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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Lu(PO3)3 by Materials Project

Lu(PO3)3 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. Lu3+ is bonded to six O2- atoms to form LuO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Lu–O bond distances ranging from 2.17–2.21 Å. There are three inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent LuO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 23–26°. There are a spread of P–O bond distances ranging from 1.49–1.61 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent LuO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent LuO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–34°. There is two shorter (1.50 Å) and two longer (1.60 Å) P–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Lu3+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Lu3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Lu3+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Lu3+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Lu3+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Lu3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(CuO2)2 by Materials Project

Lu(CuO2)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Lu3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Lu–O bond distances ranging from 2.31–2.34 Å. There are two inequivalent Cu+2.50+ sites. In the first Cu+2.50+ site, Cu+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.89 Å) and two longer (1.92 Å) Cu–O bond length. In the second Cu+2.50+ site, Cu+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.89 Å) and two longer (1.91 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Lu3+ and two Cu+2.50+ atoms to form a mixture of distorted edge and corner-sharing OLu2Cu2 tetrahedra. In the second O2- site, O2- is bonded to two equivalent Lu3+ and two Cu+2.50+ atoms to form a mixture of distorted edge and corner-sharing OLu2Cu2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(HO)3 by Materials Project

Lu(OH)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Lu3+ is bonded in a 9-coordinate geometry to nine equivalent O2- atoms. There are six shorter (2.36 Å) and three longer (2.43 Å) Lu–O bond lengths. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. O2- is bonded in a single-bond geometry to three equivalent Lu3+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(AlC)3 by Materials Project

Lu(AlC)3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Lu3+ is bonded to six equivalent C4- atoms to form LuC6 octahedra that share corners with six equivalent AlC4 tetrahedra, edges with six equivalent LuC6 octahedra, and edges with six equivalent AlC4 tetrahedra. All Lu–C bond lengths are 2.50 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent LuC6 octahedra, corners with seven equivalent AlC4 tetrahedra, and edges with three equivalent LuC6 octahedra. The corner-sharing octahedral tilt angles are 18°. There are one shorter (2.02 Å) and three longer (2.09 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded in a trigonal planar geometry to three equivalent C4- atoms. All Al–C bond lengths are 1.97 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded to three equivalent Lu3+ and three equivalent Al3+ atoms to form distorted CLu3Al3 octahedra that share corners with three equivalent CLu3Al3 octahedra, corners with three equivalent CAl5 trigonal bipyramids, and edges with nine equivalent CLu3Al3 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second C4- site, C4- is bonded to five Al3+ atoms to form CAl5 trigonal bipyramids that share corners with six equivalent CLu3Al3 octahedra and corners with six equivalent CAl5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 70°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(FeO2)2 by Materials Project

LuFe2O4 is Aluminum carbonitride-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Lu3+ sites. In the first Lu3+ site, Lu3+ is bonded to six O2- atoms to form distorted LuO6 octahedra that share corners with six FeO5 trigonal bipyramids and edges with six equivalent LuO6 octahedra. There are a spread of Lu–O bond distances ranging from 2.22–2.28 Å. In the second Lu3+ site, Lu3+ is bonded to six O2- atoms to form LuO6 octahedra that share corners with six FeO5 trigonal bipyramids and edges with six LuO6 octahedra. There are a spread of Lu–O bond distances ranging from 2.22–2.27 Å. There are four inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 61–70°. There are a spread of Fe–O bond distances ranging from 1.98–2.12 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six equivalent FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 57–66°. There are one shorter (1.98 Å) and four longer (2.13 Å) Fe–O bond lengths. In the third Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six equivalent FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 61–70°. There are a spread of Fe–O bond distances ranging from 2.02–2.28 Å. In the fourth Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 57–65°. There are a spread of Fe–O bond distances ranging from 1.96–2.21 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded to four Fe+2.50+ atoms to form OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six equivalent OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the second O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra. In the third O2- site, O2- is bonded to four Fe+2.50+ atoms to form distorted OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six equivalent OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the fourth O2- site, O2- is bonded to four Fe+2.50+ atoms to form OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the fifth O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form distorted OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra. In the sixth O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra. In the seventh O2- site, O2- is bonded to four Fe+2.50+ atoms to form OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the eighth O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(FeO2)2 by Materials Project

