4+ atom to form distorted edge-sharing OLi2HoC trigonal pyramids. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Ho3+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Li1+, two equivalent Ho3+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Li1+, one Ho3+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Thermal evolution of spin excitations in honeycomb Ising antiferromagnetic FePSe 3

We use elastic and inelastic neutron scattering (INS) to study the antiferromagnetic (AF) phase transitions and spin excitations in the two-dimensional (2D) zig-zag antiferromagnet FePSe 3 . By determining the magnetic order parameter across the AF phase transition, we conclude that the AF phase transition in FePSe 3 is first-order in nature. In addition, our INS measurements reveal that the spin waves in the AF ordered state have a large easy-axis magnetic anisotropy gap, consistent with an Ising Hamiltonian, and possible biquadratic magnetic exchange interactions. On warming across T N , we find that dispersive spin excitations associated with three-fold rotational symmetric AF fluctuations change into FM spin fluctuations above T N . These results suggest that the first-order AF phase transition in FePSe 3 may arise from the competition between C 3 symmetric AF and C 1 symmetric FM spin fluctuations around T N , in place of a conventional second-order AF phase transition.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Surface plasmon driven near- and midinfrared photoconductivity in ligand-free ITO nanocrystal films

Semiconductor nanocrystals (NCs) offer exciting opportunities to deploy infrared optoelectronic technology in a variety of applications that are off-limits to conventional single-crystalline materials. However, the performance and stability of state-of-the-art NC-based devices strongly depend on the details of the NC surface and its passivating ligands. Here, the authors use indium tin oxide NC films stripped of organic ligands and conformally coated with Al 2 O 3 to show that absorption enabled by infrared localized surface plasmon resonances permit infrared photoconduction. For Au electrodes, these metallic NC films exhibit stable photoconductive performance over months in ambient and under electrical stress.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Astrometric Microlensing by Primordial Black Holes with the Roman Space Telescope

Abstract Primordial black holes (PBHs) could explain some fraction of dark matter and shed light on many areas of early-Universe physics. Despite over half a century of research interest, a PBH population has so far eluded detection. The most competitive constraints on the fraction of dark matter comprised of PBHs ( f DM ) in the (10 −9 –10) M ⊙ mass ranges come from photometric microlensing and bound f DM ≲ 10 −2 –10 −1 . With the advent of the Roman Space Telescope with its submilliarcsecond astrometric capabilities and its planned Galactic Bulge Time Domain Survey (GBTDS), detecting astrometric microlensing signatures will become routine. Compared with photometric microlensing, astrometric microlensing signals are sensitive to different lens masses–distance configurations and contain different information, making it a complimentary lensing probe. At submilliarcsecond astrometric precision, astrometric microlensing signals are typically detectable at larger lens–source separations than photometric signals, suggesting a microlensing detection channel of pure astrometric events. We use a Galactic simulation to predict the number of detectable microlensing events during the GBTDS via this pure astrometric microlensing channel. Assuming an absolute astrometric precision floor for bright stars of 0.1 mas for the GBTDS, we find that the number of detectable events peaks at ≈10 3 f DM for a population of 1 M ⊙ PBHs and tapers to ≈10 f DM and ≈100 f DM at 10 −4 M ⊙ and 10 3 M ⊙ , respectively. Accounting for the distinguishability of PBHs from stellar lenses, we conclude the GBTDS will be sensitive to a PBH population at f DM down to ≈10 −1 –10 −3 for (10 −1 –10 2 ) M ⊙ likely yielding novel PBH constraints.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Materials Data on HoMg(BO2)5 by Materials Project

MgHo(BO2)5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 2.08–2.37 Å. Ho3+ is bonded in a 9-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.98 Å. There are five inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.49 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. In the third B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.37 Å) and one longer (1.38 Å) B–O bond length. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.51 Å. In the fifth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Ho3+, and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mg2+, one Ho3+, and two B3+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Mg2+, one Ho3+, and one B3+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ho3+ and one B3+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2ReB6 by Materials Project

