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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Crystal Structures, Optical Behavior, and Magnetic Properties in Hydrated Lanthanide Iron Sulfates

Single crystals of LnFe(SO 4 ) 3 (H 2 O) 2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm; compounds 1–11) and LnFe(SO 4 ) 3 (H 2 O) (Ln = Tm, Yb, Lu; compounds 12–14) were synthesized under hydrothermal conditions. Single-crystal X-ray diffraction (SCXRD) analysis revealed that the dihydrated compounds (1–11) crystallize in centrosymmetric (CS) structures, with the lanthanide ions adopting eight-coordinate geometries. In contrast, the monohydrated compounds (12–14) exhibit noncentrosymmetric (NCS) structures, where the lanthanide ions are seven-coordinated. Vibrating sample magnetometry (VSM) confirmed that compounds 2, 4, and 7–11 are paramagnetic below 400 K, with compound 8 displaying the highest magnetic susceptibility. Compounds 1, 5, 6, 13, and 14 show a sharp increase in magnetic susceptibility at Néel temperatures ( T N ) of approximately 72, 76, 70, 58, and 56 K, respectively, indicating antiferromagnetic ordering. High-temperature magnetic susceptibility measurements further support the presence of antiferromagnetic transitions in these compounds. Second harmonic generation (SHG) measurements showed that the noncentrosymmetric Yb (compound 13) and Lu (compound 14) compounds exhibit SHG intensities of 0.3× and 1.6× that of potassium dihydrogen phosphate (KDP), respectively.

anions↗
DOE OSTI2020

Materials Data on Ho2(Ga3Co)3 by Materials Project

Ho2(CoGa3)3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ho is bonded in a 11-coordinate geometry to eleven Ga atoms. There are a spread of Ho–Ga bond distances ranging from 2.97–3.03 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to eight Ga atoms. There are a spread of Co–Ga bond distances ranging from 2.50–2.56 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to eight Ga atoms. There are four shorter (2.52 Å) and four longer (2.55 Å) Co–Ga bond lengths. There are four inequivalent Ga sites. In the first Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, three Co, and five Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.73–2.81 Å. In the second Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Ho, three Co, and five Ga atoms. There are one shorter (2.69 Å) and two longer (2.80 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Ho, two equivalent Co, and six Ga atoms. Both Ga–Ga bond lengths are 2.74 Å. In the fourth Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Ho, two equivalent Co, and six Ga atoms. The Ga–Ga bond length is 2.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Theoretical Design of Lithium Chloride Superionic Conductors for All-Solid-State High-Voltage Lithium-Ion Batteries

The development of solid electrolytes (SEs) is a promising pathway to improve the energy density and safety of conventional Li ion batteries. Several lithium chloride SEs, Li 3 MCl 6 (M = Y, Er, In, and Sc), have gained popularity due to their high ionic conductivity, wide electrochemical window, and good chemical stability. This study systematically investigated 17 Li 3 MCl 6 SEs to identify novel and promising lithium chloride SEs. Calculation results revealed that 12 Li 3 MCl 6 (M = Bi, Dy, Er, Ho, In, Lu, Sc, Sm, Tb, TI, Tm, and Y) were stable phase with a wide electrochemical stability window and excellent chemical stability against cathode materials and moisture. Li-ion transport properties were examined using bond valence site energy (BVSE) and ab initio molecular dynamics (AIMD) calculation. Li 3 MCl 6 showed the lower migration energy barrier in monoclinic structures, while orthorhombic and trigonal structures exhibited higher energy barriers due to the sluggish diffusion along the two-dimensional path based on the BVSE model. AIMD results confirmed the slower ion migration along the 2D path, exhibiting lower ionic diffusivity and higher activation energy in orthorhombic and trigonal structures. For the further increase of ionic conductivity in monoclinic structures, Li-ion vacancy was formed by the substitution of M 3+ with Zr 4+ . Zr-substituted phase (Li 2.5 M 0.5 Zr 0.5 Cl 6 , M = In, Sc) exhibited up to a fourfold increase in ionic conductivity. This finding suggested that the optimization of Li vacancy in the Li 3 MCl 6 SEs could lead to superionic Li 3 MCl 6 SEs.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on Ho4MnS7 by Materials Project