LuFe2O4 is Aluminum carbonitride-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Lu3+ sites. In the first Lu3+ site, Lu3+ is bonded to six O2- atoms to form distorted LuO6 octahedra that share corners with six FeO5 trigonal bipyramids and edges with six equivalent LuO6 octahedra. There are a spread of Lu–O bond distances ranging from 2.24–2.27 Å. In the second Lu3+ site, Lu3+ is bonded to six O2- atoms to form LuO6 octahedra that share corners with six FeO5 trigonal bipyramids and edges with six LuO6 octahedra. There are a spread of Lu–O bond distances ranging from 2.23–2.27 Å. There are four inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six equivalent FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 61–67°. There are a spread of Fe–O bond distances ranging from 1.94–2.24 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 60–65°. There are a spread of Fe–O bond distances ranging from 2.01–2.19 Å. In the third Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 62–66°. There are a spread of Fe–O bond distances ranging from 1.99–2.15 Å. In the fourth Fe+2.50+ site, Fe+2.50+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with three LuO6 octahedra, corners with six equivalent FeO5 trigonal bipyramids, and edges with three FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 61–64°. There are a spread of Fe–O bond distances ranging from 1.94–2.17 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded to four Fe+2.50+ atoms to form OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six equivalent OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the second O2- site, O2- is bonded to four Fe+2.50+ atoms to form OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six equivalent OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the third O2- site, O2- is bonded to four Fe+2.50+ atoms to form OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the fourth O2- site, O2- is bonded to four Fe+2.50+ atoms to form OFe4 trigonal pyramids that share corners with four OLu3Fe tetrahedra, corners with six OFe4 trigonal pyramids, and edges with three OFe4 trigonal pyramids. In the fifth O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra. In the sixth O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra. In the seventh O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra. In the eighth O2- site, O2- is bonded to three Lu3+ and one Fe+2.50+ atom to form OLu3Fe tetrahedra that share corners with nine OLu3Fe tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three OLu3Fe tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(PO3)3 by Materials Project

Lu(PO3)3 crystallizes in the cubic I-43d space group. The structure is three-dimensional. Lu3+ is bonded to six O2- atoms to form LuO6 octahedra that share corners with six equivalent PO4 tetrahedra. There are three shorter (2.18 Å) and three longer (2.19 Å) Lu–O bond lengths. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent LuO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–32°. There are a spread of P–O bond distances ranging from 1.49–1.61 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent P5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Lu3+ and one P5+ atom. In the third O2- site, O2- is bonded in a distorted linear geometry to one Lu3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(CuS)3 by Materials Project

Lu(CuS)3 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Lu3+ is bonded to six equivalent S2- atoms to form LuS6 octahedra that share corners with twelve equivalent CuS4 tetrahedra, edges with three equivalent LuS6 octahedra, and edges with six equivalent CuS4 tetrahedra. All Lu–S bond lengths are 2.69 Å. Cu1+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with four equivalent LuS6 octahedra, corners with six equivalent CuS4 tetrahedra, edges with two equivalent LuS6 octahedra, and edges with three equivalent CuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–56°. There are a spread of Cu–S bond distances ranging from 2.33–2.41 Å. S2- is bonded to two equivalent Lu3+ and four equivalent Cu1+ atoms to form a mixture of distorted corner and edge-sharing SLu2Cu4 octahedra. The corner-sharing octahedra tilt angles range from 0–90°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(Mo3Se4)2 by Materials Project

Lu(Mo3Se4)2 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Lu3+ is bonded in a body-centered cubic geometry to eight Se2- atoms. There are two shorter (2.76 Å) and six longer (3.09 Å) Lu–Se bond lengths. Mo+2.17+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.54–2.74 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to one Lu3+ and three equivalent Mo+2.17+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Lu3+ and four equivalent Mo+2.17+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A 9.2-GHz clock transition in a Lu(II) molecular spin qubit arising from a 3,467-MHz hyperfine interaction

Spins in molecules are particularly attractive targets for next-generation quantum technologies, enabling chemically programmable qubits and potential for scale-up via self-assembly. Here, we report observation of one of the largest hyperfine interactions for a molecular system, A iso = 3467±50 MHz, along with an associated clock transition of unprecedented magnitude. This is achieved through chemical control of the degree of s-orbital mixing into the spin-bearing d-orbital associated with a series of spin-½ La(II) and Lu(II) complexes. Increased s-orbital character reduces spin-orbit coupling and enhances the electron-nuclear Fermi contact interaction. Both outcomes are advantageous for quantum applications: the former reduces spin-lattice relaxation, while the latter maximizes the hyperfine interaction that, in turn, generates a 9 gigahertz clock transition, leading to an increase in phase memory time from 1.0±0.4 to 12±1 microseconds for one of the Lu(II) complexes. Furthermore, these findings suggest strategies for development of molecular quantum technologies, akin to trapped ion systems.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Structural modulation and spin glassiness upon oxidation in oxygen storage material LnFeMnO 4+x for Ln = Y, Lu, and Yb

