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16 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Zn(HO)2 by Materials Project

Zn(OH)2 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one Zn(OH)2 sheet oriented in the (0, 0, 1) direction. Zn2+ is bonded to six equivalent O2- atoms to form edge-sharing ZnO6 octahedra. All Zn–O bond lengths are 2.14 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. O2- is bonded in a distorted single-bond geometry to three equivalent Zn2+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(HO)2 by Materials Project

Zn(OH)2 crystallizes in the monoclinic C2 space group. The structure is two-dimensional and consists of one Zn(OH)2 sheet oriented in the (0, 0, 1) direction. Zn2+ is bonded to six equivalent O2- atoms to form edge-sharing ZnO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.03–2.37 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. O2- is bonded in a distorted single-bond geometry to three equivalent Zn2+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(HO)2 by Materials Project

Zn(OH)2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. Zn2+ is bonded to four O2- atoms to form corner-sharing ZnO4 tetrahedra. There are a spread of Zn–O bond distances ranging from 1.98–2.00 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Zn2+ and one H1+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Zn2+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(HO)2 by Materials Project

Zn(OH)2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. Zn2+ is bonded to four O2- atoms to form corner-sharing ZnO4 tetrahedra. There are a spread of Zn–O bond distances ranging from 1.97–2.01 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Zn2+ and one H1+ atom. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Zn2+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2Zn17 by Materials Project

Ho2Zn17 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ho is bonded in a 10-coordinate geometry to nineteen Zn atoms. There are a spread of Ho–Zn bond distances ranging from 3.10–3.45 Å. There are four inequivalent Zn sites. In the first Zn site, Zn is bonded to three equivalent Ho and nine Zn atoms to form distorted ZnHo3Zn9 cuboctahedra that share corners with twenty-three ZnHo2Zn10 cuboctahedra, edges with ten ZnHo2Zn10 cuboctahedra, and faces with twenty ZnHo3Zn9 cuboctahedra. There are a spread of Zn–Zn bond distances ranging from 2.54–2.86 Å. In the second Zn site, Zn is bonded in a 2-coordinate geometry to one Ho and thirteen Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.64–2.98 Å. In the third Zn site, Zn is bonded to two equivalent Ho and ten Zn atoms to form ZnHo2Zn10 cuboctahedra that share corners with twenty-two ZnHo2Zn10 cuboctahedra, edges with ten ZnHo2Zn10 cuboctahedra, and faces with eighteen ZnHo3Zn9 cuboctahedra. All Zn–Zn bond lengths are 2.59 Å. In the fourth Zn site, Zn is bonded to two equivalent Ho and ten Zn atoms to form distorted ZnHo2Zn10 cuboctahedra that share corners with twenty-four ZnHo2Zn10 cuboctahedra, edges with five ZnHo2Zn10 cuboctahedra, and faces with twenty-one ZnHo3Zn9 cuboctahedra. Both Zn–Zn bond lengths are 2.67 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho13(Mg2Zn27)2 by Materials Project