Ho2ReB6 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 4-coordinate geometry to fourteen B2- atoms. There are a spread of Ho–B bond distances ranging from 2.74–2.83 Å. In the second Ho3+ site, Ho3+ is bonded to twelve B2- atoms to form a mixture of edge and face-sharing HoB12 cuboctahedra. There are a spread of Ho–B bond distances ranging from 2.59–2.62 Å. Re6+ is bonded in a 10-coordinate geometry to ten B2- atoms. There are a spread of Re–B bond distances ranging from 2.36–2.41 Å. There are six inequivalent B2- sites. In the first B2- site, B2- is bonded in a 9-coordinate geometry to six Ho3+ and three B2- atoms. There are a spread of B–B bond distances ranging from 1.84–1.95 Å. In the second B2- site, B2- is bonded in a 3-coordinate geometry to four equivalent Ho3+, two equivalent Re6+, and three B2- atoms. There are a spread of B–B bond distances ranging from 1.80–1.83 Å. In the third B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. The B–B bond length is 1.81 Å. In the fourth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. There is one shorter (1.74 Å) and one longer (1.85 Å) B–B bond length. In the fifth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. The B–B bond length is 1.80 Å. In the sixth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2HoPCO7 by Materials Project

Na2HoCPO7 crystallizes in the monoclinic P2_1/m 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 2.23–2.69 Å. Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.23–2.35 Å. C4+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of C–O bond distances ranging from 1.26–1.33 Å. P5+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of P–O bond distances ranging from 1.55–1.58 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Na1+ and one C4+ atom. In the second O2- site, O2- is bonded to two equivalent Na1+, one Ho3+, and one C4+ atom to form distorted ONa2HoC trigonal pyramids that share corners with three equivalent ONa2HoP tetrahedra and edges with two equivalent ONa2HoC trigonal pyramids. In the third O2- site, O2- is bonded to two equivalent Na1+, one Ho3+, and one C4+ atom to form distorted ONa2HoC trigonal pyramids that share corners with three equivalent ONa2HoP tetrahedra and edges with two equivalent ONa2HoC trigonal pyramids. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ho3+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Ho3+, and one P5+ atom. In the sixth O2- site, O2- is bonded to two equivalent Na1+, one Ho3+, and one P5+ atom to form distorted corner-sharing ONa2HoP tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Kinetics and Mechanism of the Singlet Oxygen Atom Reaction with Dimethyl Ether

Here, we combine in situ laser spectroscopy, quantum chemistry, and kinetic calculations to study the reaction of a singlet oxygen atom with dimethyl ether. Infrared laser absorption spectroscopy and Faraday rotation spectroscopy are used for the detection and quantification of the reaction products OH, H 2 O, HO 2 , and CH 2 O on submillisecond time scales. Fitting temporal profiles of products with simulations using an in-house reaction mechanism allows product branching to be quantified at 30, 60, and 150 Torr. The experimentally determined product branching agrees well with master equation calculations based on electronic structure data and transition state theory. The calculations demonstrate that the dimethyl peroxide (CH 3 OOCH 3 ) generated via O-insertion into the C–O bond undergoes subsequent dissociation to CH 3 O + CH 3 O through energetically favored reactions without an intrinsic barrier. This O-insertion mechanism can be important for understanding the fate of biofuels leaking into the atmosphere and for plasma-based biofuel processing technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Extraction and Separation of Rare-Earth Elements from Coal Fly Ash and Leachate using a Recyclable Ionic Liquid

