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W(CO)6 is Cubic alpha N2-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of twenty-four formaldehyde molecules and four tungsten molecules.
The nonionic deep eutectic solvent, formed by lauric acid (LA) and N-methylacetamide (NMA), has been shown to have a heterogeneous molecular structure in which the LA and NMA form nonpolar and polar domains, respectively. Previous vibrational spectroscopy experiments demonstrated that the ability of the LA domains to solvate compounds was limited to long carbon chains, whereas other nonpolar molecules, such as W(CO) 6 , were found to be solvated by both LA and NMA. These experiments were not fully compatible with the previously proposed micelle-like structure of the nonpolar domains of the LA-NMA DES. In this work, the modeling of the DES molecular structure is pursued using classical molecular dynamics simulations. The new classical model reproduces both the SAXS structural factors and the previously experimentally derived interaction map for these LA-NMA DESs. In addition, the simulation also shows that LA-NMA DESs form highly organized LA aggregates that are difficult to disorganize. Further evidence of the correct description provided by the newly derived model is obtained using a moderately polar probe: chloroform-d. Computations using the classical model have a good agreement with the solvation behavior of the probe derived from experiments, in which the location of the probe is found to be mostly within the polar domain of the DES. The computational model also demonstrates that the probe solvation is a consequence of the tightly packed LA structure, which causes nonpolar molecules to be located at the interphase of the DES nonpolar domains.
In this work, we present a relativistic quantum embedding formalism capable of variationally treating relativistic effects, including scalar-relativity and spin–orbit coupling. We extend density functional theory (DFT)-in-DFT projection-based quantum embedding to a relativistic two-component formalism, where the full spin magnetization vector form is retained throughout the embedding treatment. To benchmark various relativistic embedding schemes, spin–orbit splitting of the nominally t 2g valence manifold of W(CO) 6 , exchange coupling of [(H 3 N) 4 Cr(OH) 2 Cr(NH 3 ) 4 ] 4+ , and the dissociation potential curve of WF 6 are investigated. The relativistic embedding formalism introduced in this work is well suited for efficient modeling of open-shell systems containing late transition metal, lanthanide, and actinide molecular complexes.
Here, this paper presents the phase stability and elemental partitioning in a Co-40Ni-10Al-7.5W-10Cr-3Nb-0.06B-0.6C (at.%) superalloy (referred to as 3Nb) after a two-step heat treatment. The resulting microstructure consisted of γ, γ', MC carbides and µ-Co 7 W 6 phase decorating the regions near and at the grain boundaries. Nb preferentially partitioned to the γ'-phase and other elements such as Ni, Cr and W were responsible for the μ-phase formation.
C7Co6W20 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. there are five inequivalent W sites. In the first W site, W is bonded in a 3-coordinate geometry to three Co and three C atoms. There are two shorter (2.79 Å) and one longer (2.84 Å) W–Co bond lengths. There are two shorter (2.17 Å) and one longer (2.26 Å) W–C bond lengths. In the second W site, W is bonded in a 2-coordinate geometry to three Co and two equivalent C atoms. There are two shorter (2.75 Å) and one longer (2.80 Å) W–Co bond lengths. Both W–C bond lengths are 2.14 Å. In the third W site, W is bonded in a distorted rectangular see-saw-like geometry to two equivalent Co and two equivalent C atoms. Both W–Co bond lengths are 2.62 Å. Both W–C bond lengths are 2.08 Å. In the fourth W site, W is bonded in a distorted rectangular see-saw-like geometry to two equivalent Co and two equivalent C atoms. Both W–Co bond lengths are 2.63 Å. Both W–C bond lengths are 2.09 Å. In the fifth W site, W is bonded in a 6-coordinate geometry to six Co atoms. There are three shorter (2.48 Å) and three longer (2.49 Å) W–Co bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded to ten W and two equivalent Co atoms to form distorted CoCo2W10 cuboctahedra that share corners with two equivalent CoCo2W10 cuboctahedra, corners with four equivalent CW6 octahedra, faces with two equivalent CoCo2W10 cuboctahedra, and faces with four equivalent CW6 octahedra. The corner-sharing octahedral tilt angles are 39°. Both Co–Co bond lengths are 2.63 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to ten W and two equivalent Co atoms. Both Co–Co bond lengths are 2.62 Å. There are two inequivalent C sites. In the first C site, C is bonded in a 6-coordinate geometry to six equivalent W atoms. In the second C site, C is bonded to six W atoms to form CW6 octahedra that share corners with two equivalent CoCo2W10 cuboctahedra, corners with six equivalent CW6 octahedra, and faces with two equivalent CoCo2W10 cuboctahedra. The corner-sharing octahedra tilt angles range from 38–50°.
