Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Rb”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Rb(CoP)2 by Materials Project

Rb(CoP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb1+ is bonded in a distorted body-centered cubic geometry to eight equivalent P3- atoms. All Rb–P bond lengths are 3.48 Å. Co+2.50+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing CoP4 tetrahedra. All Co–P bond lengths are 2.20 Å. P3- is bonded in a 8-coordinate geometry to four equivalent Rb1+ and four equivalent Co+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(GeAs)3 by Materials Project

Rb(GeAs)3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Rb1+ is bonded in a 6-coordinate geometry to six As3- atoms. There are a spread of Rb–As bond distances ranging from 3.46–3.93 Å. There are three inequivalent Ge+2.67+ sites. In the first Ge+2.67+ site, Ge+2.67+ is bonded to four As3- atoms to form corner-sharing GeAs4 tetrahedra. There are a spread of Ge–As bond distances ranging from 2.45–2.50 Å. In the second Ge+2.67+ site, Ge+2.67+ is bonded in a distorted trigonal non-coplanar geometry to three As3- atoms. There are one shorter (2.52 Å) and two longer (2.53 Å) Ge–As bond lengths. In the third Ge+2.67+ site, Ge+2.67+ is bonded in a water-like geometry to two equivalent As3- atoms. Both Ge–As bond lengths are 2.56 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded to three equivalent Rb1+ and three Ge+2.67+ atoms to form distorted AsRb3Ge3 octahedra that share corners with two equivalent AsRb2Ge3 square pyramids, edges with four equivalent AsRb3Ge3 octahedra, and edges with three equivalent AsRb2Ge3 square pyramids. In the second As3- site, As3- is bonded to two equivalent Rb1+ and three Ge+2.67+ atoms to form distorted AsRb2Ge3 square pyramids that share corners with two equivalent AsRb3Ge3 octahedra, edges with three equivalent AsRb3Ge3 octahedra, and edges with two equivalent AsRb2Ge3 square pyramids. The corner-sharing octahedral tilt angles are 18°. In the third As3- site, As3- is bonded in a rectangular see-saw-like geometry to one Rb1+ and three Ge+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(AsRu)2 by Materials Project

Rb(RuAs)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb1+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. All Rb–As bond lengths are 3.65 Å. Ru+2.50+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing RuAs4 tetrahedra. All Ru–As bond lengths are 2.44 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Rb1+ and four equivalent Ru+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(PRu)2 by Materials Project

Rb(RuP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb1+ is bonded in a body-centered cubic geometry to eight equivalent P3- atoms. All Rb–P bond lengths are 3.62 Å. Ru+2.50+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing RuP4 tetrahedra. All Ru–P bond lengths are 2.32 Å. P3- is bonded in a 8-coordinate geometry to four equivalent Rb1+ and four equivalent Ru+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(IrO2)6 by Materials Project

Rb(IrO2)6 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. Rb1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.86 Å) and four longer (3.40 Å) Rb–O bond lengths. There are two inequivalent Ir+3.83+ sites. In the first Ir+3.83+ site, Ir+3.83+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing IrO6 octahedra. The corner-sharing octahedra tilt angles range from 52–53°. There are a spread of Ir–O bond distances ranging from 1.98–2.07 Å. In the second Ir+3.83+ site, Ir+3.83+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing IrO6 octahedra. The corner-sharing octahedra tilt angles range from 52–53°. There are a spread of Ir–O bond distances ranging from 1.98–2.07 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Rb1+ and three Ir+3.83+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Rb1+ and three Ir+3.83+ atoms. In the third O2- site, O2- is bonded in a trigonal planar geometry to three Ir+3.83+ atoms. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to three Ir+3.83+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(Nb2Cl5)3 by Materials Project

