Search NASA⌕ Search

SEARCH · Search NASA

Results for “5”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Mechanism and kinetics of the oxidation of 1,3-butadien-1-yl (n-C 4 H 5 ): a theoretical study

Here, ab initio CCSD(T)-F12/cc-pVTZ-f12//B3LYP/6-311G(d,p) calculations of the C 4 H 5 O 2 potential energy surface have been combined with Rice–Ramsperger–Kassel–Marcus Master Equation (RRKM-ME) calculations of temperature- and pressure-dependent rate constants and product branching ratios to unravel the mechanism and kinetics of the n-C 4 H 5 + O 2 reaction. The results indicate that the reaction is fast, with the total rate constant being in the range of 3.4–5.6 × 10 –11 cm 3 molecule –1 s –1 . The main products include 1-oxo-n-butadienyl + O and acrolein + HCO, with their cumulative yield exceeding 90% at temperatures above 1500 K. Two conformers of 1-oxo-n-butadienyl + O are formed via a simple mechanism of O 2 addition to the radical site of n-C 4 H 5 followed by the cleavage of the O–O bond proceeding via a van der Waals C 4 H 5 O∙∙∙O complex. Alternatively, the pathways leading to acrolein + HCO involve significant reorganization of the heavy-atom skeleton either via formal migration of one O atom to the opposite end of the molecule or its insertion into the C1–C2 bond. Not counting thermal stabilization of the initial peroxy adducts, which prevails at low temperatures and high pressures, all other products share a minor yield of under 5%. Rate constants for the significant reaction channels have been fitted to modified Arrhenius expressions and are proposed for kinetic modeling of the oxidation of aromatic molecules and 1,3-butadiene. As a secondary reaction, n-C 4 H 5 + O 2 can be a source for the formation of acrolein observed experimentally in oxidation of the phenyl radical at low combustion temperatures, whereas another significant (secondary) product of the C 6 H 5 + O 2 reaction, furan, could be formed through unimolecular decomposition of 1-oxo-n-butadienyl. Both the n-C 4 H 5 + O 2 reaction and unimolecular decomposition of its 1-oxo-n-butadienyl primary product are shown not to be a substantial source of ketene.

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

Crystal structure of silver pentazolates AgN 5 and AgN 6

Silver pentazolate, a high energy density compound containing the cyclo-N 5 – anion, has recently been synthesized under ambient conditions. However, due to high sensitivity to irradiation, its crystal structure has not been determined. In this work, silver–nitrogen crystalline compounds under ambient conditions and at high pressures, up to 100 GPa, are predicted and characterized by performing first-principles evolutionary crystal structure searching with variable stoichiometry. It is found that newly discovered AgN 5 and AgN 6 are the only thermodynamically stable silver–nitrogen compounds at pressures between 42 and 80 GPa. In contrast to AgN 5 , the pentazolate AgN 6 compound contains N 2 diatomic molecules in addition to cyclo-N 5 – . These AgN 5 and AgN 6 crystals are metastable under ambient conditions with positive formation enthalpies of 54.95 kJ mol –1 and 46.24 kJ mol –1 , respectively. Here, the underlying cause of the stability of cyclo-N 5 – silver pentazolates is the enhanced aromaticity enabled by the charge transfer from silver atoms to nitrogen rings. To aid in the experimental identification of these materials, calculated Raman spectra are reported at ambient pressure: the frequencies of N 5 – vibrational modes of AgN 5 are in good agreement with those measured in the experiment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

First-principles investigation of elastic, vibrational, and thermodynamic properties of kagome metals CsM 3 Te 5 (M = Ti, Zr, Hf)

