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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Additives for lithium batteries and methods

Lithium tetrafluoro(malonato)phosphate compounds are useful as additives in lithium ion battery applications. The compounds are represented by Formula (I): MPF 4 [—O(C═O)—(CX′X″)—(C═O)O—]; wherein M is Li or Na; each X′ and X″ independently is selected from the group consisting of H, alkyl, fluoro-substituted alkyl, and F; or wherein the X′ and X″ together are —CR 2 —(CR′ 2 ) m —CR″ 2 —; each R, R′ and R″ independently is selected from the group consisting of H methyl, trifluoromethyl, and F; and in is 0 or 1. These compounds can be prepared in high purity and a high yield by reaction of a metal hexafluorophosphate with a bis-silyl malonate compound. A similar oxalato compound, lithium tetrafluoro(oxalato)phosphate), can be made in the same manner, but using a bis-silyl oxalate in place of the bis-silyl malonate. Advantageously, the compounds can be formed, in situ, in a LiPF 6 -containing electrolyte solution.

Liao, Chen↗
DOE OSTI2022

Size Dependent Optical Properties and Structure of ZnS Nanocrystals Prepared from a Library of Thioureas

Here, ZnS nanocrystals (λ max (1S e -1S 3/2h ) = 260 - 320 nm, d = 1.7 - 10.0 nm) are synthesized from Zn(O 2 CR) 2 (O 2 CR = tetra-decanoate, oleate and 2-hexyldecanoate), N,N'-disubstituted and N,N',N'-trisubstituted thioureas, and P,P,N-trisubstituted phos-phanecarbothioamides. The influence of precursor substitution, ligand sterics, and reaction temperature on the final nanocrystal size were evaluated. By using saturated hydrocarbon solvents and saturated aliphatic carboxylate ligands, polymeric byproducts could be avoided and pure ZnS nanocrystals isolated. Elevated temperatures, slower precursor conversion reactivity and branched zinc 2-hexyldecanoate yield the largest ZnS nanocrystals. Carefully purified zinc carboxylate, rapidly converting precursors, and cooling the synthesis mixture following complete precursor conversion provide quasi spherical nanocrystals with the narrowest shape dispersity. Nanocrystal sizes were measured using pair distribution function (PDF) analysis of X-ray scattering and scanning transmission electron microscopy (STEM) and plotted versus the energy of their first excitonic optical absorption. The resulting empirical relationship provides a useful method to characterize the nanocrystal size from 1.7-4.0 nm using optical absorption spectroscopy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Synthesis of Chromium(IV) Nitrides Through High-Spin Tetrahedral Chromium(I) Intermediates

Reduction of (depe) 2 CrCl 2 (depe = 1,2-bis- (diethylphosphino)ethane) and (dep-benz) 2 CrCl 2 (dep-benz = 1,2-bis(diethylphosphino)benzene) under 1 atm of N 2 furnished the dinitrogen complexes (depe) 2 Cr(N 2 ) 2 and (dep-benz) 2 Cr(N 2 ) 2 , respectively. One-electron oxidation of these products with FcBAr F 4 (Fc = ferrocenium, BAr F 4 = B(3,5-(CF 3 ) 2 C 6 H 3 ) 4 ) yielded the unusual, high-spin tetrahedral complexes [(depe) 2 Cr][BAr F 4 ] and [(dep-benz) 2 Cr][BAr F 4 ] with concomitant loss of dinitrogen. Reaction of the chromium(I) derivatives with Ph 3 CN 3 furnished rare examples of chromium(IV) nitrides as confirmed spectroscopically and by X-ray crystallography. While [(depe) 2 Cr(≡N)][BAr F 4 ] underwent association of isocyanides accompanied by partial ligand dissociation, neither chromium nitride was reactive toward H 2 or diphenylsilane under thermal or photochemical conditions. These results distinguish the unique properties of the chromium(IV) nitrides as compared to heavier group 6 congeners and demonstrate both the feasibility of nitride synthesis and the limitations of dinitrogen cleavage and subsequent N−H bond formation.