Ho13(Mg2Zn27)2 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 6-coordinate geometry to three equivalent Ho and twelve Zn atoms. All Mg–Ho bond lengths are 3.11 Å. There are six shorter (2.82 Å) and six longer (3.15 Å) Mg–Zn bond lengths. In the second Mg site, Mg is bonded in a body-centered cubic geometry to eight Zn atoms. There are a spread of Mg–Zn bond distances ranging from 2.61–2.71 Å. There are four inequivalent Ho sites. In the first Ho site, Ho is bonded in a 3-coordinate geometry to sixteen Zn atoms. There are a spread of Ho–Zn bond distances ranging from 3.01–3.22 Å. In the second Ho site, Ho is bonded in a 12-coordinate geometry to one Mg and fourteen Zn atoms. There are a spread of Ho–Zn bond distances ranging from 3.00–3.29 Å. In the third Ho site, Ho is bonded in a 11-coordinate geometry to thirteen Zn atoms. There are a spread of Ho–Zn bond distances ranging from 2.96–3.24 Å. In the fourth Ho site, Ho is bonded in a 6-coordinate geometry to fourteen Zn atoms. There are a spread of Ho–Zn bond distances ranging from 2.88–3.49 Å. There are ten inequivalent Zn sites. In the first Zn site, Zn is bonded in a 10-coordinate geometry to four Ho and six Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.60–2.90 Å. In the second Zn site, Zn is bonded in a 1-coordinate geometry to two Mg, three Ho, and three Zn atoms. There are two shorter (2.62 Å) and one longer (2.63 Å) Zn–Zn bond lengths. In the third Zn site, Zn is bonded in a 9-coordinate geometry to three Ho and six Zn atoms. There are two shorter (2.55 Å) and two longer (2.88 Å) Zn–Zn bond lengths. In the fourth Zn site, Zn is bonded to two equivalent Ho and ten Zn atoms to form face-sharing ZnHo2Zn10 cuboctahedra. There are a spread of Zn–Zn bond distances ranging from 2.59–2.77 Å. In the fifth Zn site, Zn is bonded in a 12-coordinate geometry to four Ho and eight Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.54–2.97 Å. In the sixth Zn site, Zn is bonded in a 10-coordinate geometry to one Mg, four Ho, and five Zn atoms. There are two shorter (2.57 Å) and one longer (2.59 Å) Zn–Zn bond lengths. In the seventh Zn site, Zn is bonded in a 11-coordinate geometry to five Ho and six equivalent Zn atoms. In the eighth Zn site, Zn is bonded to three equivalent Ho and nine Zn atoms to form face-sharing ZnHo3Zn9 cuboctahedra. All Zn–Zn bond lengths are 2.65 Å. In the ninth Zn site, Zn is bonded in a 1-coordinate geometry to one Mg, three Ho, and five Zn atoms. In the tenth Zn site, Zn is bonded in a 1-coordinate geometry to one Mg, four Ho, and three Zn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tuning the Radius Ratio to Enhance Thermoelectric Properties in the Zintl Compounds AM 2 Sb 2 (A = Ba, Sr; M = Zn, Cd)

Five novel Zintl phase solid solutions in the Ba 1–x Sr x Zn 2–y Cd y Sb 2 (0 ≤ x ≤ 0.13(1); 0 ≤ y ≤ 0.32(2)) system were successfully synthesized by the molten Pb metal-flux method, and the powder X-ray diffraction and single-crystal X-ray diffraction analyses proved that all five title compounds adopted the BaCu 2 S 2 -type phase having the orthorhombic Pnma space group (Z = 4, Pearson code oP20) with five crystallographically independent atomic sites. The previously studied BaCu 2 S 2 -type antimonides demonstrated a limited tolerance for doping in contrast to the CaAl 2 Si 2 -type antimonides. To understand the relatively narrower phase width and limited dopability of the title BaCu 2 S 2 -type phase than the CaAl 2 Si 2 -type phase in the overall Ba 1–x Sr x Zn 2–y Cd y Sb 2 system, the radius ratio of cations and anionic elements r + /r – for two structure types were thoroughly investigated. For the first time, the r + /r – ratio was identified as a critical factor for the phase selectivity: (1) r + /r – > 1 favored the BaCu 2 S 2 -type phase, and (2) r + /r – < 1 favored the CaAl 2 Si 2 -type phase. Further, we also revealed the structural transformation mechanism from the more widely observed CaAl 2 Si 2 -type phase to the title BaCu 2 S 2 -type phase as the relatively larger cationic elements were introduced to the system. A series of DFT calculations using the three hypothetical models indicated that a resonance peak near EF in the density of states curves was descended from the relatively flat band structure at several special symmetry points rationalizing the enhanced Seebeck coefficients of Ba 0.94(1) Sr 0.06 Zn 1.86(3) Cd 0.14 Sb 2 and Ba 0.96(1) Sr 0.04 Zn 1.68(2) Cd 0.32 Sb 2 . Electron localization function analysis rationalized the correlation between the polarity change of anionic Zn/Cd–Sb bonds and the charge carrier mobility on the anionic frameworks. Temperature-dependent thermoelectric properties were studied for the four title compounds, and the results proved that the Sr and Cd doping in the title Ba 1–x Sr x Zn 2–y Cd y Sb 2 system successfully enhanced the ZT values through the increased Seebeck coefficients and the reduced total thermal conductivities.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2Zn(HO)6 by Materials Project