Mixed metal oxides (MMOs) are a promising class of electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Despite their importance for sustainable energy schemes, our understanding of relevant reaction pathways, catalytically active sites, and synergistic effects is rather limited. Here, we applied synchrotron-based X-ray absorption spectroscopy (XAS) to explore the evolution of the amorphous Co–Cu–W MMO electrocatalyst, shown previously to be an efficient bifunctional OER and HER catalyst for water splitting. Ex situ XAS measurements provided structural environments and the oxidation state of the metals involved, revealing Co 2+ (octahedral), Cu + / 2+ (tetrahedral/square-planar), and W 6+ (octahedral) centers. Operando XAS investigations, including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), elucidated the dynamic structural transformations of Co, Cu, and W metal centers during the OER and HER. The experimental results indicate that Co 3+ and Cu 0 are the active catalytic sites involved in the OER and HER, respectively, while Cu 2+ and W 6+ play crucial roles as structure stabilizers, suggesting strong synergistic interactions within the Co–Cu–W MMO system. In conclusion, these results, combined with the Tafel slope analysis, revealed that the bottleneck intermediate during the OER is Co 3+ hydroperoxide, whose formation is accompanied by changes in the Cu–O bond lengths, pointing to a possible synergistic effect between Co and Cu ions. Our study reveals important structural effects taking place during MMO-driven OER/HER electrocatalysis and provides essential experimental insights into the complex catalytic mechanism of emerging noble-metal-free MMO electrocatalysts for full water splitting.
We report the synthesis, characterization, and solution self-assembly of plenary Nb 6 P 2 W 12 -based transition-metal substituted polyoxometalate, which is obtained by simply adding transition metals (Co 2+ ) into aqueous solution containing cluster [(NbO 2 ) 6 P 2 W 12 O 56 ] 12- , which is obtained by an in situ synthetic method. The incorporation of Co 2+ ions significantly affects the crystal structure, resulting in the formation of a 1D chain-like crystal and the first example of a niobotungstate-based cobalt derivative cluster. The behavior and stability of this cluster in solution are confirmed by time-resolved static light scattering, dynamic light scattering, small-angle X-ray scattering, and electrospray mass spectrometry studies.
W3Te2(CO)6(CO)9 is Magnesium tetraboride-like structured and crystallizes in the tetragonal P4_12_12 space group. The structure is zero-dimensional and consists of thirty-six formaldehyde molecules and four W3Te2(CO)6 clusters. In each W3Te2(CO)6 cluster, there are two inequivalent W+4.67+ sites. In the first W+4.67+ site, W+4.67+ is bonded in a distorted single-bond geometry to one Te2- atom. The W–Te bond length is 2.83 Å. In the second W+4.67+ site, W+4.67+ is bonded in a 2-coordinate geometry to two equivalent Te2- atoms. Both W–Te bond lengths are 3.00 Å. There are three inequivalent C+1.33+ sites. In the first C+1.33+ site, C+1.33+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.16 Å. In the second C+1.33+ site, C+1.33+ is bonded in a single-bond geometry to one Te2- and one O2- atom. The C–Te bond length is 3.06 Å. The C–O bond length is 1.16 Å. In the third C+1.33+ site, C+1.33+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.17 Å. Te2- is bonded in a 2-coordinate geometry to two W+4.67+, one C+1.33+, one Te2-, and two O2- atoms. The Te–Te bond length is 2.78 Å. There are one shorter (3.42 Å) and one longer (3.81 Å) Te–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ and one Te2- atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ and one Te2- atom.
We report an order and disorder combined corrosion morphology of dual-phase Ni-based alloy in the passive state. After galvanostatic polarization in the passive region, the surface of the γ(Ni) phase presents amorphous feature while that of the γ′(Ni 3 Al) phase maintains crystalline. The variations in weight percentages of Ni (50.19% → 3.80%), Co (19.24% → 0.65%), Ta (0.85% → 21.19%), and W (5.73% → 43.79%) of γ surface are evident, whereas the composition of γ′ surface is nearly unchanged. The passive film comprises $W^{6+}_{ox}$, $Ta^{5+}_{ox}$, $Cr^{3+}_{ox}$, $Co^{8/3+}_{ox}$, $Ni^{2+}_{hy}$, and $Co^{2+}_{hy}$, and it shows stronger protection effect on the γ phase.