Ho4MnS7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Ho–S bond distances ranging from 2.71–3.05 Å. In the second Ho3+ site, Ho3+ is bonded to seven S2- atoms to form distorted HoS7 pentagonal bipyramids that share corners with two equivalent MnS6 octahedra, corners with six HoS6 octahedra, edges with four HoS6 octahedra, and faces with two equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 22–68°. There are a spread of Ho–S bond distances ranging from 2.69–2.98 Å. In the third Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share a cornercorner with one HoS6 octahedra, a cornercorner with one MnS6 octahedra, corners with two equivalent HoS7 pentagonal bipyramids, edges with two equivalent HoS6 octahedra, and edges with three equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Ho–S bond distances ranging from 2.66–2.72 Å. In the fourth Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share a cornercorner with one HoS6 octahedra, corners with two equivalent MnS6 octahedra, corners with four equivalent HoS7 pentagonal bipyramids, edges with two equivalent HoS6 octahedra, edges with three equivalent MnS6 octahedra, and an edgeedge with one HoS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–52°. There are a spread of Ho–S bond distances ranging from 2.67–2.77 Å. Mn2+ is bonded to six S2- atoms to form MnS6 octahedra that share corners with three HoS6 octahedra, corners with two equivalent HoS7 pentagonal bipyramids, edges with two equivalent MnS6 octahedra, and edges with three equivalent HoS6 octahedra. The corner-sharing octahedra tilt angles range from 3–55°. There are a spread of Mn–S bond distances ranging from 2.53–2.66 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded to four Ho3+ and one Mn2+ atom to form distorted SHo4Mn trigonal bipyramids that share corners with five SHo3Mn tetrahedra, corners with four SHo5 trigonal bipyramids, an edgeedge with one SHo4 tetrahedra, and edges with five SHo4Mn trigonal bipyramids. In the second S2- site, S2- is bonded to three Ho3+ and two equivalent Mn2+ atoms to form distorted SHo3Mn2 trigonal bipyramids that share corners with five SHo3Mn tetrahedra, corners with four SHo5 trigonal bipyramids, an edgeedge with one SHo3Mn tetrahedra, and edges with five SHo4Mn trigonal bipyramids. In the third S2- site, S2- is bonded to five Ho3+ atoms to form distorted SHo5 trigonal bipyramids that share corners with four equivalent SHo3Mn tetrahedra, corners with six SHo4Mn trigonal bipyramids, edges with three SHo3Mn tetrahedra, and edges with six SHo3Mn2 trigonal bipyramids. In the fourth S2- site, S2- is bonded to five Ho3+ atoms to form distorted SHo5 trigonal bipyramids that share corners with four equivalent SHo4 tetrahedra, corners with six SHo4Mn trigonal bipyramids, edges with three SHo3Mn tetrahedra, and edges with six SHo4Mn trigonal bipyramids. In the fifth S2- site, S2- is bonded to three Ho3+ and one Mn2+ atom to form distorted SHo3Mn tetrahedra that share corners with three SHo3Mn tetrahedra, corners with nine SHo4Mn trigonal bipyramids, and edges with four SHo3Mn2 trigonal bipyramids. In the sixth S2- site, S2- is bonded to four Ho3+ atoms to form distorted SHo4 tetrahedra that share corners with three SHo3Mn tetrahedra, corners with nine SHo4Mn trigonal bipyramids, and edges with four SHo4Mn trigonal bipyramids. In the seventh S2- site, S2- is bonded in a rectangular see-saw-like geometry to two equivalent Ho3+ and two equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho4CrS7 by Materials Project

