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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Calorimetric Study of Mixed Phosphates Na 4 M 3 (PO 4 ) 2 P 2 O 7 (M = Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ ) to Evaluate the Electrochemical Trends

Mixed polyanionic compounds have been studied extensively as viable cathode materials for sodium-ion batteries. Mixed phosphates, Na 4 M 3 (PO 4 ) 2 P 2 O 7 (M = Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ ), provide a low barrier for Na-ion diffusion, being advantageous in comparison to phosphates and pyrophosphates. The reported order of sodium extraction is ambiguous and remains unclear. Despite being structurally similar, electrochemical performance differs for all four analogues with different degrees of (de)sodiation, according to the transition element present. High-temperature oxide melt solution calorimetry has been used to establish the relation between thermodynamic phase stability and observed capacity for this series of mixed phosphates. Thermodynamic phase stability largely depends on the kind of structure, type of bonding, and size of the cations present. So, according to our results, the thermodynamic phase stability follows the order Na 4 Mn 3 (PO 4 ) 2 P 2 O 7 > Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 > Na 4 Co 3 (PO 4 ) 2 P 2 O 7 > Na 4 Ni 3 (PO 4 ) 2 P 2 O 7 . The thermodynamic studies serve as guidelines for the selection of compositions with the potential for fabricating advanced cathode materials with maximum performance.

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

Deciphering the Mechanistic Role of Individual Oxide Phases and Their Combinations in Supported Mn–Na 2 WO 4 Catalysts for Oxidative Coupling of Methane

Oxidative coupling of methane (OCM) is an attractive direct route for upgrading methane to valuable chemicals. In this study, Temporal Analysis of Products (TAP) and steady state experiments are conducted to understand the role of individual oxide phases and their combinations in supported Mn-Na 2 WO 4 /SiO 2 catalysts for OCM. The results from TAP transient kinetic studies indicate that Mn plays an important role in promoting gas phase oxygen activation, while NaO x /SiO 2 and WO x /SiO 2 are relatively inert towards gas phase oxygen and methane activation. However, the supported catalyst combining Na and W in the form Na 2 WO 4 show enhanced gas phase oxygen activation exhibiting a much lower oxygen activation energy (148 kJ/mol) and enhanced activity toward methane activation as compared to the individual supported oxide catalysts. Addition of Mn to Na 2 WO 4 /SiO 2 further decreases the oxygen activation energy by 40 kJ/mol. Moreover, methane activation is also enhanced with CH 3 as the main intermediate but, with increasing Mn content, more CH 2 intermediates are observed. Different forms of oxygen (both dioxygen and atomic) are detected on the catalyst surface using isotopic pump/probe pulsing and their distribution is found to depend on the catalyst composition. An optimal Mn content in the Na 2 WO 4 /SiO 2 catalyst system is needed to enhance the amount of dioxide surface species (e.g., superoxide 16 O 2 - or peroxide 16 O 2 2- ) associated with the Na 2 WO 4 leading to high C 2 selectivity for OCM. When the Mn content is too high, the larger MnOx domains are shown to contribute to the formation of higher concertation of monoxide surface species that lead to nonselective OCM pathways. This insight from transient kinetic characterization using TAP combined with conventional steady state studies, provides a deeper understanding of the role of individual oxide phases and their combination on supported catalysts toward the formation of intermediate surface species and their impact on the OCM reaction mechanism. This knowledge is critical toward designing superior catalyst formulations for OCM.

10 SYNTHETIC FUELS↗
DOE OSTI2025

Stable-Cycling Sustainable Na-Ion Batteries with Olivine Iron Phosphate Cathode in an Ether Electrolyte