Kagome metals are a unique class of quantum materials characterized by their distinct atomic lattice arrangement, featuring interlocking triangles and expansive hexagonal voids. These lattice structures impart exotic properties, including superconductivity, interaction-driven topological many-body phenomena, and magnetism, among others. The kagome metal CsM 3 ⁢Te 5 (where M = Ti, Zr, or Hf) exhibits both superconductivity and nontrivial topological electronic properties, offering a promising platform for exploring topological superconductivity. This study employs first-principles density functional theory calculations to systematically analyze the elastic, mechanical, vibrational, thermodynamic, and electronic properties of CsM 3 ⁢Te 5 (M = Ti, Zr, Hf). Our calculations reveal that the studied compounds—CsTi 3 ⁢Te 5 , CsZr 3 ⁢Te 5 , and CsHf 3 ⁢Te 5 —are ductile metals with elastic properties akin to the hexagonal Bi and Sb, with average elastic constants, including a bulk modulus of 27 GPa, a shear modulus of 11 GPa, and Young's modulus of 29 GPa. We observe peculiar dispersionless, flat, phonon branches in the vibrational spectra of these metals. Additionally, we thoroughly analyze the symmetries of the zone-center phonon eigenvectors and predict vibrational fingerprints of the Raman- and infrared-active phonon modes. The analysis of thermodynamic properties reveals the Einstein temperature for CsTi 3 ⁢Te 5 , CsZr 3 ⁢Te 5 , and CsHf 3 ⁢Te 5 to be 66, 54, and 53 K, respectively. Our orbital-decomposed electronic structure calculations reveal significant in-plane steric interactions and multiple Dirac band crossings near the Fermi level. We further investigate the role of spin-orbit coupling effect on the studied properties. Furthermore, this theoretical investigation sheds light on the intriguing quantum behavior of kagome metals.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Unveiling and Mapping Polymorphs in Fluorite Y2TiO5 Using 4D-STEM and Unsupervised Machine Learning

Y2TiO5 belongs to the Ln2TiO5 (Ln = lanthanide or Y) family of ceramic materials and exhibits a range of desirable material properties such as radiation tolerance, frustrated magnetism, and large dielectric constant. However, understanding the complex crystal structure of Y2TiO5 remains elusive, given that Y2TiO5 can adopt multiple polymorphs such as cubic, orthorhombic, and hexagonal phases within the lattice. In this work, we report a detailed structural analysis of Y2TiO5 using four-dimensional scanning transmission electron microscopy coupled with unsupervised machine learning. The pyrochlore nanodomains, characterized by the ordered arrangement of yttrium cations on the A site of their A2BO5 structure, are present within the matrix of a predominantly fluorite-structured Y2TiO5 along with a third polymorph, the hexagonal phase. The pyrochlore phase is found to form 2 nm boundary regions around hexagonal phase stacking faults, highlighting the potential influence of the hexagonal phase on the occurrence and distribution of the pyrochlore phase. Lastly, we identify a unique pyrochlore phase with asymmetric arrangement of cation ordering along a single planar direction. Our findings provide invaluable insights into the possible mechanisms stabilizing pyrochlore nanodomains within the fluorite lattice of Y2TiO5.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structure of 3'-PO 4 /5'-OH RNA ligase RtcB in complex with a 5'-OH oligonucleotide

RtcB enzymes comprise a widely distributed family of manganese- and GTP-dependent RNA repair enzymes that join 2',3'-cyclic phosphate ends to 5'-OH ends via RtcB-(histidinyl-N)–GMP, RNA 3'-phosphate, and RNA 3 'pp 5 'G intermediates. RtcB can ligate either 5'-OH RNA or 5'-OH DNA strands in vitro. The nucleic acid contacts of RtcB are uncharted. In this work, we report a 2.7 Å crystal structure of Pyrococcus horikoshii RtcB in complex with a 6-mer 5'-OH DNA oligonucleotide HO A 1 pT 2 pG 3 pT 4 pC 5 pC 6 , which reveals enzymic contacts of Asn202 to the terminal 5'-OH nucleophile; Arg238 to the A1pT2 and T2pG3 phosphates; Arg190 and Gln194 to the T 2 pG 3 phosphate; and an Arg190 π-cation interaction with the G 3 nucleobase. The structural insights affirm functional studies of E. coli RtcB that implicated the conserved counterpart of Arg238 in engagement of the 5'-OH strand for ligation. The essential active site Cys98 that coordinates two manganese ions is oxidized to cysteine sulfonic acid in our structure, raising the prospect that RtcB activity might be sensitive to modulation during oxidative stress.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Materials Data on Ti2(Mo3Se4)5 by Materials Project