Ho4CrS7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Ho–S bond distances ranging from 2.72–3.08 Å. In the second Ho3+ site, Ho3+ is bonded to seven S2- atoms to form distorted HoS7 pentagonal bipyramids that share corners with two equivalent CrS6 octahedra, corners with six HoS6 octahedra, edges with four HoS6 octahedra, and faces with two equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 21–69°. There are a spread of Ho–S bond distances ranging from 2.68–2.95 Å. In the third Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share a cornercorner with one HoS6 octahedra, a cornercorner with one CrS6 octahedra, corners with two equivalent HoS7 pentagonal bipyramids, edges with two equivalent HoS6 octahedra, and edges with three equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Ho–S bond distances ranging from 2.66–2.71 Å. In the fourth Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share a cornercorner with one HoS6 octahedra, corners with two equivalent CrS6 octahedra, corners with four equivalent HoS7 pentagonal bipyramids, edges with two equivalent HoS6 octahedra, edges with three equivalent CrS6 octahedra, and an edgeedge with one HoS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–50°. There are a spread of Ho–S bond distances ranging from 2.65–2.77 Å. Cr2+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with three HoS6 octahedra, corners with two equivalent HoS7 pentagonal bipyramids, edges with two equivalent CrS6 octahedra, and edges with three equivalent HoS6 octahedra. The corner-sharing octahedra tilt angles range from 3–54°. There are a spread of Cr–S bond distances ranging from 2.43–2.60 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded to four Ho3+ and one Cr2+ atom to form distorted SHo4Cr trigonal bipyramids that share corners with five SHo3Cr tetrahedra, corners with two equivalent SHo5 trigonal bipyramids, edges with two equivalent SHo3Cr2 square pyramids, an edgeedge with one SHo4 tetrahedra, and edges with two equivalent SHo4Cr trigonal bipyramids. In the second S2- site, S2- is bonded to three Ho3+ and two equivalent Cr2+ atoms to form distorted SHo3Cr2 square pyramids that share corners with five SHo3Cr tetrahedra, corners with two equivalent SHo5 trigonal bipyramids, edges with two equivalent SHo3Cr2 square pyramids, an edgeedge with one SHo3Cr tetrahedra, and edges with three SHo4Cr trigonal bipyramids. In the third S2- site, S2- is bonded to five Ho3+ atoms to form distorted SHo5 trigonal bipyramids that share corners with two equivalent SHo3Cr2 square pyramids, corners with four equivalent SHo3Cr tetrahedra, corners with two equivalent SHo4Cr trigonal bipyramids, an edgeedge with one SHo3Cr2 square pyramid, edges with three SHo3Cr tetrahedra, and edges with two equivalent SHo5 trigonal bipyramids. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to five Ho3+ atoms. In the fifth S2- site, S2- is bonded to three Ho3+ and one Cr2+ atom to form distorted SHo3Cr tetrahedra that share corners with four equivalent SHo3Cr2 square pyramids, corners with three SHo3Cr tetrahedra, corners with five SHo4Cr trigonal bipyramids, an edgeedge with one SHo3Cr2 square pyramid, and an edgeedge with one SHo5 trigonal bipyramid. In the sixth S2- site, S2- is bonded to four Ho3+ atoms to form distorted SHo4 tetrahedra that share a cornercorner with one SHo3Cr2 square pyramid, corners with three SHo3Cr tetrahedra, corners with four equivalent SHo4Cr trigonal bipyramids, and edges with three SHo4Cr trigonal bipyramids. In the seventh S2- site, S2- is bonded in a rectangular see-saw-like geometry to two equivalent Ho3+ and two equivalent Cr2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Insights into the Mechanism of Neptunium Oxidation to the Heptavalent State

Abstract Neptunium can exist in multiple oxidation states, including the rare and poorly understood heptavalent form. In this work, we monitored the formation of heptavalent neptunium [Np(VII)O 4 (OH) 2 ] 3− during ozonolysis of aqueous M OH ( M =Li, Na, K) solutions using a combined experimental and theoretical approach. All experimental reactions were closely monitored via absorption and vibrational spectroscopy to follow both the oxidation state and the speciation of neptunium guided by the calculated vibrational frequencies for various neptunium species. The mechanism of the reaction partly involves oxidative dissolution of transient Np(VI) oxide/hydroxide solid phases, the identity of which are dependent on the co‐precipitating counter‐cation Li + /Na + /K + . Additional calculations suggest that the most favorable energetic pathway occurs through the reaction of a [Np(V)O 2 (OH) 4 ] 3− with the hydroxide radical to form [Np(VI)O 2 (OH) 4 ] 2− , followed by an additional oxidation with HO⋅ to create [Np(VII)O 4 (OH) 2 ] 3− .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Ho4CdSe7 by Materials Project