Sustainable batteries using nontoxic, earth-abundant, and low-cost materials are key to decarbonization. Olivine NaFePO 4 fulfills these criteria, is attractive for Na-ion batteries, and can be derived from LiFePO 4 recycled from Li-ion battery wastes. Critical knowledge is needed for transforming LiFePO 4 to NaFePO 4 to enable such a sustainable, green engineering path toward high-performance Na-ion batteries. Herein, we report on the development of a stable-cycling, sustainable olivine iron phosphate-based Na-ion battery empowered by an improved understanding of materials transformation and electrolyte chemistry. First, we found that the conventional carbonate electrolyte with fluoroethylene carbonate additive causes an additional plateau (~2.4 V) at the end of the discharge process of the FePO 4 ||Na metal cell, leading to lower initial discharge capacity and voltage. This result shows that the voltage profile is influenced by not only intrinsic materials phase transformation during battery cycling but also the electrolyte additives and interphases formed. With the 1 M NaPF 6 diglyme electrolyte, we achieved an excellent capacity retention of 96% and 98% after 500 cycles at 1 and 5 C, respectively. Second, we chemically sodiated FePO 4 to form single-phase Na 0.9 FePO 4 . Na 0.9 FePO 4 ||hard carbon full cells demonstrated a remarkable capacity retention of ~84% at 3 and 5 C after 1000 cycles. The successful implementation of hard carbon, which can be derived from biomass waste, will further improve the sustainability of energy storage technologies. Our research demonstrates that electrolyte chemistry influences the voltage profile of phase-changing electrodes and provides effective electrolyte and full-cell design solutions for stable-cycling NaFePO 4 .

36 MATERIALS SCIENCE↗
DOE OSTI2025

Excited electronic states of Na 2 and K 2 : The potential for long-lived “reservoir” states leading to collision induced population inversions

Potential energy curves (PECs) for the spin-free (ΛS) and spin–orbit (Ω) states associated with the four lowest-lying dissociation channels of Na 2 and K 2 were calculated at the SA-CASSCF/SO-CASPT2/aug-cc-pwCVQZ-DK level. The PECs of Na 2 were consistent with the experimental data and with the FS-CCSD (2,0) calculations, reproducing the double-well and the “shelf” character for some of the potentials of the excited states. For K 2 , the PECs behaved in a similar way and the spectroscopic parameters for the ground and the excited states are in good agreement with the available experimental values. The dissociation energy of K 2 was predicted to be D e = 4454 cm −1 , within an agreement of 5 cm −1 with the experiments. For Na 2 , D e = 5789 cm −1 compared to the experimental value of 6022 cm −1 . The inclusion of spin–orbit coupling effects resulted in avoided crossings, which affect the PECs. Spin–orbit changes the predicted curves for some excited Ω states arising from ΛS states that overlap each other, affecting their associated vibrational frequencies and bond distances. Here, the current studies of the low-lying states in K 2 reveal a similar structure to those of Na 2 , which suggests the accessibility of long-lived energy storing reservoir states and possible population inversions in K 2 following prior experimental work on the reaction of halogen atoms with Na 3 to produce excited states of Na 2 .

Ab-initio methods↗
DOE OSTI2023

Structure of amorphous materials in the NASICON system Na 1+x Ti 2 Si x P 3−x O 12

Abstract The structure of glasses in the sodium (Na) super-ionic conductor (NASICON) system Na 1 + x Ti 2 Si x P 3 − x O 12 with x = 0.8 and x = 1.0 was explored by combining neutron and high-energy x-ray diffraction with 29 Si, 31 P and 23 Na solid-state nuclear magnetic resonance (NMR) spectroscopy. The 29 Si magic angle spinning (MAS) NMR spectra reveal that the silica component remains fully polymerized in the form of Si 4 units, i.e. the silicon atoms are bound to four bridging oxygen atoms. The 31 P{ 23 Na} rotational echo adiabatic passage double resonance (REAPDOR) NMR data suggest that the 31 P MAS NMR line shape originates from four-coordinated P n units, where n = 1, 2 or 3 is the number of bridging oxygen atoms per phosphorus atom. These sites differ in their 31 P- 23 Na dipolar coupling strengths. The results support an intermediate range order scenario of a phosphosilicate mixed network-former glass in which the phosphate groups selectively attract the Na + modifier ions. Titanium takes a sub-octahedral coordination environment with a mean Ti–O coordination number of 5.17(4) for x = 0.8 and 4.86(4) for x = 1.0. A mismatch between the P–O and Si–O bond lengths of 8% is likely to inhibit the incorporation of silicon into the phosphorus sites of the NASICON crystal structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Ground state in proximity to a possible Kitaev spin liquid: The undistorted honeycomb iridate Na x IrO 3 (0.60 ≤ x ≤ 0.80)