Ti2(Mo3Se4)5 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six Se2- atoms to form distorted TiSe6 octahedra that share corners with eight MoSe5 square pyramids, edges with four MoSe5 square pyramids, and faces with two MoSe5 square pyramids. There are a spread of Ti–Se bond distances ranging from 2.47–3.09 Å. In the second Ti4+ site, Ti4+ is bonded to six Se2- atoms to form distorted TiSe6 octahedra that share corners with eight MoSe5 square pyramids, edges with four MoSe5 square pyramids, and faces with two MoSe5 square pyramids. There are a spread of Ti–Se bond distances ranging from 2.48–3.09 Å. There are fifteen inequivalent Mo+2.13+ sites. In the first Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with three TiSe6 octahedra, corners with four MoSe5 square pyramids, and edges with five MoSe5 square pyramids. The corner-sharing octahedra tilt angles range from 39–54°. There are a spread of Mo–Se bond distances ranging from 2.53–2.73 Å. In the second Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with four MoSe5 square pyramids, an edgeedge with one TiSe6 octahedra, and edges with five MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.56–2.74 Å. In the third Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with four MoSe5 square pyramids, edges with five MoSe5 square pyramids, and a faceface with one TiSe6 octahedra. There are a spread of Mo–Se bond distances ranging from 2.58–2.66 Å. In the fourth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share a cornercorner with one TiSe6 octahedra, corners with four MoSe5 square pyramids, and edges with five MoSe5 square pyramids. The corner-sharing octahedral tilt angles are 56°. There are a spread of Mo–Se bond distances ranging from 2.56–2.67 Å. In the fifth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with four MoSe5 square pyramids, an edgeedge with one TiSe6 octahedra, and edges with five MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.57–2.77 Å. In the sixth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share a cornercorner with one TiSe6 octahedra, corners with four MoSe5 square pyramids, and edges with five MoSe5 square pyramids. The corner-sharing octahedral tilt angles are 40°. There are a spread of Mo–Se bond distances ranging from 2.53–2.71 Å. In the seventh Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with two equivalent TiSe6 octahedra, corners with four MoSe5 square pyramids, and edges with five MoSe5 square pyramids. The corner-sharing octahedra tilt angles range from 46–57°. There are a spread of Mo–Se bond distances ranging from 2.57–2.72 Å. In the eighth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with four MoSe5 square pyramids, edges with two TiSe6 octahedra, and edges with five MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.58–2.80 Å. In the ninth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share a cornercorner with one TiSe6 octahedra, corners with four MoSe5 square pyramids, edges with five MoSe5 square pyramids, and a faceface with one TiSe6 octahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Mo–Se bond distances ranging from 2.57–2.70 Å. In the tenth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share a cornercorner with one TiSe6 octahedra, corners with four MoSe5 square pyramids, edges with five MoSe5 square pyramids, and a faceface with one TiSe6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Mo–Se bond distances ranging from 2.57–2.66 Å. In the eleventh Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with four MoSe5 square pyramids, edges with two TiSe6 octahedra, and edges with five MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.58–2.78 Å. In the twelfth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with three TiSe6 octahedra, corners with four MoSe5 square pyramids, and edges with five MoSe5 square pyramids. The corner-sharing octahedra tilt angles range from 16–57°. There are a spread of Mo–Se bond distances ranging from 2.59–2.72 Å. In the thirteenth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with three equivalent TiSe6 octahedra, corners with four MoSe5 square pyramids, and edges with five MoSe5 square pyramids. The corner-sharing octahedra tilt angles range from 18–55°. There are a spread of Mo–Se bond distances ranging from 2.57–2.72 Å. In the fourteenth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with four MoSe5 square pyramids, edges with two equivalent TiSe6 octahedra, and edges with five MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.57–2.79 Å. In the fifteenth Mo+2.13+ site, Mo+2.13+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share a cornercorner with one TiSe6 octahedra, corners with four MoSe5 square pyramids, edges with five MoSe5 square pyramids, and a faceface with one TiSe6 octahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Mo–Se bond distances ranging from 2.57–2.70 Å. There are twenty inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four Mo+2.13+ atoms. In the second Se2- site, Se2- is bonded in a 1-coordinate geometry to one Ti4+ and three Mo+2.13+ atoms. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms. In the fourth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four Mo+2.13+ atoms. In the fifth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four Mo+2.13+ atoms. In the sixth Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms. In the seventh Se2- site, Se2- is bonded in a 6-coordinate geometry to three Mo+2.13+ atoms. In the eighth Se2- site, Se2- is bonded in a 4-coordinate geometry to four Mo+2.13+ atoms. In the ninth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four Mo+2.13+ atoms. In the tenth Se2- site, Se2- is bonded in a 4-coordinate geometry to one Ti4+ and three Mo+2.13+ atoms. In the eleventh Se2- site, Se2- is bonded in a 1-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms. In the twelfth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four Mo+2.13+ atoms. In the thirteenth Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms. In the fourteenth Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms. In the fifteenth Se2- site, Se2- is bonded in a 4-coordinate geometry to one Ti4+ and three Mo+2.13+ atoms. In the sixteenth Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms. In the seventeenth Se2- site, Se2- is bonded in a 1-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms. In the eighteenth Se2- site, Se2- is bonded in a 1-coordinate geometry to one Ti4+ and three Mo+2.13+ atoms. In the nineteenth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four Mo+2.13+ atoms. In the twentieth Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Mo+2.13+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb24(CuS8)5 by Materials Project