Rb(Nb2Cl5)3 crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. Rb1+ is bonded in a distorted q6 geometry to ten Cl1- atoms. There are a spread of Rb–Cl bond distances ranging from 3.33–3.50 Å. There are five inequivalent Nb+2.33+ sites. In the first Nb+2.33+ site, Nb+2.33+ is bonded to five Cl1- atoms to form distorted corner-sharing NbCl5 square pyramids. There are a spread of Nb–Cl bond distances ranging from 2.46–2.83 Å. In the second Nb+2.33+ site, Nb+2.33+ is bonded to five Cl1- atoms to form corner-sharing NbCl5 square pyramids. There are a spread of Nb–Cl bond distances ranging from 2.46–2.72 Å. In the third Nb+2.33+ site, Nb+2.33+ is bonded to five Cl1- atoms to form corner-sharing NbCl5 square pyramids. There are a spread of Nb–Cl bond distances ranging from 2.47–2.71 Å. In the fourth Nb+2.33+ site, Nb+2.33+ is bonded to five Cl1- atoms to form corner-sharing NbCl5 square pyramids. There are four shorter (2.50 Å) and one longer (2.69 Å) Nb–Cl bond lengths. In the fifth Nb+2.33+ site, Nb+2.33+ is bonded to five Cl1- atoms to form corner-sharing NbCl5 square pyramids. There are four shorter (2.47 Å) and one longer (2.72 Å) Nb–Cl bond lengths. There are eleven inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a rectangular see-saw-like geometry to two equivalent Rb1+ and two equivalent Nb+2.33+ atoms. In the second Cl1- site, Cl1- is bonded in a distorted square co-planar geometry to two equivalent Rb1+ and two Nb+2.33+ atoms. In the third Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent Nb+2.33+ atoms. In the fourth Cl1- site, Cl1- is bonded in a 3-coordinate geometry to one Rb1+ and two Nb+2.33+ atoms. In the fifth Cl1- site, Cl1- is bonded in a 3-coordinate geometry to one Rb1+ and two Nb+2.33+ atoms. In the sixth Cl1- site, Cl1- is bonded in a 3-coordinate geometry to one Rb1+ and two Nb+2.33+ atoms. In the seventh Cl1- site, Cl1- is bonded in a 3-coordinate geometry to one Rb1+ and two Nb+2.33+ atoms. In the eighth Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent Nb+2.33+ atoms. In the ninth Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent Nb+2.33+ atoms. In the tenth Cl1- site, Cl1- is bonded in a 2-coordinate geometry to two equivalent Nb+2.33+ atoms. In the eleventh Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to two Nb+2.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(WO3)3 by Materials Project

Rb(WO3)3 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. Rb1+ is bonded to twelve O2- atoms to form RbO12 cuboctahedra that share edges with twelve equivalent WO6 octahedra and faces with two equivalent RbO12 cuboctahedra. There are a spread of Rb–O bond distances ranging from 3.23–3.48 Å. W+5.67+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six equivalent WO6 octahedra and edges with four equivalent RbO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 10–32°. There are a spread of W–O bond distances ranging from 1.94–1.96 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Rb1+ and two equivalent W+5.67+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Rb1+ and two equivalent W+5.67+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent W+5.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(CoAs)2 by Materials Project

Rb(CoAs)2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb1+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. All Rb–As bond lengths are 3.53 Å. Co+2.50+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing CoAs4 tetrahedra. All Co–As bond lengths are 2.32 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Rb1+ and four equivalent Co+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

ASb 3 Mn 9 O 19 (A = K or Rb): New Mn-Based 2D Magnetoplumbites with Geometric and Magnetic Frustration

Magnetoplumbites are one of the most broadly studied families of hexagonal ferrites, typically with high magnetic ordering temperatures, making them excellent candidates for permanent magnets. However, magnetic frustration is rarely observed in magnetoplumbites. Herein, the discovery, synthesis, and characterization of the first Mn-based magnetoplumbite, as well as the first magnetoplumbite involving pnictogens (Sb), ASb 3 Mn 9 O 19 (A = K or Rb) are reported. The Mn 3+ ( S = 2) cations, further confirmed by DC magnetic susceptibility and X-ray photoelectron spectroscopy, construct three geometrically frustrated sublattices, including Kagome, triangular, and puckered honeycomb lattices. Magnetic properties measurements revealed strong antiferromagnetic spin–spin coupling as well as multiple low-temperature magnetic features. Heat capacity data does not show any prominent λ-anomaly, suggesting minimal associated magnetic entropy. Moreover, neutron powder diffraction (NPD) implied the absence of long-range magnetic ordering in KSb 3 Mn 9 O 19 down to 3 K. However, several magnetic peaks are observed in RbSb 3 Mn 9 O 19 at 3 K, corresponding to an incommensurate magnetic structure. Interestingly, strong diffuse scattering is seen in the NPD patterns of both compounds at low angles and is analyzed by reverse Monte Carlo refinements, indicating short-range spin ordering related to frustrated magnetism as well as 2D magnetic correlations in ASb 3 Mn 9 O 19 (A = K or Rb).