Here, we report the results of our study of a recently synthesized honeycomb iridate Na x IrO 3 (0.60 ≤ x ≤ 0.80). Single-crystal Na x IrO 3 adopts a honeycomb lattice noticeably without distortions and stacking disorder inherently existent in its sister compound Na 2 IrO 3 . The oxidation state of the Ir ion is a mixed valence state resulting from a majority Ir 5+ (5d 4 ) ion and a minority Ir 6+ (5d 3 ) ion. Na x IrO 3 is a Mott insulator likely with a predominant pseudospin =1 state. It exhibits an effective moment of 1.1 μB/Ir and a Curie-Weiss temperature of –19 K but with no discernible long-range order above 1 K. The physical behavior below 1 K features two prominent anomalies at T h = 0.9 K and T l = 0.12 K in both the heat capacity and AC magnetic susceptibility. Intermediate between T h and T l lies a pronounced temperature linearity of the heat capacity with a large slope of 77 mJ /mole K 2 , a feature expected for highly correlated metals but not at all for insulators. These results along with a comparison drawn with the honeycomb lattices Na 2 IrO 3 and (Na 0.2 Li 0.8 ) 2 IrO 3 point to an exotic ground state in proximity to a possible Kitaev spin liquid.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Low-energy 23 Al β-delayed proton decay and 22 Na destruction in novae

The radionuclide 22 Na is a target of γ-ray astronomy searches, predicted to be produced during thermonuclear runaways driving classical novae. The 22 Na (p, γ) 23 Mg reaction is the main destruction channel of 22 Na during a nova, hence, its rate is needed to accurately predict the 22 Na yield. However, experimental determinations of the resonance strengths have led to inconsistent results. In this Rapid Communication, we report a measurement of the branching ratios of the 23 Al β-delayed protons as a probe of the key 204-keV (center-of-mass) 22 Na (p, γ) 23 Mg resonance strength. We report a factor of 5 lower branching ratio compared to the most recent literature value. The variation in 22 Na yield due to nuclear data inconsistencies was assessed using a series of hydrodynamic nova outburst simulations and has increased to a factor of 3.8, corresponding to a factor of ≈ 2 uncertainty in the maximum detectability distance. Finally, this is the first reported scientific measurement using the Gaseous Detector with Germanium Tagging system.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Searching for resonance states in Ne 22 ( p , γ ) Na 23

Globular clusters show strong correlations between different elements, such as the well-known sodium-oxygen anticorrelation. One of the main sources of uncertainty in this anticorrelation is the 22 Ne(p,γ) 23 Na reaction rate, due to the possible influence of an unobserved resonance state at E x = 8862 keV (E r,c.m. =68 keV). The influence of two higher-lying resonance states at E x = 8894 and 9000 keV has already been ruled out by direct 22 Ne(p,γ) 23 Na measurements. To study excited states in 23 Na above the proton threshold to determine if the unconfirmed resonance states in 23 Na exist. The non-selective proton inelastic scattering reaction at low energies was used to search for excited states in 23 Na above the proton threshold. Protons scattered from various targets were momentum-analysed in the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratorium, Munich, Germany. The resonance states previously reported at E x = 8862, 8894 and 9000 keV in other experiments were not observed in the present experiment at any angle. This result, combined with other non-observations of these resonance states in most other experiments, results in a strong presumption against the existence of these resonance states. Here, the previously reported resonance states at E x = 8862, 8894 and 9000 keV are unlikely to exist and should be omitted from future evaluations of the 22 Ne(p,γ) 23 Na reaction rates. Indirect studies using low-energy proton inelastic scattering are a simple and yet exceptionally powerful tool in helping to constrain astrophysical reaction rates by providing non-selective information of the excited states of nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Persistence of collectivity in the low-lying states of 30,31 Na inside the 𝑁 = 20 island of inversion