Nb24(CuS8)5 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are twenty-four inequivalent Nb+3.12+ sites. In the first Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted edge and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 46°. There are a spread of Nb–S bond distances ranging from 2.48–2.52 Å. In the second Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.48–2.53 Å. In the third Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.47–2.52 Å. In the fourth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.48–2.51 Å. In the fifth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.47–2.54 Å. In the sixth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.48–2.54 Å. In the seventh Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.48–2.50 Å. In the eighth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.47–2.52 Å. In the ninth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted edge and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 43°. There are a spread of Nb–S bond distances ranging from 2.49–2.54 Å. In the tenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are a spread of Nb–S bond distances ranging from 2.48–2.53 Å. In the eleventh Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 48–50°. There are a spread of Nb–S bond distances ranging from 2.48–2.57 Å. In the twelfth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted edge and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 46°. There are a spread of Nb–S bond distances ranging from 2.49–2.52 Å. In the thirteenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing NbS6 octahedra. There are a spread of Nb–S bond distances ranging from 2.47–2.60 Å. In the fourteenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 41–45°. There are a spread of Nb–S bond distances ranging from 2.48–2.55 Å. In the fifteenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 41–45°. There are a spread of Nb–S bond distances ranging from 2.50–2.55 Å. In the sixteenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing NbS6 octahedra. There are a spread of Nb–S bond distances ranging from 2.47–2.64 Å. In the seventeenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing NbS6 octahedra. There are a spread of Nb–S bond distances ranging from 2.47–2.64 Å. In the eighteenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 46–48°. There are a spread of Nb–S bond distances ranging from 2.48–2.55 Å. In the nineteenth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 46–48°. There are a spread of Nb–S bond distances ranging from 2.48–2.55 Å. In the twentieth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing NbS6 octahedra. There are a spread of Nb–S bond distances ranging from 2.48–2.59 Å. In the twenty-first Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 42–45°. There are a spread of Nb–S bond distances ranging from 2.48–2.52 Å. In the twenty-second Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 41–44°. There are a spread of Nb–S bond distances ranging from 2.48–2.55 Å. In the twenty-third Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 48–50°. There are a spread of Nb–S bond distances ranging from 2.48–2.57 Å. In the twenty-fourth Nb+3.12+ site, Nb+3.12+ is bonded to six S2- atoms to form a mixture of distorted edge and corner-sharing NbS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 43°. There are a spread of Nb–S bond distances ranging from 2.48–2.56 Å. There are five inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.24–2.35 Å. In the second Cu1+ site, Cu1+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.24–2.34 Å. In the third Cu1+ site, Cu1+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.23–2.34 Å. In the fourth Cu1+ site, Cu1+ is bonded in a distorted rectangular see-saw-like geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.20–2.34 Å. In the fifth Cu1+ site, Cu1+ is bonded in a distorted rectangular see-saw-like geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.22–2.35 Å. There are forty inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to three Nb+3.12+ and two equivalent Cu1+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three Nb+3.12+ atoms. In the third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the fifth S2- site, S2- is bonded in a distorted T-shaped geometry to three Nb+3.12+ atoms. In the sixth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the seventh S2- site, S2- is bonded in a 5-coordinate geometry to three Nb+3.12+ and two equivalent Cu1+ atoms. In the eighth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the ninth S2- site, S2- is bonded in a distorted T-shaped geometry to three Nb+3.12+ atoms. In the tenth S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the eleventh S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the twelfth S2- site, S2- is bonded in a distorted T-shaped geometry to three Nb+3.12+ atoms. In the thirteenth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the fourteenth S2- site, S2- is bonded in a 5-coordinate geometry to three Nb+3.12+ and two equivalent Cu1+ atoms. In the fifteenth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the sixteenth S2- site, S2- is bonded in a distorted T-shaped geometry to three Nb+3.12+ atoms. In the seventeenth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the eighteenth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the nineteenth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the twentieth S2- site, S2- is bonded to four Nb+3.12+ atoms to form distorted SNb4 trigonal pyramids that share a cornercorner with one SNb6 pentagonal pyramid, corners with two equivalent SNb4 trigonal pyramids, and edges with two equivalent SNb6 pentagonal pyramids. In the twenty-first S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the twenty-second S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the twenty-third S2- site, S2- is bonded in a 5-coordinate geometry to three Nb+3.12+ and two equivalent Cu1+ atoms. In the twenty-fourth S2- site, S2- is bonded to six Nb+3.12+ atoms to form distorted SNb6 pentagonal pyramids that share a cornercorner with one SNb6 pentagonal pyramid, edges with six SNb6 pentagonal pyramids, and edges with two equivalent SNb4 trigonal pyramids. In the twenty-fifth S2- site, S2- is bonded in a 5-coordinate geometry to five Nb+3.12+ atoms. In the twenty-sixth S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the twenty-seventh S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the twenty-eighth S2- site, S2- is bonded to six Nb+3.12+ atoms to form a mixture of distorted edge and corner-sharing SNb6 pentagonal pyramids. In the twenty-ninth S2- site, S2- is bonded to six Nb+3.12+ atoms to form distorted SNb6 pentagonal pyramids that share corners with two equivalent SNb6 pentagonal pyramids, a cornercorner with one SNb4 trigonal pyramid, and edges with seven SNb6 pentagonal pyramids. In the thirtieth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the thirty-first S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the thirty-second S2- site, S2- is bonded to six Nb+3.12+ atoms to form distorted SNb6 pentagonal pyramids that share corners with two equivalent SNb6 pentagonal pyramids, a cornercorner with one SNb4 trigonal pyramid, and edges with seven SNb6 pentagonal pyramids. In the thirty-third S2- site, S2- is bonded to six Nb+3.12+ atoms to form a mixture of distorted edge and corner-sharing SNb6 pentagonal pyramids. In the thirty-fourth S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.12+ atoms. In the thirty-fifth S2- site, S2- is bonded in a 6-coordinate geometry to three Nb+3.12+ and three Cu1+ atoms. In the thirty-sixth S2- site, S2- is bonded in a 5-coordinate geometry to five Nb+3.12+ atoms. In the thirty-seventh S2- site, S2- is bonded to six Nb+3.12+ atoms to form distorted SNb6 pentagonal pyramids that share a cornercorner with one SNb6 pentagonal pyramid, edges with six SNb6 pentagonal pyramids, and edges with two equivalent SNb4 trigonal pyramids. In the thirty-eighth S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Nb+3.12+ and one Cu1+ atom. In the thirty-ninth S2- site, S2- is bonded to four Nb+3.12+ atoms to form distorted SNb4 trigonal pyramids that share a cornercorner with one SNb6 pentagonal pyramid, corners with two equivalent SNb4 trigonal pyramids, and edges with two equivalent SNb6 pentagonal pyramids. In the fortieth S2- site, S2- is bonded in a distorted rectangu