Sr2Zn(HO3)2(H2)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of four hydrogen molecules and one Sr2Zn(HO3)2 sheet oriented in the (-1, 0, 2) direction. In the Sr2Zn(HO3)2 sheet, Sr2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Sr–O bond distances ranging from 2.43–2.60 Å. Zn2+ is bonded in a distorted square co-planar geometry to six O2- atoms. There are a spread of Zn–O bond distances ranging from 1.96–2.57 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+, one Zn2+, and one O2- atom. The O–O bond length is 1.54 Å. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Sr2+, one Zn2+, and one H1+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Sr2+, one Zn2+, and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2Zn(HO)6 by Materials Project

Ba2Zn(HO)6 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Ba2Zn(HO)6 sheet oriented in the (-1, 0, 2) direction. Ba2+ is bonded in a 6-coordinate geometry to two H1+ and four O2- atoms. There are one shorter (2.84 Å) and one longer (2.96 Å) Ba–H bond lengths. There are a spread of Ba–O bond distances ranging from 2.50–2.79 Å. Zn2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (1.82 Å) and two longer (2.57 Å) Zn–O bond lengths. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a distorted water-like geometry to one Ba2+ and one H1+ atom. The H–H bond length is 0.76 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one H1+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one Ba2+ and one O2- atom. The H–O bond length is 0.99 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom. The O–O bond length is 1.50 Å. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, one Zn2+, and one O2- atom. In the third O2- site, O2- is bonded in a trigonal non-coplanar geometry to two equivalent Ba2+ and one Zn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Bridging Experiment and Theory to Reveal Compounds in K–Zn(Cd)–Bi Systems

This study investigates the facile hydride synthesis method guided by theoretical predictions to explore the K–T–Bi (T = Zn, Cd) phase spaces. Using an adaptive genetic algorithm (AGA) and density functional theory (DFT), candidate compositions are identified for experimental validation via a facile hydrides route, permitting experimental screening of K–Zn–Bi and “empty” K–Cd–Bi systems. The previously reported KZnBi and KZn 2 Bi 2 are synthesized alongside newly discovered KCdBi and KCd 2 Bi 2 . While the AGA and DFT predict the stability of these compounds, structural predictions align with the experiment only for KZnBi and KZn 2 Bi 2 . Single-crystal X-ray structure refinements confirm that KZnBi and KZn 2 Bi 2 adopt the hexagonal ZrBeSi- and tetragonal ThCr 2 Si 2 -structure types, respectively. KCdBi has tetragonal PbClF-structure type and KCd 2 Bi 2 belongs to the ThCr 2 Si 2 -structure type. A trend based on the ratio of the metal ionic radii allows to rationalize variation in the structure types within the ATBi family (A = Li–Cs), correctly identifying KCdBi as isostructural to NaZnBi. Thermal stability studied by high-temperature powder X-ray diffraction reveals that Zn-containing compounds melt at higher temperatures (821 K for KZn 2 Bi 2 ) than Cd-containing KCd 2 Bi 2 (635 K). This study highlights the efficacy of combining rapid synthesis techniques with predictive modeling, though structural predictions show some limitations in accuracy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Solutes that reduce yield strength anisotropies in magnesium from first principles