Coal fly ash (CFA) can be a promising source for recovering rare-earth elements (REEs), as it contains a broad range of REEs with average concentrations frequently exceeding those in traditional rare earth mines. Recent research from our group has demonstrated that REEs can be preferentially extracted from CFA solids using a recyclable ionic liquid (IL), betainium bis-(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]). When CFA was heated with the mixture of IL and an aqueous solution above 65°C, most leached REEs partitioned into the IL phase and were separated from the bulk elements. Subsequent acid stripping of the REE-loaded IL removed the REEs and regenerated the IL for reuse in multiple extraction cycles. This IL-based REE-CFA recovery method has been applied to ten CFA samples derived from different coal sources, including ash recovered from disposal ponds. Analysis of 34 elements confirmed the process consistently achieved high REE recovery efficiency, with strong selectivity over bulk and trace elements across diverse CFA types. In addition to the IL-solid extraction, the performance of [Hbet][Tf2N] in extracting REEs from fly-ash leachates have been evaluated by four commonly used leaching reagents, including HCl, HNO3, H2SO4, and citrate. During the IL-leachate extraction, [Hbet][Tf2N] was mixed and heated with a Class C fly ash leachate generated from each leaching reagent, followed by an acid stripping. It was observed that the partitioning and recovery of REEs increased as the leachate pH increased from 3 to 11. Among the investigated leachates, HCl and citrate proved to be the most compatible with IL extraction, exhibiting a slightly higher REE recovery and a lower non-REE co-extraction compared to the IL-solid extraction. Sc, Y, Nd, Sm, Gd, Dy, and Yb consistently showed a high recovery rate from both CFA solids and leachates. Notably, Pr, Tb, and Ho, which were not previously leached from the CFA solids, were partially recovered from the leachates. Overall, our studies revealed the strong potential of [Hbet][Tf2N] for effectively recovering REEs from leachates, highlighting its applicability as a sustainable strategy for other aqueous REE feedstocks. Furthermore, a techno-economic analysis will be performed to quantify the economic viability of the IL-based REE recovery method and guide future process improvement.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on Na2HoNb5O15 by Materials Project

Na2HoNb5O15 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are two shorter (2.69 Å) and four longer (2.93 Å) Na–O bond lengths. Ho3+ is bonded to twelve O2- atoms to form HoO12 cuboctahedra that share faces with two equivalent HoO12 cuboctahedra and faces with eight equivalent NbO6 octahedra. There are four shorter (2.58 Å) and eight longer (2.66 Å) Ho–O bond lengths. There are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 0–33°. There is two shorter (1.97 Å) and four longer (2.01 Å) Nb–O bond length. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra and faces with two equivalent HoO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 13–43°. There are a spread of Nb–O bond distances ranging from 1.92–2.08 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Na1+ and two Nb5+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+ and two equivalent Nb5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Nb5+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two equivalent Nb5+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ho3+ and two equivalent Nb5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Inverse-Designed Photonics for Semiconductor Foundries

Silicon photonics is becoming a leading technology in photonics, displacing traditional fiber optic transceivers and enabling new applications. Further improving the density and performance of silicon photonics, however, has been challenging due to the large size and limited performance of traditional semianalytically designed components. Automated optimization of photonic devices using inverse design is a promising path forward but has, until now, faced difficulties in producing designs that can be fabricated reliably at scale. In this paper we experimentally demonstrate four inverse-designed devices made successfully in a commercial silicon photonics foundry: a spatial mode multiplexer, wavelength demultiplexer, 50–50 directional coupler, and 3-way power splitter. These devices are efficient, robust to fabrication variability, and compact, with footprints only a few micrometers across. They pave the way forward for the widespread practical use of inverse design.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2Co12P7 by Materials Project