2-D magnetic correlation↗
DOE OSTI2024

Molten Flux Synthesis of Plutonium (IV) Silicates K 2 PuSi 2 O 7 and Rb 2 PuSi 6 O 15

Few plutonium containing silicates have been reported in the literature and only one other tetravalent plutonium silicate structure has been reported using the flux growth method. With the goal of understanding actinide incorporation into silicates, we describe herein two new plutonium (IV) silicates, Rb 2 PuSi 6 O 15 and K 2 PuSi 2 O 7 , synthesized using a mixed alkali chloride/alkali fluoride flux growth. Both structures crystallize in the C2/c space group with lattice parameters a=24.2980(10) Å, b=7.1466(3) Å, c=17.2025(8) Å and $\blacksquare$96.6560(10)° for Rb 2 PuSi 6 O 15 , and a=9.9478(2) Å, b=5.59820 (10) Å, c=13.1848(2) Å, and $\blacksquare$105.7400(10)° for K 2 PuSi 2 O 7 . Comparisons to the synthesis of other reported alkali actinide silicates (Ce, U, and Th) are made. Raman spectra and DFT calculations of formation enthalpies and vibrational modes provide confirmation of structure refinements and enhanced product characterization for comparison with other materials.

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

Multiplexed fitness profiling by RB-TnSeq elucidates pathways for lignin-related aromatic catabolism in Sphingobium sp. SYK-6

Bioconversion of lignin-related aromatic compounds relies on robust catabolic pathways in microbes. Sphingobium sp. SYK-6 (SYK-6) is a well-characterized aromatic catabolic organism that has served as a model for microbial lignin conversion, and its utility as a biocatalyst could potentially be further improved by genome-wide metabolic analyses. To this end, we generate a randomly barcoded transposon insertion mutant (RB-TnSeq) library to study gene function in SYK-6. The library is enriched under dozens of enrichment conditions to quantify gene fitness. Several known aromatic catabolic pathways are confirmed, and RB-TnSeq affords additional detail on the genome-wide effects of each enrichment condition. Selected genes are further examined in SYK-6 or Pseudomonas putida KT2440, leading to the identification of new gene functions. The findings from this study further elucidate the metabolism of SYK-6, while also providing targets for future metabolic engineering in this organism or other hosts for the biological valorization of lignin.

09 BIOMASS FUELS↗
DOE OSTI2022

Magnetic phase diagram of A 2 [FeCl 5 (H 2 O)] ( A = K, Rb, NH 4 )

Here, erythrosiderites with the formula A 2 FeX 5 ∙H 2 O, where A = Rb, K, and (NH 4 ) and X = Cl and Br are intriguing systems that possess various magnetic and electric phases, as well as multiferroic phases in which magnetism and ferroelectricity are coupled. In this report, we study the magnetic phase diagram of erythrosiderites as a function of superexchange interactions and magnetic anisotropies. To this end, we perform classical Monte Carlo simulations on magnetic Hamiltonians that contain five different superexchange interactions with single-ion anisotropies. Our phase diagram contains all magnetic ground states that have been experimentally observed in these materials. We argue that the ground states can be explained by varying the ratio of $\frac{J_4}{J_2}$. For $\frac{J_4}{J_2}$ > 0.95 a cycloidal spins structure is stabilized as observed in (NH 4 ) 2 FeCl 5 ∙H 2 O and otherwise a collinear spin structure is stabilized as observed in (K,Rb) 2 FeCl 5 ∙H 2 O. We also show that the difference in the single-ion anisotropy along a- and c- axes is essential to stabilize the intermediate state observed in (NH) 2 FeCl 5 ∙H 2 O.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Salt-flux synthesis, crystal structure and theoretical characterization of Rb 0.74 Ga 6.62 Ti 0·38 O 11