36 MATERIALS SCIENCE↗
DOE OSTI2023

Highly Reversible Lithiation of Additive Free T‐Nb 2 O 5 for a Quarter of a Million Cycles

Abstract Fast energy storage via intercalation requires quick ionic diffusion and often results in pseudocapacitive behavior. The cycling stability of such energy storage materials remains understudied despite the relevance to lifetime cost. Orthorhombic niobium oxide (T‐Nb 2 O 5 ) is a rapid ion intercalation material with a theoretical capacity of 201.7 mAh g −1 (Li 2 Nb 2 O 5 ) and good cycling stability due to the minimal unit cell strain during (de)intercalation. Prior reports of T‐Nb 2 O 5 cycling between 1.3–3.1 V versus Li/Li + noted a 50% loss in capacity after 10 000 cycles. Here, cyclic voltammetry is used to identify the role of the voltage window, state of charge, and potentiostatic holds on the cycling stability of mesoporous T‐Nb 2 O 5 thin films. Films cycled between 1.2–3.0 V versus Li/Li + without voltage holds (Li 1.1 Nb 2 O 5 ) exhibited extreme cycling stability with 90.8% capacity retention after 0.25 million cycles without detectable morphological/crystallographic changes. In contrast, the inclusion of 60 s voltage holds (Li 2.18 Nb 2 O 5 ) led to rapid capacity loss with 61.6% retention after 10 000 cycles with corresponding X‐ray diffraction evidence of amorphization. Cycling with other limited voltage windows identifies that most crystallographic degradation occurs at higher extents of lithiation. These results reveal remarkable stability over limited conditions and suggest that T‐Nb 2 O 5 amorphization is associated with high extents of lithiation.