Ho4CdSe7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to seven Se2- atoms to form distorted HoSe7 pentagonal bipyramids that share corners with four HoSe6 octahedra, corners with four equivalent CdSe6 octahedra, an edgeedge with one CdSe6 octahedra, edges with three equivalent HoSe6 octahedra, edges with two equivalent HoSe7 pentagonal bipyramids, and faces with two equivalent HoSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 22–69°. There are a spread of Ho–Se bond distances ranging from 2.84–3.18 Å. In the second Ho3+ site, Ho3+ is bonded to seven Se2- atoms to form distorted HoSe7 pentagonal bipyramids that share corners with two equivalent CdSe6 octahedra, corners with six HoSe6 octahedra, edges with four HoSe6 octahedra, edges with two equivalent HoSe7 pentagonal bipyramids, and faces with two equivalent HoSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 21–68°. There are a spread of Ho–Se bond distances ranging from 2.84–3.11 Å. In the third Ho3+ site, Ho3+ is bonded to six Se2- atoms to form HoSe6 octahedra that share a cornercorner with one HoSe6 octahedra, a cornercorner with one CdSe6 octahedra, corners with four HoSe7 pentagonal bipyramids, edges with two equivalent HoSe6 octahedra, and edges with six HoSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 54–56°. There are a spread of Ho–Se bond distances ranging from 2.79–2.87 Å. In the fourth Ho3+ site, Ho3+ is bonded to six Se2- atoms to form HoSe6 octahedra that share a cornercorner with one HoSe6 octahedra, corners with two equivalent CdSe6 octahedra, corners with six HoSe7 pentagonal bipyramids, edges with two equivalent HoSe6 octahedra, edges with three equivalent CdSe6 octahedra, and an edgeedge with one HoSe7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–54°. There are a spread of Ho–Se bond distances ranging from 2.77–2.91 Å. Cd2+ is bonded to six Se2- atoms to form CdSe6 octahedra that share corners with three HoSe6 octahedra, corners with six HoSe7 pentagonal bipyramids, edges with two equivalent CdSe6 octahedra, edges with three equivalent HoSe6 octahedra, and an edgeedge with one HoSe7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–56°. There are a spread of Cd–Se bond distances ranging from 2.77–2.89 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Ho3+ and one Cd2+ atom to form distorted SeHo4Cd trigonal bipyramids that share corners with five SeHo3Cd tetrahedra, corners with four SeHo5 trigonal bipyramids, an edgeedge with one SeHo4 tetrahedra, and edges with five SeHo4Cd trigonal bipyramids. In the second Se2- site, Se2- is bonded to three Ho3+ and two equivalent Cd2+ atoms to form distorted SeHo3Cd2 trigonal bipyramids that share corners with five SeHo3Cd tetrahedra, corners with four SeHo5 trigonal bipyramids, an edgeedge with one SeHo3Cd tetrahedra, and edges with five SeHo4Cd trigonal bipyramids. In the third Se2- site, Se2- is bonded to five Ho3+ atoms to form distorted SeHo5 trigonal bipyramids that share corners with four equivalent SeHo3Cd tetrahedra, corners with six SeHo4Cd trigonal bipyramids, edges with three SeHo3Cd tetrahedra, and edges with six SeHo3Cd2 trigonal bipyramids. In the fourth Se2- site, Se2- is bonded to five Ho3+ atoms to form distorted SeHo5 trigonal bipyramids that share corners with four equivalent SeHo4 tetrahedra, corners with six SeHo4Cd trigonal bipyramids, edges with three SeHo3Cd tetrahedra, and edges with six SeHo4Cd trigonal bipyramids. In the fifth Se2- site, Se2- is bonded to three Ho3+ and one Cd2+ atom to form distorted SeHo3Cd tetrahedra that share corners with three SeHo3Cd tetrahedra, corners with nine SeHo4Cd trigonal bipyramids, and edges with four SeHo3Cd2 trigonal bipyramids. In the sixth Se2- site, Se2- is bonded to four Ho3+ atoms to form distorted SeHo4 tetrahedra that share corners with three SeHo3Cd tetrahedra, corners with nine SeHo4Cd trigonal bipyramids, and edges with four SeHo4Cd trigonal bipyramids. In the seventh Se2- site, Se2- is bonded in a square co-planar geometry to two equivalent Ho3+ and two equivalent Cd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho4CdS7 by Materials Project