Here single crystals of Rb 0.74 Ga 6.62 Ti 0·38 O 11 (RGTO) were grown from a mixed RbCl–RbF flux at 850 °C. The compound crystallizes in the RbGa 7 O 11 structure type, which is reminiscent of the hollandite and β-Ga 2 O 3 structure types. RGTO crystallizes in the monoclinic space group P2/m with lattice parameters a = 8.3355 (8) Å, b = 3.0286 (3) Å, c = 9.5028 (9) Å, and β = 114.620 (3)°. The crystal structure of RGTO is comprised of GaO 6 and mixed (Ga/Ti)O 6 octahedra and GaO 4 tetrahedra connected in a complex three-dimensional, anionic framework exhibiting eight-sided channels that are occupied by disordered Rb cations required for charge balance. First-principles calculations in the form of density functional theory were performed, which indicated the complex to be a charge transfer semiconductor.

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

RB-TnSeq identifies genetic targets for improved tolerance of Pseudomonas putida towards compounds relevant to lignin conversion

We report lignin-derived mixtures intended for bioconversion commonly contain high concentrations of aromatic acids, aliphatic acids, and salts. The inherent toxicity of these chemicals places a significant bottleneck upon the effective use of microbial systems for the valorization of these mixtures. Pseudomonas putida KT2440 can tolerate stressful quantities of several lignin-related compounds, making this bacterium a promising host for converting these chemicals to valuable bioproducts. Nonetheless, further increasing P. putida tolerance to chemicals in lignin-rich substrates has the potential to improve bioprocess performance. Accordingly, we employed random barcoded transposon insertion sequencing (RB-TnSeq) to reveal genetic determinants in P. putida KT2440 that influence stress outcomes during exposure to representative constituents found in lignin-rich process streams. The fitness information obtained from the RB-TnSeq experiments informed engineering of strains via deletion or constitutive expression of several genes. Namely, ΔgacAS, ΔfleQ, ΔlapAB, ΔttgR::P tac :ttgABC, Ptac:PP_1150:PP_1152, ..delta..relA, and ΔPP_1430 mutants showed growth improvement in the presence of single compounds, and some also exhibited greater tolerance when grown using a complex chemical mixture representative of a lignin-rich chemical stream. Overall, this work demonstrates the successful implementation of a genome-scale screening tool for the identification of genes influencing stress tolerance against notable compounds within lignin-enriched chemical streams, and the genetic targets identified herein offer promising engineering targets for improving feedstock tolerance in lignin valorization strains of P. putida KT2440.

09 BIOMASS FUELS↗
DOE OSTI2020

Ultralow Thermal Conductivity and Thermoelectric Properties of Rb 2 Bi 8 Se 13

Complex bismuth chalcogenides are narrow band gap semiconductors with intrinsic low thermal conductivity, which exhibit high potential as highly efficient thermoelectric materials. Here, we assess the basic thermoelectric properties of polycrystalline Rb 2 Bi 8 Se 13 in the temperature range 300-823 K as well as performance-optimizing strategies. We find that the as-made bulk samples are single phase with the monoclinic crystal structure (P2 1 /m) and crystallize in layer morphology. The pristine sample exhibits an exceedingly low lattice thermal conductivity of 0.6- 0.46 W·m -1 ·K -1 at 300-823 K, which derives from strong lattice anharmonicity, large Grüneisen parameters, and low phonon velocities induced by the complex crystal structure with heavy atom Bi and a large unit cell. Here, the Cl doping successfully enhances the carrier concentration in Rb 2 Bi 8 Se 13 with a negligible impact on the electronic band structure, displaying common doping behaviors. Se vacancy, on the contrary, leads to n-type doping and enhances the effective mass and power factors more significantly. Consequently, a maximum ZT of ~0.75 at 823 K for the 0.3% Se-vacancy-doped sample is obtained.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A Ba 6 Cu 31 Te 22 ( A = K, Rb, Cs) Featuring Polyanionic Copper–Telluride Frameworks with Ultralow Thermal Conductivity