Using Labusch-type solid solution strengthening models parameterized with DFT-computed solute-dislocation interaction energies, we perform a computational search for 63 solutes across the periodic table to find those that lower anisotropy ratios (non-basal to basal CRSS) of magnesium potentially increasing its ductility per the von Mises criterion. For this purpose, we compute changes in strength for solutes as a function of composition and temperature, and compute anisotropy ratios for solutes that include both rare earth and non-rare earth elements. Here we specifically focus on solute-dislocation interaction energies in the following DFT-optimized dislocations as representative of three non-basal plastic deformation modes: $\langle c + a \rangle$ edge, (10$\bar1$2) tension twinning edge, and the (10$\bar{1}$1) compression twinning edge. We find that solute-induced changes in non-basal deformation modes can be approximated using a second-order polynomial in the size misfit of the solutes, which permits rapid screening of solutes. Our approach to identify solutes known to improve strengthening incorporates solute solubility, and suggests other solutes that not have been previously explored for strengthening. The 8 rare-earth solutes that our method suggests as the best, ordered by increasing anisotropy ratios at their optimal concentrations, are: Gd, Tb, Dy, Nd, Ho, Er, Tm, and Yb. The 12 non-rare-earth solutes that our method suggests as the best, ordered by increasing anisotropy ratios, are: Y, Mn, Sc, Pb, Ca, Ag, Bi, Tl, Zn, Li, Ga, and Al. Of these, Gd, Nd, Er, Yb, Y, Mn, Ca, Zn, Li, and Al are used in commercial Mg alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Kinetics of Direct Olefin Synthesis from Syngas over Mixed Beds of Zn–Zr Oxides and SAPO-34

A packed bed containing a physical mixture of both Zn–Zr mixed oxide catalyst and SAPO-34 converts syngas directly into a mixture of C 2 –C 5 olefins and paraffins. Specifically, the mixed oxide catalyst is responsible for intermediate oxygenate synthesis from syngas while the molecular sieve catalyzes olefin synthesis from the oxygenate intermediates. Kinetic measurements with cofed propylene over each catalyst independently confirm olefin hydrogenation activity over both components of the composite bed. The addition of either water or CO to the feed drops the activity of propylene hydrogenation over the Zn–Zr oxide. In sum, under reaction conditions of syngas feed and produced water, olefin hydrogenation predominantly occurs over the SAPO-34 catalyst, rather than over the catalyst responsible for hydrogenating CO into oxygenate intermediates. Here, a developed kinetic model consistent with this conclusion describes measurements at differing feed compositions, temperatures, space velocities, and bed catalyst mixing ratios. Technoeconomic analysis of the process indicates that the olefin-to-paraffin ratio is a key performance metric for commercial scale syngas conversion and highlights the importance of considering olefin hydrogenation rates over the molecular sieve component.

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

Overcoming the doping limit in GaAs by ion implantation and pulsed laser melting

Most semiconductors exhibit a saturation of free carriers when heavily doped with extrinsic dopants. This carrier saturation or “doping limit” is known to be related to the formation of native compensating defects, which, in turn, depends on the energy positions of their conduction band minimum and valence band maximum. Here, we carried out a systematic study on the n-type doping limit of GaAs via ion implantation and showed that this doping limitation can be alleviated by the transient process of pulsed laser melting (PLM). For n-type doping, both group VI (S) and amphoteric group IV (Si and Ge) dopants were implanted in GaAs. For comparison, p-type doping was also studied using Zn as the acceptor. Implanted dopants were activated by the PLM method, and the results are compared to rapid thermal annealing (RTA). Our results reveal that for all n-type dopants, while implantation followed by the RTA results in a similar saturation electron concentration of 2–3 × 10 18 cm –3 , the transient PLM process is capable of trapping high concentration of dopants in the substitutional site, giving rise to a carrier concentration of >10 19 cm –3 , exceeding the doping limit of GaAs. However, due to scatterings from point defects generated during PLM, the mobility of n-type GaAs after PLM is low (~80–260 cm 2 /V s). Subsequent RTA after PLM (PLM + RTA) is able to remove these point defects and recover the mobility to ~1000–2000 cm2/V s. The carrier concentrations of these PLM + RTA samples are reduced but are still a factor of 3 higher than RTA only GaAs. This can be understood as the dopants are already incorporated in the substitutional site after PLM; they are less likely to be “deactivated” by subsequent RTA. This work is significant to the understanding of doping mechanisms in semiconductors and provides a means for device applications, which require materials with ultra-high doping.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Stable bismuth-antimony alloy cathode with a conversion-dissolution/deposition mechanism for high-performance zinc batteries