Ho4CdS7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to seven S2- atoms to form distorted HoS7 pentagonal bipyramids that share corners with four HoS6 octahedra, corners with four equivalent CdS6 octahedra, an edgeedge with one CdS6 octahedra, edges with three equivalent HoS6 octahedra, edges with two equivalent HoS7 pentagonal bipyramids, and faces with two equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 22–70°. There are a spread of Ho–S bond distances ranging from 2.71–3.04 Å. In the second Ho3+ site, Ho3+ is bonded to seven S2- atoms to form distorted HoS7 pentagonal bipyramids that share corners with two equivalent CdS6 octahedra, corners with six HoS6 octahedra, edges with four HoS6 octahedra, edges with two equivalent HoS7 pentagonal bipyramids, and faces with two equivalent HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 21–69°. There are a spread of Ho–S bond distances ranging from 2.70–2.97 Å. In the third Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share a cornercorner with one HoS6 octahedra, a cornercorner with one CdS6 octahedra, corners with four HoS7 pentagonal bipyramids, edges with two equivalent HoS6 octahedra, and edges with six HoS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 54–56°. There are a spread of Ho–S bond distances ranging from 2.65–2.74 Å. In the fourth Ho3+ site, Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share a cornercorner with one HoS6 octahedra, corners with two equivalent CdS6 octahedra, corners with six HoS7 pentagonal bipyramids, edges with two equivalent HoS6 octahedra, edges with three equivalent CdS6 octahedra, and an edgeedge with one HoS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–54°. There are a spread of Ho–S bond distances ranging from 2.64–2.78 Å. Cd2+ is bonded to six S2- atoms to form CdS6 octahedra that share corners with three HoS6 octahedra, corners with six HoS7 pentagonal bipyramids, edges with two equivalent CdS6 octahedra, edges with three equivalent HoS6 octahedra, and an edgeedge with one HoS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–56°. There are a spread of Cd–S bond distances ranging from 2.66–2.79 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded to four Ho3+ and one Cd2+ atom to form distorted SHo4Cd trigonal bipyramids that share corners with five SHo3Cd tetrahedra, corners with four SHo5 trigonal bipyramids, an edgeedge with one SHo4 tetrahedra, and edges with five SHo4Cd trigonal bipyramids. In the second S2- site, S2- is bonded to three Ho3+ and two equivalent Cd2+ atoms to form distorted SHo3Cd2 trigonal bipyramids that share corners with five SHo3Cd tetrahedra, corners with four SHo5 trigonal bipyramids, an edgeedge with one SHo3Cd tetrahedra, and edges with five SHo4Cd trigonal bipyramids. In the third S2- site, S2- is bonded to five Ho3+ atoms to form distorted SHo5 trigonal bipyramids that share corners with four equivalent SHo3Cd tetrahedra, corners with six SHo4Cd trigonal bipyramids, edges with three SHo3Cd tetrahedra, and edges with six SHo3Cd2 trigonal bipyramids. In the fourth S2- site, S2- is bonded to five Ho3+ atoms to form distorted SHo5 trigonal bipyramids that share corners with four equivalent SHo4 tetrahedra, corners with six SHo4Cd trigonal bipyramids, edges with three SHo3Cd tetrahedra, and edges with six SHo4Cd trigonal bipyramids. In the fifth S2- site, S2- is bonded to three Ho3+ and one Cd2+ atom to form distorted SHo3Cd tetrahedra that share corners with three SHo3Cd tetrahedra, corners with nine SHo4Cd trigonal bipyramids, and edges with four SHo3Cd2 trigonal bipyramids. In the sixth S2- site, S2- is bonded to four Ho3+ atoms to form distorted SHo4 tetrahedra that share corners with three SHo3Cd tetrahedra, corners with nine SHo4Cd trigonal bipyramids, and edges with four SHo4Cd trigonal bipyramids. In the seventh S2- site, S2- is bonded in a square co-planar geometry to two equivalent Ho3+ and two equivalent Cd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Enhanced Selectivity for C 2 H 4 Production from C 2 H 6 on Partially Chlorinated IrO 2 (110) Surfaces