Near the 𝛽-stability line, nuclei with magic numbers are expected to exhibit spherical ground states. However, mass measurements of neutron-rich nuclei near the 𝑁 = 20 island of inversion have indicated an excess in the binding energies. These results, together with subsequent spectroscopic studies and theoretical works, point to the structural evolution from normal configurations to intruder-deformed configurations characterized by particle-hole excitations across the shell gap. Despite evidence of intruder-dominant ground states for the 30,31 Na isotopes in the vicinity of 𝑁 = 20, a question remains as to whether the deformation persists into the ground-state bands beyond the first excited states. Here, in this work, we report on a heavy-ion inelastic scattering measurement performed with GRETINA, the TRIPLEX device, and the S800 spectrograph to study the low-lying excitations in neutron-rich 30,31 Na . The observed gamma rays for the (4 + ) → (3 + ), (3 + ) → 2$^+_{g.s.}$, and (4 + ) → 2$^+_{g.s.}$ decays in 30 Na and for the (7/2 + ) → (5/2 + ) and (5/2 + )→3/2$^+_{g.s.}$ decays in 31 Na were used to extract the reduced transition probabilities 𝐵⁡(𝐸⁢2↑). We report the first measurement of the 𝐵⁡(𝐸⁢2↑) between the 3/2$^+_{g.s.}$ and the (7/2 + ) states in 31 Na . The results from this study are compared to shell-model calculations, confirming the persistence of large collectivity in the low-lying excited states consistent with the formation of the well-deformed ground-state bands in 30,31 Na .

collective models↗
DOE OSTI2024

Multiscale approaches for optimizing the impact of strain on Na-ion battery cycle life

Abstract The high costs and geopolitical challenges inherent to the lithium-ion (Li-ion) battery supply chain have driven a rising interest in the development of sodium-ion (Na-ion) batteries as a potential alternative. Unfortunately, the larger ionic radius of Na limits the reversibility of cycling because of the extensive atomic rearrangements that accompany Na-ion insertion, which in turn limit diffusion and charging speed, and lead to rapid degradation of the electrodes. The Center for Strain Optimization for Renewable Energy (STORE) was established to address these challenges and develop new electrode materials for Na-ion cells. This article discusses the current state-of-the-art materials used in Na-ion cells and several directions that STORE believes are critical to understand and control the structural and volumetric changes during the reversible (de)insertion of large cations. Graphical abstract Highlights Understanding the fundamental way materials respond to localized strains at the atomic length-scale is a critical first step in the development of highly reversible, long cycle life, Na-ion insertion hosts. This perspective explores a variety of methods that can be employed to mitigate the detrimental effects of large strain. The insights gained from these investigations should help lay the foundation for the creation of more economical and sustainable batteries that could have immediate impact on global energy infrastructure. Discussion Although there is near universal agreement that electrochemical energy storage must be an integral part of a green-energy future, there is less agreement about how to reduce the cost of energy storage. Replacing high-cost lithium-ion cells with lower-cost sodium-ion batteries is one option frequently considered in future energy models, but the details of what can be achieve with optimized sodium cell performance remains unclear. Here we posit that developing methods to mitigating strain on the electrode particle length scale is a key factor for achieving long-cycle-life sodium-ion batteries. Mitigating strain on the atomic scale suppress electrode-level volume change. Allowing for fast cycling in materials without the problems of electrode cracking or delamination. We further posit that understanding volume change in sodium-ion electrodes at a fundamental level will lead to the designing new sodium-ion electrode materials that will allow for efficient, stable, lower-cost energy storage.

Brady, Michael J.↗
DOE OSTI2022

Conversion Kinetics and Ionic Conductivity in Na-β”-Alumina + YSZ (Naβ”AY) Sodium Solid Electrolyte via Vapor Phase Conversion Process