25 ENERGY STORAGE↗
DOE OSTI2020

ThH 5 : An Actinide–Containing Superhalogen Molecule

Thorium and its compounds have been widely investigated as important nuclear materials. Previous research focused on the potential use of thorium hydrides, such as ThH 2 , ThH 4 , and Th 4 H 15 , as nuclear fuels. Here, we report studies of the anion, ThH 5 , by anion photoelectron spectroscopy and computations. The resulting experimental and theoretical vertical detachment energies (VDE) for ThH 5 are 4.09 eV and 4.11 eV, respectively. These values and the agreement between theory and experiment facilitated the characterization of the structure of the ThH 5 anion and showed its neutral counterpart, ThH 5 to be a superhalogen. ThH 5 , which exhibits a C 4v structure with five Th–H single bonds, possesses the largest known H/M ratio among the actinide elements, M. Here, the adaptive natural density partitioning (AdNDP) method was used to further analyze the chemical bonding of ThH 5 – and to confirm the existence of five Th–H single bonds in the ThH 5 – molecular anion.

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

The Zintl Concept Applied to Intergrowth Structures: Electron‐Hole Matching, Stacking Preferences, and Chemical Pressures in Pd 5 InAs

Abstract Enumerating the potential stacking sequences of layers is a fundamental way to account for the structure diversity of solid state compounds. In many cases, these stacking variations represent polymorphs with only small energetic differences. Here, we examine a compound for which the preferred stacking pattern instead reveals key aspects about its chemical bonding: Pd 5 InAs. Its structure is based on the intergrowth of slabs of the AuCu 3 and PtHg 2 (or alternatively, fluorite) structure types. Two basic stacking arrangements are available to this compound, represented by the Pd 5 TlAs and HoCoGa 5 structure types. DFT total energy calculations reveal that the former outcompetes the latter by a staggering 0.65 eV/formula unit. Through a combination of DFT‐reversed approximation Molecular Orbital (DFT‐raMO) and DFT‐Chemical Pressure (DFT‐CP) analysis we trace this preference to two factors. First, with DFT‐raMO analysis, we derive a Zintl‐like bonding scheme of Pd 5 InAs. This scheme, along with the inspection of selected crystal orbitals, is then connected to preferred stacking through the coordination environments of the Pd atoms at the interface between the Pd−In and Pd−As layers. In the hypothetical HoCoGa 5 ‐type and observed Pd 5 InAs‐type structures, different Pd coordination environments arise at the interfaces. The hypothetical structure features square planar PdIn 2 As 2 units, in each of which the same 4d‐orbital serves in the Pd sublattice's role as both Lewis acid (for interactions with the As) and Lewis base (for interactions with the In). In the observed structure, tetrahedral PdIn 2 As 2 units occur instead, so that these contradictory roles are distributed to separate 4d‐orbitals, leading to more effective bonding. DFT‐CP analysis illustrates that this driving force for the Pd 5 TlAs‐type arrangement is supplemented by a favorable alignment of the packing tensions in the parent structures. Altogether, the resulting picture demonstrates how the reaction of simple intermetallic structures to form intergrowths can be guided by recognizable chemical interactions.

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

Resolving the ($\mathscr{g}$-2)$_μ$ discrepancy with $\mathcal{F}$–SU(5) intersecting D-branes

A discrepancy between the measured anomalous magnetic moment of the muon (g - 2) μ and computed Standard Model value now stands at a combined 4.2σ following experiments at Brookhaven National Lab (BNL) and the Fermi National Accelerator Laboratory (FNAL). A solution to the disagreement is uncovered in flipped SU(5) with additional TeV-Scale vector-like 10 +$\bar{10}$ multiplets and charged singlet derived from local F-Theory, collectively referred to as $\mathcal {F}$-SU(5). Here we engage general No-Scale supersymmetry (SUSY) breaking in $\mathcal {F}$-SU(5) D-brane model building to alleviate the (g-2)μ. tension between the Standard Model and observations. A robust Δa μ (SUSY) is realized via mixing of M 5 and M 1X at the secondary SU(5) x U(1) X unification scale in $\mathcal {F}$-SU(5) emanating from SU(5) breaking and U(1) X flux effects. Calculations unveil Δa μ (SUSY) = 19.0-22.3 x 10 -10 for gluino masses of M($\tilde{g}$ = 2.25-2.56 TeV nd higgsino dark matter, aptly residing within the BNL+FNAL 1σ mean. This (g – 2)μ favorable region of the model space also generates the correct light Higgs boson mass and branching ratios of companion rare decay processes, and is further consistent with all LHC Run 2 constraints. Finally, we also examine the heavy SUSY Higgs boson in light of recent LHC searches for an extended Higgs sector.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Creating Brønsted acidity at the SiO 2 -Nb 2 O 5 interface