Chromium↗
DOE OSTI2020

Materials Data on KCrCdC6N6O by Materials Project

(K)2(Cr)2(Cd(CN)6)2O2 is Tungsten-derived structured and crystallizes in the cubic F-43m space group. The structure is zero-dimensional and consists of four chromium molecules, four potassium molecules, four water molecules, and four Cd(CN)6 clusters. In each Cd(CN)6 cluster, Cd2+ is bonded in an octahedral geometry to six equivalent N3- atoms. All Cd–N bond lengths are 2.34 Å. C+2.33+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a linear geometry to one Cd2+ and one C+2.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Inverse Lieb materials: altermagnetism and more

The Lieb lattice, originally proposed for cuprate superconductors, has gained new attention in the emerging field of altermagnetism as a minimal analytical model for the latter. While the inverse Lieb lattice (ILL) was once considered purely theoretical, several materials with this motif have recently been discovered. Its unique geometry supports complex magnetic orders driven by geometric frustration, offering high tunability. In this work, we provide comprehensive insights into ILL magnetic phases and establish guidelines for identifying altermagnets. Using a Heisenberg model, we first construct phase diagrams to elucidate the mechanisms underlying experimental magnetic phases. We then bridge theory and experiment via density functional theory (DFT) calculations on existing ILL compounds, finding results consistent with experimental data. Notably, we identified a trend linking d-shell filling to magnetic order, where d x (x≤5) configurations show a propensity for altermagnetism. We also highlight Sr 2 CrO 2 Cr 2 OAs 2 as a promising metallic altermagnet with highly anisotropic J 2 exchange and a high Néel temperature (~600 K). Finally, our magnon spectra calculations confirm that chiral splittings correlate directly with anisotropies between inequivalent J 2 interactions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Identification of key oxidative intermediates and the function of chromium dopants in PKU-8: catalytic dehydrogenation of sec-alcohols with tert-butylhydroperoxide

Catalytic oxidation using green oxidants has played an important role in modern chemical engineering, however the in-situ generated active groups and the related catalytic mechanism need to be further understood. Combined with several measurements, such as isotopic tracers, molecular probes and cycle voltammetry, chromium ions were observed to undergo a Cr 3+ –Cr 2+ –Cr 3+ redox cycle. Simultaneously, t-BuOO* groups are generated in a large quantity and seem to function as the most critical active species to enhance the dehydrogenation of sec-alcohols when using TBHP as oxidant. DFT calculations give an energetically favorable pathway for TBHP activation, agreeing well with the obtained catalytic results. Here, a reaction scheme was finally proposed to interpret the probable mechanistic process.

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

Insights on the corrosion thermodynamics of chromium in molten LiF-NaF-KF eutectic salts

The thermodynamic stability of chromium in the Cr 0 , Cr 2+ , and Cr 3+ oxidation states considering various F - ion coordination compounds was investigated in molten LiF–NaF-KF (FLiNaK) eutectic salt. Potential fluoride ion activity (F - and CrF 3 - ) diagrams were constructed to predict the most stable Cr oxidation states as a function of anion activity, solvation state of chromium ions and potential at 600 °C. The Gibbs free energies of these compounds were estimated by utilizing a combined cyclic voltammetry – Nernst theory analysis approach in FLiNaK salt. To verify the constructed diagrams, X-ray diffraction was utilized after exposure of Cr at various applied potentials to determine whether compounds detected in solidified FLiNaK salts agreed with thermodynamic calculations. This work aims to identify key thermodynamic factors that are significant to chromium corrosion for molten salt nuclear reactor applications. The F - stability region spans the entire region where spontaneous corrosion of Cr occurs. Cr may be oxidized to Cr 2+ and Cr 3+ in the presence HF (due to moisture as an impurity) spontaneously except some conditions of p 1/2 H 2 /a HF etc. This situation is not changed qualitatively for various states of solvation between oxidized Cr solute in F - solvent and this aspect is substantially similar for the two cases (pair 1: Cr 0 /CrF 3 - / CrF 6 3- ; pair 2: Cr 0 /CrF 4 2- /CrF 5 2- ) considered in this work.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesis and Electronic Structure of Anionic 1,1'-diphosphametallocenes of Chromium and Iron

In this work, we report two anionic diphosphametallocenates, [K(2.2.2-crypt)][M(PC 4 Me 4 ) 2 ] (M = Cr, 2-Cr ; Fe, 2-Fe ). Both are low-spin ( S = ½) by EPR spectroscopy and SQUID magnetometry. This contrasts the high-spin ( S = ) ferrocenate, [K(2.2.2-crypt)][Fe(C 5 H 2 -1,2,4- t Bu) 2 ] ( 4-Fe ). Quantum chemical calculations suggest this is due to significant differences in ligand field splitting of the d-orbitals which also explain structural features in the 2-M complexes.