Modifying metal oxide surfaces to limit their oxidizing activity can provide a means of improving catalytic selectivity toward the partial oxidation of light alkanes. Here, in this study, we investigated the oxidation of C 2 H 6 on Cl-modified IrO 2 (110) surfaces using temperature-programmed reaction spectroscopy (TPRS) and first-principles microkinetic modeling. We find that substituting Cl for O in the IrO 2 (110) surface enhances the selectivity for C 2 H 6 conversion to C 2 H 4 during TPRS by suppressing extensive oxidation to CO x products, while also either enhancing C 2 H 4 production or altering it to a lesser extent, depending on the initial C 2 H 6 coverage. The C 2 H 4 selectivity increased with increasing C 2 H 6 and Cl coverage, but reached a limiting value below 50%. The Cl coverage changed negligibly during C 2 H 6 oxidation, and the surface reactivity decreased only marginally for Cl coverages up to 0.5 ML (monolayer). TPRS simulations using a microkinetic model predict C 2 H 4 and CO x product yields as a function of the Cl coverage that agree closely with the experimental results. According to the simulations, C 2 H 6 conversion to C 2 H 4 occurs on Cl-IrO 2 (110) by the hydrogenation of C 2 H 3 * species adsorbed in blocked states, in which neighboring sites are occupied only by unreactive HO and Cl species. The microkinetic modeling shows that H-hopping away from surface HO groups provides a relatively efficient route for C 2 H 3 * to escape blocked configurations and dehydrogenate, and that this process can limit the C 2 H 4 selectivity on Cl-IrO 2 (110) under the conditions studied. Overall, our results demonstrate that Cl-substitution into IrO 2 (110) enhances the selectivity for C 2 H 4 production from C 2 H 6 and provides insights into the reaction mechanism that can guide strategies to further improve the C 2 H 4 selectivity.

IrO2↗
DOE OSTI2023

Experimental and Theoretical Studies of the Surface Oxidation Process of Rare–Earth Tritellurides

Recent studies have established Van der Waals (vdW) layered and 2D rare-earth tritellurides (RTe 3 ) as superconductors and near room-temperature charge density wave (CDW) materials. Their environmental stability raises natural concern owing to aging/stability effects observed in other tellurium-based layered crystals. Here, the results establish the stability and environmental aging characteristics of these RTe 3 systems involving a variety of metals such as La, Nd, Sm, Gd, Dy, and Ho. The atomic force microscopy (AFM) and scanning electron microscopy (SEM) results show that all the RTe 3 sheets oxidize to form thin TeO x layers that are primarily confined to the surface, edges, and grain boundaries. Time-resolved in situ Raman spectroscopy measurements are used to understand the kinetics of the oxidization process for different lanthanide metal cations and establish their relative stability/resilience to oxidization. Overall results indicate that the vdW layers show higher air stability as the 4f electron number decreases going from Ho to La, resulting in the most stable LaTe 3 compared to the least stable HoTe 3 . Comprehensive quantum mechanical simulations reveal that environmental degradation originates from a strong oxidizing reaction with O 2 molecules, while humidity (H 2 O) plays a negligible role unless Te vacancies are present. Moreover, the simulations explain the effects of 4f electrons on the work function and Te vacancies formation, which directly impact the aging characteristics of RTe 3 layers. Interestingly, optical and electrical measurements show that the CDW response is still observed in aged RTe 3 layers owing to the presence of underlying pristine/nonoxidized RTe 3 layers, except CDW transition temperatures increase due to the thickness effect. Overall results offer the first in-depth environmental aging studies on these materials, which can be applied to engineer and design their chemical stability, surface properties, and overall CDW characteristics.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho8(AlGe3)3 by Materials Project