Ho2Co12P7 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to six equivalent P3- atoms to form distorted HoP6 pentagonal pyramids that share corners with twelve CoP4 tetrahedra, corners with six equivalent CoP5 trigonal bipyramids, edges with nine CoP4 tetrahedra, edges with three equivalent CoP5 trigonal bipyramids, and faces with two equivalent HoP6 pentagonal pyramids. All Ho–P bond lengths are 2.82 Å. In the second Ho3+ site, Ho3+ is bonded to six equivalent P3- atoms to form distorted HoP6 pentagonal pyramids that share corners with twelve CoP4 tetrahedra, corners with six equivalent CoP5 trigonal bipyramids, edges with twelve CoP4 tetrahedra, and faces with two equivalent HoP6 pentagonal pyramids. All Ho–P bond lengths are 2.85 Å. There are four inequivalent Co+1.25+ sites. In the first Co+1.25+ site, Co+1.25+ is bonded to four P3- atoms to form CoP4 tetrahedra that share corners with four HoP6 pentagonal pyramids, corners with ten CoP4 tetrahedra, corners with two equivalent CoP5 trigonal bipyramids, an edgeedge with one HoP6 pentagonal pyramid, edges with three CoP4 tetrahedra, and edges with four equivalent CoP5 trigonal bipyramids. There are a spread of Co–P bond distances ranging from 2.13–2.27 Å. In the second Co+1.25+ site, Co+1.25+ is bonded to four P3- atoms to form CoP4 tetrahedra that share corners with two equivalent HoP6 pentagonal pyramids, corners with ten CoP4 tetrahedra, corners with four equivalent CoP5 trigonal bipyramids, edges with three HoP6 pentagonal pyramids, edges with four CoP4 tetrahedra, and an edgeedge with one CoP5 trigonal bipyramid. There are a spread of Co–P bond distances ranging from 2.24–2.31 Å. In the third Co+1.25+ site, Co+1.25+ is bonded to five P3- atoms to form distorted CoP5 trigonal bipyramids that share corners with four HoP6 pentagonal pyramids, corners with eight CoP4 tetrahedra, corners with four equivalent CoP5 trigonal bipyramids, an edgeedge with one HoP6 pentagonal pyramid, edges with seven CoP4 tetrahedra, and edges with four equivalent CoP5 trigonal bipyramids. There are a spread of Co–P bond distances ranging from 2.23–2.56 Å. In the fourth Co+1.25+ site, Co+1.25+ is bonded to four P3- atoms to form CoP4 tetrahedra that share corners with two equivalent HoP6 pentagonal pyramids, corners with twelve CoP4 tetrahedra, corners with two equivalent CoP5 trigonal bipyramids, edges with three HoP6 pentagonal pyramids, edges with three CoP4 tetrahedra, and edges with two equivalent CoP5 trigonal bipyramids. There are a spread of Co–P bond distances ranging from 2.24–2.29 Å. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a 3-coordinate geometry to nine Co+1.25+ atoms. In the second P3- site, P3- is bonded in a 9-coordinate geometry to two equivalent Ho3+ and seven Co+1.25+ atoms. In the third P3- site, P3- is bonded in a 9-coordinate geometry to two equivalent Ho3+ and seven Co+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Multiple Tunable Hyperbolic Resonances in Broadband Infrared Carbon-Nanotube Metamaterials

Aligned densely packed carbon-nanotube metamaterials prepared using vacuum filtration are an emerging infrared nanophotonic material. We report multiple hyperbolic plasmon resonances, together spanning the mid-infrared, in individual resonators made from aligned and densely packed carbon nanotubes. In a near-field scanning optical microscopy (NSOM) imaging study of nanotube metamaterial resonators, we observe distinct deeply subwavelength field profiles at the fundamental and higher-order resonant frequencies. The wafer-scale area of the nanotube metamaterials allows us to combine this near-field imaging with a systematic far-field spectroscopic study of the scaling properties of many resonator arrays. Thorough theoretical modeling agrees with these measurements and identifies the resonances as higher-order Fabry-Perot (FP) resonances of hyperbolic waveguide modes. Nanotube resonator arrays show broadband extinction from 1.5–10 µm and reversibly switchable extinction in the 3–5 µm atmospheric transparency window through the coexistence of multiple modes in individual ribbons. Broadband carbon-nanotube metamaterials supporting multiple resonant modes are a promising candidate for ultracompact absorbers, tunable thermal emitters, and broadband sensors in the mid-infrared.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KHo2Cu(MoO4)4 by Materials Project

KHo2Cu(MoO4)4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.69–3.23 Å. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.27–2.49 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.78–1.87 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.77–1.88 Å. Cu1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cu–O bond distances ranging from 2.05–2.66 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Mo6+, and one Cu1+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Mo6+, and one Cu1+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Mo6+, and one Cu1+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Ho3+, and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+, one Ho3+, and one Mo6+ atom.

36 MATERIALS SCIENCE↗