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

Effect of Ni deposition on CrI 3 monolayer: First-principles study

In our recent experimental work, we demonstrated that Ni thin film deposition can be used to tune the surface magnetic states in bulk CrI 3 . Here, we present the results of a computational study of Ni deposition on a CrI 3 monolayer. In particular, we compare structural, electronic, and magnetic properties of three different systems: a pristine CrI 3 monolayer, a CrI 3 monolayer with partial Ni coverage, and a CrI 3 monolayer with full Ni coverage. The corresponding cells used in our calculations are Cr 2 I 6 , Cr 2 I 6 Ni 1 , and Cr 2 I 6 Ni 3 . In Cr 2 I 6 Ni 1 , the Ni atom is positioned over the hollow site, which corresponds to the lowest energy configuration. In Cr 2 I 6 Ni 3 , the three Ni atoms are positioned over the single hollow site, and over the two Cr sites. Our calculations indicate that the partial coverage of CrI 3 monolayer with Ni retains the semiconducting nature of the parent compound, but results in a strong reduction of the energy band gap. At the same time, the full coverage of CrI 3 monolayer with Ni results in a metallic transition, with a highly spin-polarized (possibly half-metallic) electronic structure. The magnetic alignment of the CrI 3 monolayer with the deposited Ni is ferrimagnetic, due to the anti-aligned magnetic moments of Cr and Ni atoms. While the partial coverage of the CrI 3 monolayer with Ni has a moderate impact on the lattice parameter of the parent compound, full coverage by Ni results in a significant increase of the lattice constant. For both partial and full coverages, the lowest energy configuration corresponds to the Ni atoms being approximately aligned with the out-of-plane coordinate of the surface iodine layer. In addition, in the full coverage mode, the Cr layer exhibits a significant shift away from the Ni atoms, effectively “detaching” the Ni / I atomic layer from the rest of the cell.

2D magnetism↗
DOE OSTI2020

Materials Data on Cr(C5O2)2 by Materials Project

Cr(CO2)2(C)8 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of thirty-two methane molecules and one Cr(CO2)2 ribbon oriented in the (1, 0, 0) direction. In the Cr(CO2)2 ribbon, there are two inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded to five O2- atoms to form distorted edge-sharing CrO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 2.04–2.32 Å. In the second Cr2+ site, Cr2+ is bonded to five O2- atoms to form distorted edge-sharing CrO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 2.03–2.33 Å. There are four inequivalent C+0.60+ sites. In the first C+0.60+ site, C+0.60+ is bonded in a bent 120 degrees geometry to two O2- atoms. Both C–O bond lengths are 1.27 Å. In the second C+0.60+ site, C+0.60+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.26 Å) and one longer (1.29 Å) C–O bond length. In the third C+0.60+ site, C+0.60+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.26 Å) and one longer (1.29 Å) C–O bond length. In the fourth C+0.60+ site, C+0.60+ is bonded in a bent 120 degrees geometry to two O2- atoms. Both C–O bond lengths are 1.27 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr2+ and one C+0.60+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cr2+ and one C+0.60+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr2+ and one C+0.60+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr2+ and one C+0.60+ atom. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr2+ and one C+0.60+ atom. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr2+ and one C+0.60+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cr2+ and one C+0.60+ atom. In the eighth O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr2+ and one C+0.60+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(GaS2)2 by Materials Project

Cr(GaS2)2 crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of one Cr(GaS2)2 sheet oriented in the (0, 0, 1) direction. Cr2+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with six GaS4 tetrahedra and edges with six equivalent CrS6 octahedra. There are four shorter (2.47 Å) and two longer (2.49 Å) Cr–S bond lengths. There are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three equivalent CrS6 octahedra and corners with six equivalent GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are a spread of Ga–S bond distances ranging from 2.29–2.36 Å. In the second Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three equivalent CrS6 octahedra and corners with six equivalent GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are a spread of Ga–S bond distances ranging from 2.29–2.36 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to three equivalent Cr2+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SCr3Ga trigonal pyramids. In the second S2- site, S2- is bonded to three equivalent Cr2+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SCr3Ga trigonal pyramids. In the third S2- site, S2- is bonded in a trigonal non-coplanar geometry to three equivalent Ga3+ atoms. In the fourth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three equivalent Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(ClO2)2 by Materials Project

Cr(O2Cl)2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of two Cr(O2Cl)2 ribbons oriented in the (1, 0, 0) direction. Cr is bonded in a distorted octahedral geometry to four O and two equivalent Cl atoms. There is two shorter (1.67 Å) and two longer (1.90 Å) Cr–O bond length. Both Cr–Cl bond lengths are 2.48 Å. There are two inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one Cr and one Cl atom. The O–Cl bond length is 1.66 Å. In the second O site, O is bonded in a single-bond geometry to one Cr atom. Cl is bonded in a water-like geometry to one Cr and one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(PO4)2 by Materials Project