Sodium ion batteries have been receiving increasing attention and may see potential revival in the near future, particularly in large-scale grid energy storage coupling with wind and solar power generation, due to the abundant sodium resources, low cost, and sufficiently high energy density. Among the known sodium ion conductors, the Na-β”-alumina electrolyte remains highly attractive because of its high ionic conductivity. This study focuses on the vapor phase synthesis of a Na-β”-Alumina + YSZ (Naβ”AY) composite sodium electrolyte, which has higher mechanical strength and stability than conventional single phase β”-Alumina. The objectives are the measurement of conversion kinetics through a newly developed weight-gain based model and the determination of sodium ionic conductivity in the composite electrolyte. Starting samples contained ~70 vol% α-Alumina and ~30 vol% YSZ (3 mol% Y 2 O 3 stabilized Zirconia) with and without a thin alumina surface layer made by sintering in air at 1600 °C. The sintered samples were placed in a powder of Na-β”-alumina and heat-treated at 1250 °C for various periods. Sample dimensions and weight were measured as a function of heat treatment time. The conversion of α-Alumina in the α-Alumina + YSZ composite into Naβ”AY occurred by coupled diffusion of sodium ions through Na-β”-alumina and of oxygen ions through YSZ, effectively diffusing Na2O. From the analysis of the time dependence of sample mass and dimensions, the effective diffusion coefficient of Na 2 O through the sample, D eff , was estimated to be 1.74 x 10 -7 cm2 s -1 , and the effective interface transfer parameter, k eff , was estimated as 2.33 x 10 -6 cm s -1 . By depositing a thin alumina coating layer on top of the bulk composite, the chemical diffusion coefficient of oxygen through single phase Na-β”-alumina was estimated as 4.35 x 10 -10 cm 2 s -1 . An AC impedance measurement was performed on a fully converted Naβ”AY composite, and the conductivity of the composite electrolyte was 1.3 x 10 -1 S cm -1 at 300 °C and 1.6 x 10 -3 S cm -1 at 25 °C, indicating promising applications in solid state or molten salt batteries at low to intermediate temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(Pr2Se3)4 by Materials Project

Na(Pr2Se3)4 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. Na is bonded to eight Se atoms to form distorted NaSe8 hexagonal bipyramids that share corners with eight equivalent PrSe8 hexagonal bipyramids, edges with four equivalent PrSe8 hexagonal bipyramids, and faces with eight PrSe8 hexagonal bipyramids. There are four shorter (3.05 Å) and four longer (3.29 Å) Na–Se bond lengths. There are three inequivalent Pr sites. In the first Pr site, Pr is bonded to eight Se atoms to form distorted PrSe8 hexagonal bipyramids that share corners with two equivalent NaSe8 hexagonal bipyramids, corners with six PrSe8 hexagonal bipyramids, edges with four PrSe8 hexagonal bipyramids, a faceface with one NaSe8 hexagonal bipyramid, and faces with seven PrSe8 hexagonal bipyramids. There are a spread of Pr–Se bond distances ranging from 3.00–3.25 Å. In the second Pr site, Pr is bonded to eight Se atoms to form distorted PrSe8 hexagonal bipyramids that share corners with eight PrSe8 hexagonal bipyramids, edges with two equivalent NaSe8 hexagonal bipyramids, edges with two equivalent PrSe8 hexagonal bipyramids, and faces with eight PrSe8 hexagonal bipyramids. There are a spread of Pr–Se bond distances ranging from 3.01–3.22 Å. In the third Pr site, Pr is bonded to eight Se atoms to form distorted PrSe8 hexagonal bipyramids that share corners with eight PrSe8 hexagonal bipyramids, edges with four PrSe8 hexagonal bipyramids, faces with two equivalent NaSe8 hexagonal bipyramids, and faces with six PrSe8 hexagonal bipyramids. There are a spread of Pr–Se bond distances ranging from 3.03–3.25 Å. There are three inequivalent Se sites. In the first Se site, Se is bonded to one Na and five Pr atoms to form a mixture of distorted edge, face, and corner-sharing SeNaPr5 octahedra. The corner-sharing octahedra tilt angles range from 14–52°. In the second Se site, Se is bonded to one Na and five Pr atoms to form a mixture of distorted edge, face, and corner-sharing SeNaPr5 octahedra. The corner-sharing octahedra tilt angles range from 19–50°. In the third Se site, Se is bonded to six Pr atoms to form a mixture of distorted edge, face, and corner-sharing SePr6 octahedra. The corner-sharing octahedra tilt angles range from 16–52°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(CO)2 by Materials Project

Na(CO)2 is Ullmanite-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Na is bonded to six O atoms to form a mixture of distorted edge and corner-sharing NaO6 octahedra. The corner-sharing octahedra tilt angles range from 61–70°. There are a spread of Na–O bond distances ranging from 2.36–2.82 Å. There are two inequivalent C sites. In the first C site, C is bonded in a distorted single-bond geometry to one O atom. The C–O bond length is 1.26 Å. In the second C site, C is bonded in a distorted single-bond geometry to one O atom. The C–O bond length is 1.27 Å. There are two inequivalent O sites. In the first O site, O is bonded in a 1-coordinate geometry to three equivalent Na and one C atom. In the second O site, O is bonded to three equivalent Na and one C atom to form a mixture of distorted edge and corner-sharing ONa3C trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(Ce2Se3)4 by Materials Project