The mixed valence multiferroic LnFe 2+ Fe 3+ O 4 (where Ln = Y, Lu, and Yb) can reversibly uptake oxygen into its lattice, which is evidenced by a crystallographic phase transition along with the appearance of structural modulations. In this study, we show that the Mn-substituted version of this multiferroic can also be readily oxidized to LnFe 3+ Mn 3+ O 4.5 revealing similar oxygen storage behavior. Through neutron, electron, and synchrotron x-ray diffraction studies, we observe a structural modulation that we attribute to a displacement wave in the fully oxidized compound. This wave exhibits commensurability with a wavevector q = (-2/7, 1/7, 0). Bond valence summation analysis of plausible interstitial oxygen positions suggests that oxygen insertion likely occurs at the middle of the Fe/Mn–O bipyramid layers. The structural modulation of LnFeMnO 4.5 is two-dimensional, propagates along the ab-plane, and is highly symmetric as 12 identical modulation vectors are observed in the diffraction patterns. The nature of the lanthanide, Ln 3+ , does not seem to influence such modulations since we observe identical satellite reflections for all three samples of Ln = Y, Lu, and Yb. Both LnFeMnO 4 and LnFeMnO 4.5 display spin glassy behavior with 2D short-range magnetic ordering being observed in LnFeMnO 4 . Analysis of the neutron diffraction data reveals a correlation length of ~10 nm. Upon oxidation to LnFeMnO 4.5 , the short-range magnetic order is significantly suppressed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Persistent structural distortion for anticipated improper ferroelectricity in ultrathin h-Lu 1− x Ca x MnO 3 films

Improper ferroelectricity in hexagonal rare-earth manganites (h-RMnO 3 , R = Ho–Lu, Y, Sc) arises from a geometric distortion as the primary order parameter, resilient to depolarizing fields and promising for ultrathin ferroelectric devices. However, the substrate-induced interface clamping effect, which suppresses the geometric distortion in the sub-nanometer regime, has thus far hindered the realization of two-dimensional improper ferroelectrics. This study demonstrates that doping with calcium can enhance ferroelectric structural distortion in h-LuMnO 3 thin films. Compressively strained h-Lu 1−x Ca x MnO 3 (x = 0.1, 0.2, 0.3, 0.4, 0.5) epitaxial thin films were stabilized on sapphire substrates using an h-ScFeO 3 buffer layer. We have found that the interface clamping effect is entirely overcome when the doping concentration reaches x ⩾ 0.2, establishing a potential quasi-2D ferroelectric system with a remarkably high estimated structural transition temperature of larger than 1200 K inferred indirectly from temperature-resolved reflection high-energy electron diffraction. This finding suggests a general strain engineering strategy to enhance improper ferroelectricity in hexagonal manganites.

hexagonal manganites↗
DOE OSTI2020

X Fe 4 Ge 2 ( X = Y , Lu ) and Mn 3 Pt : Filling-enforced magnetic topological metals

Magnetism, coupled with nontrivial band topology, can bring about many interesting and exotic phenomena, so that magnetic topological materials have attracted persistent research interest. However, compared with nonmagnetic topological materials (TMs), the magnetic TMs are less studied, since their magnetic structures and topological phase transitions are usually complex and the first-principles predictions are usually sensitive on the effect of Coulomb interaction. Here we present a comprehensive investigation of XFe 4 Ge 2 (X = Y, Lu) and Mn 3 Pt, and find these materials to be filling-enforced magnetic topological metals. Our first-principles calculations show that XFe 4 Ge 2 (X = Y, Lu) host Dirac points near the Fermi level at high symmetry point S. These Dirac points are protected by $\text{P}\mathcal{T}$ symmetry ($\text{P}$ and $\mathcal{T}$ are inversion and time-reversal transformations, respectively) and a twofold screw rotation symmetry. Moreover, through breaking $\text{P}\mathcal{T}$ symmetry, the Dirac points would split into Weyl nodes. Mn 3 Pt is found to host fourfold degenerate band crossings in the whole high symmetry path of A – Z . We also utilize the GGA + U scheme to take into account the effect of Coulomb repulsion and find that the filling-enforced topological properties are naturally insensitive on U .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Czochralski growth and characterization of the multicomponent garnet (Lu 1/4 Yb 1/4 Y 1/4 Gd 1/4 ) 3 Al 5 O 12