Catalytically active acid sites associated with the silica-niobia interface were probed with a series of overcoated SiO 2 on Nb 2 O 5 (SiO 2 /Nb 2 O 5 ) mixed oxide materials prepared by deposition of tetraethyl orthosilicate onto niobic acid (Nb 2 O 5 nH 2 O) or calcined niobia (Nb 2 O 5 ). NH 3 TPD and pyridine DRIFTS studies indicated that the speciation of acid sites in the materials evolved as a function of SiO 2 loading, impacting the quantity and stability of Brønsted sites. Catalyst activity was highly dependent on SiO 2 loading in the liquid phase hydroalkoxylation of dihydropyran with n-octanol. At SiO 2 surface densities corresponding to approximately 1 Si per 2 surface Nb, the activity of these catalysts passed through a maximum approximately 20 times higher than the activity of calcined Nb 2 O 5 . We found that apparent reaction barriers measured over the most active SiO 2 /Nb 2 O 5 catalysts were 10 kJ/mol lower than those measured over niobic acid, suggesting that the OH features unique to the SiO 2 -Nb 2 O 5 interface were slightly more reactive than those on niobic acid.

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

Crystal Growth Scale-Up and Stability of RbSr 2 X 5 :Eu Scintillators

The discovery and development of new scintillation materials support national security needs. In these applications, large volumes of scintillator crystals are needed to achieve efficient screening for contraband. Therefore, one important step in the discovery of new scintillator compositions is testing their feasibility for scale-up and their stability. In this work, high-quality Ø22 mm crystals of two new scintillators RbSr 2 Br 5 :Eu and RbSr 2 I 5 :Eu were grown via the Vertical Bridgman method, and their scintillation properties were characterized. Here, the Ø22 mm RbSr 2 I 5 :Eu crystals could be grown with fast translation rates up to 3.5 mm/h. Both RbSr 2 Br 5 :Eu and RbSr 2 I 5 :Eu had high scintillation performance, including light yields of 46,000 and 61,000 ph/MeV, respectively, for Ø22 × 35 mm crystals. Additionally, properties related to physical stability were investigated, including the coefficients of thermal expansion via high-temperature X-ray diffraction (HTXRD) as well as moisture sensitivity. HTXRD confirmed the absence of solid–solid phase transitions and showed that RbSr 2 Br 5 had minimal thermal expansion anisotropy compared to RbSr 2 I 5 and some other inorganic metal halide scintillators, which favors the growth of large-sized crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Role of Eu-Doping in the Electron Transport Behavior in the Zintl Thermoelectric Ca 5-x-y Yb x Eu y Al 2 Sb 6 System

A series of Eu-doped Zintl compounds belonging to theCa 5-x-y Yb x Eu y Al 2 Sb 6 (x = 0, 1.12; 0 ≤ y ≤ 0.63(2)) system have been successfully synthesized by both the arc-melting and the molten Pb-flux methods. All of the five title compounds initially crystallized in the Ca 5 Ga 2 As 6 -type phase (space group Pbam, Z = 2, Pearson code oP26) and maintained their original structure even after the post-heat treatment, unlike the recently reported n-type Zintl analogues in the Ca 5-x-y Yb x RE y Al 2 Sb 6 (RE = Pr, Nd, Sm) systems, which underwent a phase transition from the Ca 5 Ga 2 As 6 -type to the Ca 5 Al 2 Bi 6 -type phase after annealing. This research aimed to understand the origin of the structural preference of the title Ca 5-x-y Yb x Eu y Al 2 Sb 6 system, whether it was affected by the valence electron count or the cationic size. Electrical transport property measurements showed an increase in electrical conductivities and a decrease of Seebeck coefficients for Ca 4.89(1) Eu 0.11 Al 2 Sb 6 , Ca 4.82(1) Eu 0.18 Al 2 Sb 6 , and Ca 4.62(1) Eu 0.38 Al 2 Sb 6 , compared to the parental compound Ca 5 Al 2 Sb 6 . Hole effect measurements proved that these changes should be attributed to the reduced carrier concentration and enhanced carrier mobility. The comprehensive density functional theory calculations including electron density map analysis for the hypothetical model Ca 4.5 Eu 0.5 Al 2 Sb 6 revealed that the polarity between Al and Sb forming the anionic frameworks decreased as the Eu-dopants were introduced, which eventually affected the carrier mobility in the anionic frameworks. Thermal conductivity measurements proved that the Eu-doping successfully lowered the lattice thermal conductivity because of the enhanced atomic disordering. In conclusion, the magnetization measurements for Ca 4.37(2) Eu 0.63 Al 2 Sb 6 showed a typical Curie–Weiss behavior with weak antiferromagnetic nearest-neighbor interactions with θ p = -5.07 K.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Quasi-One-Dimensional Structure and Possible Helical Antiferromagnetism of RbMn 6 Bi 5