Ho8(AlGe3)3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Ho sites. In the first Ho site, Ho is bonded in a 8-coordinate geometry to two equivalent Al and six Ge atoms. Both Ho–Al bond lengths are 3.19 Å. There are a spread of Ho–Ge bond distances ranging from 2.99–3.04 Å. In the second Ho site, Ho is bonded in a 8-coordinate geometry to nine Ge atoms. There are a spread of Ho–Ge bond distances ranging from 3.02–3.60 Å. In the third Ho site, Ho is bonded in a 8-coordinate geometry to two equivalent Al and seven Ge atoms. Both Ho–Al bond lengths are 3.20 Å. There are a spread of Ho–Ge bond distances ranging from 2.98–3.55 Å. In the fourth Ho site, Ho is bonded in a 8-coordinate geometry to two equivalent Al and six Ge atoms. Both Ho–Al bond lengths are 3.19 Å. There are a spread of Ho–Ge bond distances ranging from 3.00–3.04 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 4-coordinate geometry to four Ho and four Ge atoms. There are two shorter (2.65 Å) and two longer (2.67 Å) Al–Ge bond lengths. In the second Al site, Al is bonded in a 4-coordinate geometry to four equivalent Ho and four equivalent Ge atoms. All Al–Ge bond lengths are 2.68 Å. There are five inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to six Ho, two equivalent Al, and one Ge atom. The Ge–Ge bond length is 2.60 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to six Ho and three Ge atoms. There are one shorter (2.56 Å) and two longer (2.73 Å) Ge–Ge bond lengths. In the third Ge site, Ge is bonded in a 9-coordinate geometry to six Ho, two equivalent Al, and one Ge atom. In the fourth Ge site, Ge is bonded in a 9-coordinate geometry to six Ho, two equivalent Al, and one Ge atom. In the fifth Ge site, Ge is bonded to eight Ho and four equivalent Ge atoms to form a mixture of distorted edge and face-sharing GeHo8Ge4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2(B2Rh3)3 by Materials Project

Ho2(Rh3B2)3 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Ho is bonded in a 12-coordinate geometry to one Ho, twelve Rh, and six equivalent B atoms. The Ho–Ho bond length is 3.50 Å. There are six shorter (3.01 Å) and six longer (3.30 Å) Ho–Rh bond lengths. All Ho–B bond lengths are 3.24 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 4-coordinate geometry to two equivalent Ho and four B atoms. There are two shorter (2.14 Å) and two longer (2.16 Å) Rh–B bond lengths. In the second Rh site, Rh is bonded in a distorted square co-planar geometry to four equivalent Ho and four equivalent B atoms. All Rh–B bond lengths are 2.16 Å. There are two inequivalent B sites. In the first B site, B is bonded to six equivalent Rh atoms to form distorted edge-sharing BRh6 pentagonal pyramids. In the second B site, B is bonded in a 6-coordinate geometry to three equivalent Ho and six Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RbHoS2O9 by Materials Project

RbHoS2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Rb is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Rb–O bond distances ranging from 3.01–3.28 Å. Ho is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ho–O bond distances ranging from 2.31–2.44 Å. There are two inequivalent S sites. In the first S site, S is bonded in a tetrahedral geometry to four O atoms. There are a spread of S–O bond distances ranging from 1.48–1.51 Å. In the second S site, S is bonded in a tetrahedral geometry to four O atoms. There are a spread of S–O bond distances ranging from 1.48–1.51 Å. There are nine inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to one Rb, one Ho, and one S atom. In the second O site, O is bonded in a 2-coordinate geometry to one Rb, one Ho, and one S atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one Rb, one Ho, and one S atom. In the fourth O site, O is bonded in a 1-coordinate geometry to one Rb, one Ho, and one S atom. In the fifth O site, O is bonded in a 2-coordinate geometry to one Rb, one Ho, and one S atom. In the sixth O site, O is bonded in a distorted single-bond geometry to one Rb, one Ho, and one S atom. In the seventh O site, O is bonded in a distorted bent 120 degrees geometry to one Rb and one Ho atom. In the eighth O site, O is bonded in a 1-coordinate geometry to one Rb, one Ho, and one S atom. In the ninth O site, O is bonded in a single-bond geometry to one Rb and one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoFe4(CuO4)3 by Materials Project

HoFe4(CuO4)3 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Ho3+ is bonded to twelve equivalent O2- atoms to form HoO12 cuboctahedra that share faces with eight equivalent FeO6 octahedra. All Ho–O bond lengths are 2.60 Å. Fe3+ is bonded to six equivalent O2- atoms to form FeO6 octahedra that share corners with six equivalent FeO6 octahedra and faces with two equivalent HoO12 cuboctahedra. The corner-sharing octahedral tilt angles are 45°. All Fe–O bond lengths are 2.02 Å. Cu3+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.89 Å. O2- is bonded in a 4-coordinate geometry to one Ho3+, two equivalent Fe3+, and one Cu3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Nearly Identical but Not Isotypic: Influence of Lanthanide Contraction on Cs 2 NaLn(PS 4 ) 2 (Ln = La–Nd, Sm, and Gd–Ho)