Cr(PO4)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two Cr(PO4)2 sheets oriented in the (0, 0, 1) direction. Cr6+ is bonded to six O2- atoms to form distorted CrO6 octahedra that share corners with five PO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.59–2.15 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent CrO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 27–55°. There are a spread of P–O bond distances ranging from 1.52–1.62 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–48°. There are a spread of P–O bond distances ranging from 1.52–1.62 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr6+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr6+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Cr6+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr6+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the eighth O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr6+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Medium-Entropy Engineering of Magnetism in Layered Antiferromagnet Cu x Ni 2(1- x ) Cr x P 2 S 6

Antiferromagnetic van der Waals-type M 2 P 2 X 6 compounds provide a versatile material platform for studying 2D magnetism and relevant phenomena. Establishing ferromagnetism in 2D materials is technologically valuable. Though magnetism is generally tunable via a chemical way, it is challenging to induce ferromagnetism with isovalent chalcogen and bimetallic substitutions in M 2 P 2 X 6 . Here, we report co-substitution of Cu 1+ and Cr 3+ for Ni 2+ in Ni 2 P 2 S 6 , creating Cu x Ni 2(1-x) Cr x P 2 S 6 medium-entropy alloys spanning a full substitution range (x = 0 to 1). Such substitution strategy leads to a unique evolution in crystal structure and magnetic phases that are distinct from traditional isovalent bimetallic doping, with Cu and Cr co-substitution enhancing ferromagnetic correlations and generating a weak ferromagnetic phase in intermediate compositions. This aliovalent substitution strategy offers a universal approach for tuning layered magnetism in antiferromagnetic systems, which along with the potential for light-matter interaction and high-temperature ferroelectricity, can enable multifunctional device applications.

2D magnetism↗
DOE OSTI2021

Computational Spectroscopy of the Cr–Cr Bond in Coordination Complexes

In this work, we report the accurate computational vibrational analysis of the Cr–Cr bond in dichromium complexes using second-order multireference complete active space methods (CASPT2), allowing direct comparison with experimental spectroscopic data both to facilitate interpreting the low-energy region of the spectra and to provide insights into the nature of the bonds themselves. Recent technological development by the authors has realized such computation for the first time. Accurate simulation of the vibrational structure of these compounds has been hampered by their notorious multiconfigurational electronic structure that yields bond distances that do not correlate with bond order. Some measured Cr–Cr vibrational stretching modes, ν(Cr 2 ), have suggested weaker bonding, even for so-called ultrashort Cr–Cr bonds, while others are in line with the bond distance. Here, we optimize geometries and compute ν(Cr 2 ) with CASPT2 for three well-characterized complexes, Cr 2 (O 2 CCH 3 ) 4 (H 2 O) 2 , Cr 2 (mhp) 4 , and Cr 2 (dmp) 4 . We obtain CASPT2 harmonic ν(Cr 2 ) modes in good agreement with experiment at 282 cm –1 for Cr 2 (mhp) 4 and 353 cm –1 for Cr 2 (dmp) 4 , compute 50 Cr and 54 Cr isotope shifts, and demonstrate that the use of the so-called IPEA shift leads to improved Cr–Cr distances. Additionally, normal mode sampling was used to estimate anharmonicity along ν(Cr 2 ), leading to an anharmonic mode of 272 cm –1 for Cr 2 (mhp) 4 and 333 cm –1 for Cr 2 (dmp) 4 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(FeSe2)2 by Materials Project

Cr(FeSe2)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Cr3+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Cr–Se bond distances ranging from 2.45–2.51 Å. There are two inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded in a distorted pentagonal planar geometry to five Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.36–2.50 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded in a distorted pentagonal planar geometry to five Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.35–2.57 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to one Cr3+ and two Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded to one Cr3+ and three Fe+2.50+ atoms to form a mixture of distorted edge and corner-sharing SeCrFe3 tetrahedra. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to one Cr3+ and two Fe+2.50+ atoms. In the fourth Se2- site, Se2- is bonded to one Cr3+ and three Fe+2.50+ atoms to form a mixture of distorted edge and corner-sharing SeCrFe3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(GeO3)2 by Materials Project

Cr(GeO3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six equivalent GeO4 tetrahedra and edges with two equivalent CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.85–2.08 Å. Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent CrO6 octahedra and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–60°. There are a spread of Ge–O bond distances ranging from 1.75–1.79 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ge4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr4+ and one Ge4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cr4+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