In this study, hree polyanionic tellurides, ABa 6 Cu 31 Te 22 (A = K, Rb, Cs), were synthesized in salt flux. The isostructural tellurides crystallize in a new structure type, in the cubic Pa$\overline{3}$ space group with a Wyckoff sequence of d 10 c 2 b 1 and large unit cell volumes of over 5500 Å 3 . The structures feature a framework of [CuTe 4 ] tetrahedra and [CuTe 3 ] trigonal pyramids with disorder in the Cu sites. The polyanionic frameworks have large square antiprism and cuboctahedral voids where Ba and alkali metal cations are situated, forming [BaTe 8 ] and [ATe 12 ], respectively. The overall compositions are close to being charge balanced. The large [ATe 12 ] cuboctahedra allowed for significant anisotropic displacement of the A cations, as observed from both single crystal X-ray diffraction and heat capacity studies. Alkali cations rattling together with Cu atom displacement and disorder leads to the dispersion of phonons, thus softening the lattice and subsequently reducing the thermal conductivity. Evaluations of the electronic band structure revealed the occurrence of a narrow bandgap together with the presence of a flat band near the valence band maximum, giving rise to the high thermopower. The Cs and Rb analogues show a slope change in the temperature dependence of electrical resistivity around room temperature, which is typical for semimetals or degenerate semiconductors. For the as-synthesized and unoptimized materials, high values of the thermoelectric figure-of-merit of ~0.2 were observed at 623 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Non-adiabatic quantum interference and complex formation in ultracold collisions of Rb with KRb

Ultracold elastic collisions of 87 Rb with 40 K 87 Rb in its ground vibrational and rotational state are investigated using a first principles based theoretical methodology. Full-dimensional ab initio computed potential energy surfaces are reported that include the two lowest-lying electronic states, their conical intersection, non-adiabatic couplings and an accurate long-range behavior. A numerically exact time-independent quantum dynamics method in hyperspherical coordinates is used to compute the elastic scattering cross sections, rate coefficients and collision lifetime spectrum. The quantum scattering calculations include all degrees of freedom and treat both electronic states and their non-adiabatic couplings using a two-state diabatic representation. The theoretically computed elastic rate coefficient is in good agreement with the recently reported experimental value. Significant non-adiabatic quantum interference effects are shown to originate from the unique properties of ultracold collisions and the geometric phase associated with the conical intersection. A high-resolution collision energy grid is used to investigate the origin of the experimentally reported long-lived 3-body collision complexes.

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

Synthesis and anisotropic magnetism in quantum spin liquid candidates A YbSe 2 ( A = K and Rb)

The quantum spin liquid (QSL) state in rare-earth triangular lattices has attracted much attention recently due to its potential application in quantum computing and communication. Here, we report the single-crystal growth synthesis, crystal structure characterizations, and magnetic properties of AYbSe 2 (A = K and Rb) compounds. The x-ray diffraction analysis shows that AYbSe 2 (A = K and Rb) crystallizes in a trigonal space group, R-3m (No. 166) with Z = 3. AYbSe 2 possesses a two-dimensional (2D) Yb–Se–Yb layered structure formed by edged-shared YbSe 6 octahedra. The magnetic properties are highly anisotropic for both title compounds, and no long-range order is found down to 0.4 K, revealing the possible QSL ground state in these compounds. The isothermal magnetization exhibits a one-third magnetization plateau when the magnetic fields are applied in the ab-plane. Heat capacity is performed along both ab-plane and c axis and features the characteristic dome for triangular magnetic lattice compounds as a function of magnetic fields. Due to the change in the interlayer and intralayer distance of Yb 3+ , the dome shifts to low fields from KYbSe 2 to RbYbSe 2 . All these results indicate that the AYbSe 2 family presents unique frustrated magnetism close to the possible QSL and noncollinear spin states.

36 MATERIALS SCIENCE↗