The effect of the lanthanide contraction often results in topological and symmetry changes in compounds with the same compositions as a function of lanthanide cation size. Here we report on the first example of a lanthanide thiophosphate exhibiting a change in the lanthanide cation environment without any topological or symmetry change. A series of new lanthanide thiophosphates with mixed alkali cations was obtained via a flux crystal growth technique using a CsI flux. The obtained compounds Cs 2 NaLn(PS 4 ) 2 (Ln = La–Nd, Sm, Gd–Ho) were grown as large single crystals (~0.1–1 mm 3 ) and characterized using single crystal X-ray diffraction and magnetic susceptibility measurements. Moving across the series, the structural studies revealed a change in the lanthanide coordination environment dependent upon the identity of the lanthanide. Although all compounds in the Cs 2 NaLn(PS 4 ) 2 series crystallize in the same space group and have the same Wyckoff positions of the atoms, a slight size change between Sm 3+ and Gd 3+ causes a subtle change in coordination number from 9 (for Ln = La–Sm) to 8 (for Ln = Gd–Ho), resulting in two distinct but virtually identical structure types. Ab initio calculations were performed, and the observed experimental trend was corroborated computationally. Finally, magnetic measurements performed on the Cs 2 NaLn(PS 4 ) 2 (Ln = Ce, Pr, Nd, Gd, and Tb) compounds revealed paramagnetic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on HoBiO3 by Materials Project

HoBiO3 is Orthorhombic Perovskite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ho3+ is bonded to six O2- atoms to form corner-sharing HoO6 octahedra. The corner-sharing octahedra tilt angles range from 44–46°. There are two shorter (2.28 Å) and four longer (2.29 Å) Ho–O bond lengths. Bi3+ is bonded in a 3-coordinate geometry to eight O2- atoms. There are a spread of Bi–O bond distances ranging from 2.20–3.01 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two equivalent Bi3+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and three equivalent Bi3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

An experimental and modeling study on auto-ignition kinetics of ammonia/methanol mixtures at intermediate temperature and high pressure

A rapid compression machine (RCM) has been applied to measure the ignition delay times of NH 3 /CH 3 OH mixtures covering pressures of 20 and 40 bar, equivalence ratios of 0.5, 1.0 and 2.0, and temperatures between 845 and 1100 K. Here the measurements show that the NH 3 /CH 3 OH mixtures become more reactive with increasing methanol addition. Addition of merely 1% (molar basis) of CH 3 OH to NH 3 lowers the ignition temperature around 100 K at 40 bar in comparison to pure NH 3 . The ignition delay is a complex function of fuel mixture and stoichiometry. For the 1% CH 3 OH mixture, the leaner mixtures are more reactive, while the reverse trend is found for mixtures with 5%, 20% and pure CH 3 OH. Analysis of the pressure profiles shows three distinct ignition modes for NH 3/ CH 3 OH mixtures, facilitated by the pre-ignition heat release from NH 3 consumption. A detailed mechanism for ignition of NH 3 /CH 3 OH fuel blends has been developed, capable of reproducing the ignition behavior of mixtures with reasonable accuracy. A subset for amine / methanol interactions was established, with rate constants for the key reaction between NH 2 and CH 3 OH calculated from ab initio theory. A sensitivity analysis indicates that the critical reactions during the auto-ignition process vary with the CH 3 OH mole fraction in the fuel. The ammonia chemistry, namely NH 2 + NO, NH2 + NO 2 and NH 2 + HO 2 , is dominant for the mixture with 1% CH 3 OH, while the reactions related to CH 3 OH and H 2 O 2 are more important for the 20% CH 3 OH mixture. The interaction between ammonia and methanol shows a more prominent effect on auto-ignition for mixtures with 5% CH 3 OH in fuel as compared to those with 1% and 20% CH 3 OH. According to the modeling results, methanol addition is found to enrich the O/H radical pool, consuming ammonia and promoting auto-ignition through different reaction pathways.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Ho(Ni2As)2 by Materials Project

Ho(Ni2As)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Ho is bonded to six equivalent As atoms to form a mixture of distorted corner and edge-sharing HoAs6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are two shorter (2.89 Å) and four longer (2.91 Å) Ho–As bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent As atoms. All Ni–As bond lengths are 2.40 Å. As is bonded in a 9-coordinate geometry to three equivalent Ho and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