Na(Ce2Se3)4 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. Na is bonded to eight Se atoms to form distorted NaSe8 hexagonal bipyramids that share corners with eight equivalent CeSe8 hexagonal bipyramids, edges with four equivalent CeSe8 hexagonal bipyramids, and faces with eight CeSe8 hexagonal bipyramids. There are four shorter (3.03 Å) and four longer (3.27 Å) Na–Se bond lengths. There are three inequivalent Ce sites. In the first Ce site, Ce is bonded to eight Se atoms to form distorted CeSe8 hexagonal bipyramids that share corners with two equivalent NaSe8 hexagonal bipyramids, corners with six CeSe8 hexagonal bipyramids, edges with four CeSe8 hexagonal bipyramids, a faceface with one NaSe8 hexagonal bipyramid, and faces with seven CeSe8 hexagonal bipyramids. There are a spread of Ce–Se bond distances ranging from 2.98–3.22 Å. In the second Ce site, Ce is bonded to eight Se atoms to form distorted CeSe8 hexagonal bipyramids that share corners with eight CeSe8 hexagonal bipyramids, edges with two equivalent NaSe8 hexagonal bipyramids, edges with two equivalent CeSe8 hexagonal bipyramids, and faces with eight CeSe8 hexagonal bipyramids. There are a spread of Ce–Se bond distances ranging from 2.98–3.17 Å. In the third Ce site, Ce is bonded to eight Se atoms to form distorted CeSe8 hexagonal bipyramids that share corners with eight CeSe8 hexagonal bipyramids, edges with four CeSe8 hexagonal bipyramids, faces with two equivalent NaSe8 hexagonal bipyramids, and faces with six CeSe8 hexagonal bipyramids. There are a spread of Ce–Se bond distances ranging from 3.01–3.20 Å. There are three inequivalent Se sites. In the first Se site, Se is bonded to six Ce atoms to form a mixture of distorted face, edge, and corner-sharing SeCe6 octahedra. The corner-sharing octahedra tilt angles range from 15–51°. In the second Se site, Se is bonded to one Na and five Ce atoms to form a mixture of distorted face, edge, and corner-sharing SeNaCe5 octahedra. The corner-sharing octahedra tilt angles range from 19–50°. In the third Se site, Se is bonded to one Na and five Ce atoms to form a mixture of distorted face, edge, and corner-sharing SeNaCe5 octahedra. The corner-sharing octahedra tilt angles range from 15–51°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(FeO2)2 by Materials Project

Na(FeO2)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Na is bonded in a 6-coordinate geometry to six O atoms. There are four shorter (2.42 Å) and two longer (2.53 Å) Na–O bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form edge-sharing FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.91–2.13 Å. In the second Fe site, Fe is bonded to six O atoms to form edge-sharing FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.03–2.08 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted rectangular see-saw-like geometry to one Na and three Fe atoms. In the second O site, O is bonded to two equivalent Na and three Fe atoms to form a mixture of distorted corner and edge-sharing ONa2Fe3 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(SiO4)2 by Materials Project

Na(SiO4)2 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Na is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Na–O bond distances ranging from 2.46–2.78 Å. Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.68 Å. There are five inequivalent O sites. In the first O site, O is bonded in a distorted T-shaped geometry to two equivalent Na and one O atom. The O–O bond length is 1.39 Å. In the second O site, O is bonded in a linear geometry to two equivalent Na atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the fifth O site, O is bonded in a distorted single-bond geometry to one Si and one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na by Materials Project

Na is Magnesium structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Na is bonded to twelve equivalent Na atoms to form a mixture of edge, face, and corner-sharing NaNa12 cuboctahedra. There are six shorter (3.73 Å) and six longer (3.76 Å) Na–Na bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na by Materials Project

Na is Tungsten structured and crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Na is bonded in a body-centered cubic geometry to eight equivalent Na atoms. All Na–Na bond lengths are 3.61 Å.

36 MATERIALS SCIENCE↗