Although a large number of intercalation cathode materials for aqueous Zn batteries have been reported, limited intercalation capacity precludes achieving a higher energy density. Here, for this work, we develop a high-performance aqueous Zn battery based on BiSb alloy (Bi 0.5 Sb 0.5 ) using a high-concentrated strong-basic polyelectrolyte. We demonstrate that a conversion-dissolution/deposition electrochemical mechanism (BiSb ↔ Bi + SbO 2 – ↔ Bi + SbO 3 – ↔ Bi 2 O 3 ) through in situ X-ray diffraction (XRD), Raman, and ex-situ X-ray photoelectron spectrometry (XPS) characterizations with the help of density functional theory calculations. The BiSb cathode delivers large capacity of 512 mAh g –1 at 0.3 Ag –1 and superior rate capability of 90 mAh g –1 even at 20 Ag –1 , and long-term cyclability with capacity retentions of 184 mAh g –1 after 600 cycles at 0.5 Ag –1 and 130 mAh g –1 after 1300 cycles at 1 Ag –1 . Remarkably, even at temperatures as low as –10 and –20 °C, capacities of 210 and 197 mAh g –1 are reserved at 1 Ag –1 , respectively. Moreover, the prepared pouch Zn//BiSb battery delivers a high energy density of 303 Wh kg –1 BiSb at 0.3 Ag –1 . When coupled with a high concentration polyelectrolyte, the Zn/BiSb battery exhibits an excellent performance over a wide temperature range (–40 to 40 °C). Our research reveals the metal cathode is promising for Zn batteries to achieve a high performance with the unique mechanism and alloys can be an effective approach to stabilize metal electrodes for cycling.

25 ENERGY STORAGE↗
DOE OSTI2026

Suppressing CO formation in low-temperature methanol steam reforming via Ce-modified CuZnGa layered oxide catalysts

Cu-based layered double hydroxides (LDHs) are widely recognized as effective catalysts for low-temperature methanol steam reforming, yet achieving high hydrogen productivity together with near-complete suppression of CO formation remains challenging. Here, we report the synthesis and evaluation of a series of CuZnGa LDH-derived catalysts and Ce-modified analogues prepared via an aqueous miscible organic method, which enables high metal dispersion and precise structural control. The optimized CuZnGa catalyst exhibits a hydrogen production rate of 16.9 µmol H 2 ·g cat −1 ·s −1 at 180 °C with an H 2 /CO ratio exceeding 3500, outperforming many state-of-the-art low-temperature systems. Importantly, the incorporation of small amounts of Ce further suppresses CO formation while maintaining high hydrogen productivity. Combined spectroscopic characterization and density functional theory calculations reveal that Ce is incorporated into the LDH lattice by substituting Ga 3+ sites up to a critical threshold, beyond which highly dispersed CeO x species are formed. These species provide mobile lattice oxygen that participates in a Mars-van Krevelen-type pathway, selectively oxidizing CO and suppressing the reverse water-gas shift reaction. This study establishes a clear relationship between Ce speciation, oxygen mobility, and catalytic selectivity in LDH-derived systems. The resulting catalysts demonstrate the potential of interface-engineered Cu-based materials for efficient low-temperature hydrogen production with minimal CO contamination.

09 BIOMASS FUELS↗