Quasi-one-dimensional materials exhibit not only unique crystal structure but also abundant physical properties such as charge density wave, Luttinger liquid, and superconductivity. In this study, we report the discovery, structure, and physical properties of a new manganese-based quasi-one-dimensional material RbMn 6 Bi 5 , which crystallizes in a monoclinic space group C 2/ m (No. 12) with lattice parameters a = 23.286(5) Å, b = 4.6215(9) Å, c = 13.631(3) Å, and β = 125.00(3)°. The structure features [Mn 6 Bi 5 ] –1 double-walled column extending along the [010] direction, together with Bi–Bi homoatomic bonds linking the columns and the countercation Rb + . The temperature-dependent resistivity clearly indicates a significant resistivity anisotropy for RbMn 6 Bi 5 , whereas the magnetic susceptibility and specific heat measurements show that RbMn 6 Bi 5 is antiferromagnetic below 82 K. The density functional theory calculations indicate that RbMn 6 Bi 5 is a quasi-one-dimensional metal with possible helical antiferromagnetic configuration. The discovery of RbMn 6 Bi 5 confirms the viability of discovering new quasi-one-dimensional materials in manganese-based compounds.

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

Spin Reorientation in Antiferromagnetic Layered FePt 5 P

FePt 5 P, a substitutional variant of the anti-CeCoIn 5 structure type in the space group P4/mmm, was synthesized by a high-temperature solid-state method and structurally characterized by X-ray diffraction. FePt 5 P contains layers of FePt 12 clusters formed by magnetically active Fe and heavy Pt with strong spin-orbit coupling (SOC); the layers are separated by P atoms. The various Fe–Pt distances in FePt 12 clusters generate complex magnetic orders in FePt 5 P. According to temperature-dependent magnetic and specific heat measurements, FePt 5 P shows a stripe-type antiferromagnetic order at T N ≈ 90 K, which is also confirmed by resistivity measurements. Furthermore, a spin reorientation occurs at ~74 and ~68 K in and out of the ab plane based on the specific heat measurements. The temperature-dependent neutron powder diffraction patterns demonstrate the antiferromagnetic order in FePt 5 P, and the spins orientate up to 58.4° with respect to the c axis at 10 K. First-principles calculations of FePt 5 P show the band splitting at the Fermi level by strong SOC and the s–d hybridization between P and Fe/Pt electrons enhances the structural stability and affects the magnetic ordering.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ternary aromatic and anti-aromatic clusters derived from the hypho species [Sn 2 Sb 5 ] 3-

Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M 2 (CO) 6 Sn 2 Sb 5 ] 3- (M = Cr, Mo), and [(MSn 2 Sb 5 ) 2 ] 4- , (M = Cu, Ag)) in the process of capturing the hypho - [Sn 2 Sb 5 ] 3- in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo 2 (CO) 6 Sn 2 Sb 5 ] 3- stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn 2 Sb 5 ) 2 ] 4- and [(CuSn 2 Sb 5 ) 2 ] 4- render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn 2 Sb 5 ] 3- , thus providing conceptual advances in the field of metal-metal bonding in clusters.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Mg x Zn 1−x O contact to CuGa 3 Se 5 absorber for photovoltaic and photoelectrochemical devices

Abstract CuGa 3 Se 5 is a promising candidate material with wide band gap for top cells in tandem photovoltaic and photoelectrochemical (PEC) devices. However, traditional CdS contact layers used with other chalcopyrite absorbers are not suitable for CuGa 3 Se 5 due to the higher position of its conduction band (CB) minimum. Mg x Zn 1− x O (MZO) is a transparent oxide with adjustable band gap and CB position as a function of magnesium composition, but its direct application is hindered by CuGa 3 Se 5 surface oxidation. Here, MZO is investigated as a contact (n-type ‘buffer’ or ‘window’) material to CuGa 3 Se 5 absorbers pretreated in Cd 2+ solution, and an onset potential close to 1 V vs reversible hydrogen electrode in 10 mM hexaammineruthenium (III) chloride electrolyte is demonstrated. The Cd 2+ surface treatment changes the chemical composition and electronic structure of the CuGa 3 Se 5 surface, as demonstrated by photoelectron spectroscopy measurements. The performance of CuGa 3 Se 5 absorber with Cd 2+ treated surface in the solid-state test structure depends on the Zn/Mg ratio in the MZO layer. The measured open circuit voltage of 925 mV is promising for tandem PEC water splitting with CuGa 3 Se 5 /MZO top cells.

36 MATERIALS SCIENCE↗