This work demonstrates the potential for practical scalable growth of complex garnets and evaluates the implications of a multicomponent composition in the optical quality and elemental distribution of a Czochralski-grown crystal. Furthermore, our experimental approach was designed to elucidate the relation between a complex garnet composition ( Lu 1 / 4 Yb 1 / 4 Y 1 / 4 Gd 1 / 4 ) 3 Al 5 O 12 , crystal growth parameters, crystal structural, and elemental homogeneity. Our hypothesis is that combining multiple rare earths (REs) that will fractionally occupy the dodecahedral site in the aluminum garnet structure will result in a stable, single garnet compound that can be grown by the Czochralski method. Single-crystal and powder x-ray diffraction indicated a single garnet phase with an increasing unit cell volume from seed to tail. In addition, we propose that the pattern of elemental segregation will be based on the deviation of the ionic radius of each constituent RE from the average RE ionic radius of the multicomponent garnet. Electron probe microanalysis revealed that ions that are smaller than that average ( Lu 3 + and Yb 3 + ) are preferentially incorporated in the crystal, while elements that are larger than that average ( Gd 3 + ) are rejected. The ionic radius of Y 3 + is close to that average and yttrium segregation was minimal. The concentrations of the four REs are closer to stoichiometric on the tail end of the boule. Scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis reveal Gd-rich inclusions with eutectic microstructures in the tail end of the boule.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Isomeric states in the neutron-rich 𝑁 = 108 nuclei 178 Yb and 179 Lu

A multinucleon transfer reaction with a 136 Xe beam and a gold-backed 176 Yb target populated isomers in N = 108 178 Yb and 179 Lu. The single decay from the t 1/2 = 203(16) ns isomer in 178 Yb to the I π = 4 + level in the ground-state band suggests a I π = 4 − assignment, and multiquasiparticle calculations associate this state with the K π = 4 − , ν 2 (1/2[510], 9/2[624]) configuration. At least two isomers were observed in 179 Lu. One likely couples the K π = 4 − configuration found in 178 Yb to the 9/2[514] quasiproton orbital to form a K π = 17/2 + level (t 1/2 = 1.0(4) µs) which primarily decays into the rotational band based on the 9/2[514] state. A second isomer was observed to decay into this same band, but at higher energy and spin. Based on its feeding pattern, its similarity to an isomer found in 181 Ta, and a multiquasiparticle calculation, it is proposed to correspond to a K π = 29/2 − state based on the π9/2[514]ν 2 (9/2[624], 11/2[615]) configuration. As a result, an analysis of the reduced hindrance factors for negative-parity, two-quasineutron isomers in the rare-earth region is presented as well.

150 ≤ A ≤ 189↗
DOE OSTI2022

SparseLU, A Novel Algorithm and Math Library for Sparse LU Factorization

Decomposing sparse matrices into lower and upper triangular matrices (sparse LU factorization) is a key operation in many computational scientific applications. We developed SparseLU, a sparse linear algebra library that implements a new algorithm for LU factorization on general sparse matrices. The new algorithm divides the input matrix into tiles to which OpenMP tasks are created for factorization computation, where only tiles that contain nonzero elements are computed. For comparative performance analysis, we used the reference library SuperLU. Testing was performed on synthetically generated matrices which replicate the conditions of the real-world matrices. SparseLU is able to reach a mean speedup of ~29× compared to SuperLU.

Valero Lara, Pedro↗
DOE OSTI2020

Low-Energy Electron Elastic Total Cross Sections for Ho, Er, Tm, Yb, Lu, and Hf Atoms

The robust Regge-pole methodology wherein is fully embedded the essential electron-electron correlation effects and the vital core polarization interaction has been used to explore negative ion formation in the large lanthanide Ho, Er, Tm, Yb, Lu, and Hf atoms through the electron elastic total cross sections (TCSs) calculations. These TCSs are characterized generally by dramatically sharp resonances manifesting ground, metastable, and excited negative ion formation during the collisions, Ramsauer-Townsend minima, and shape resonances. The novelty and generality of the Regge-pole approach is in the extraction of the negative ion binding energies (BEs) of complex heavy systems from the calculated electron TCSs. The extracted anionic BEs from the ground state TCSs for Ho, Er, Tm, Yb, Lu, and Hf atoms are 3.51 eV, 3.53 eV, 3.36 eV, 3.49 eV, 4.09 eV and 1.68 eV, respectively. The TCSs are presented and the extracted from the ground; metastable and excited anionic states BEs are compared with the available measured and/or calculated electron affinities. We conclude with a remark on the existing inconsistencies in the meaning of the electron affinity among the various measurements and/or calculations in the investigated atoms and make a recommendation to resolve the ambiguity.

Felfli, Zineb↗
NASA NTRS1977

A block iterative LU solver for weakly coupled linear systems

A hybrid technique, called the block iterative LU solver, is proposed for solving the linear equations resulting from a finite element numerical analysis of certain fluid dynamics problems where the equations are weakly coupled between distinct sets of variables. Either the block Jacobi iterative method or the block Gauss-Seidel iterative solver is combined with LU decomposition.

Cooke, C. H.↗