Hf9W4Co crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded in a 1-coordinate geometry to four W and one Co atom. There are a spread of Hf–W bond distances ranging from 2.94–3.09 Å. The Hf–Co bond length is 2.56 Å. In the second Hf site, Hf is bonded in a 2-coordinate geometry to two equivalent W atoms. Both Hf–W bond lengths are 2.89 Å. There are two inequivalent W sites. In the first W site, W is bonded in a 12-coordinate geometry to eight Hf and four W atoms. There are two shorter (2.71 Å) and two longer (2.93 Å) W–W bond lengths. In the second W site, W is bonded to six equivalent Hf and six equivalent W atoms to form face-sharing WHf6W6 cuboctahedra. Co is bonded in a 6-coordinate geometry to six equivalent Hf atoms.
Anomalous lattice expansion of bcc Ta is observed in helium-loaded diamond anvil cell (DAC) experiments near 6 GPa and above 400 K, while co-loaded W, Mo, and Au exhibit normal thermal expansion. The Ta volume expansion increases with temperature, reaching ~14% near 650 K before plateauing, and is largely retained after recovery to ambient conditions. Time-resolved measurements at 500 K reveal progressive expansion over several hours, consistent with gradual, thermally activated He incorporation. The largely retained expansion during subsequent cooling and holding at 400 K indicates that the incorporated He is predominantly kinetically trapped. The data reveal two distinct regimes: below ~550 K, modest and spatially uniform expansion consistent with interstitial He trapping at isolated, randomly distributed vacancies; above ~550 K, He-vacancy cluster growth producing dramatically larger expansion, peak broadening, and a core–shell microstructure revealed by micron-resolution X-ray diffraction mapping. These results demonstrate that He is not always a passive pressure medium in DAC experiments and reveal a previously unrecognized regime of He-mediated lattice modification in Ta, complementing conventional ion-implantation studies relevant to nuclear and fusion structural materials.
Selective reduction of CO 2 into fuels and chemical feedstocks is highly desirable to reduce our dependence on fossil fuels. Most molecular catalysts afford 2e – reduction products, such as CO or HCO 2 – , as opposed to more reduced products. Here we present an analysis of the thermodynamic limitations for reduction of the CO ligand in the form of a series of isostructural group 6 carbonyl complexes, Cp*M(CO) 3 (P(OMe) 3 ) + (M = Cr, Mo, and W). Additionally, the free energy for stepwise transfer of a hydride (H – ) and a proton (H + ) to the CO ligand, resulting in a hydroxycarbene (CHOH) complex, was measured by equilibration with H – /H + donors and acceptors with known hydricity or acidity. Together, these two reaction steps are equivalent to a net addition of H 2 across the CO ligand. A large and unfavorable free energy for H 2 addition (Δ G ° H2 ) was measured for all three complexes and decreases in the order Cr > Mo > W. The trend for these complexes is opposite to the trend previously reported for group 7 carbonyl complexes, for which Δ G ° H2 decreases moving up the group, Re > Mn. Computational analysis indicates the trends can be described in terms of electrostatic effects, where a low Δ G ° H2 is obtained in complexes that balance the atomic charges of the M–C≡O fragment of the complex. These findings can be used to design metal carbonyl complexes with a more energetically accessible H 2 addition, which will facilitate the development of molecular catalysts for reduction of CO.
W2CoB2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. W2+ is bonded in a 6-coordinate geometry to six equivalent B3- atoms. There are four shorter (2.34 Å) and two longer (2.52 Å) W–B bond lengths. Co2+ is bonded in a square co-planar geometry to four equivalent B3- atoms. All Co–B bond lengths are 2.09 Å. B3- is bonded in a 9-coordinate geometry to six equivalent W2+, two equivalent Co2+, and one B3- atom. The B–B bond length is 1.88 Å.
Solid sorbents made of small amine molecules and polyamines infused into mesoporous substrates are promising materials for CO 2 capture technologies. To date, their preparation is mainly based on wet infusion with focus on increasing amine content by varying the structure of the amine sorbent and designing solid substrates of various pore parameters. Less explored in the field are changes in processing to afford efficient CO 2 sorbents. In this study, branched poly(ethylenimine) (bPEI, M w = 800 Da) alone and blends with linear poly(propylenimine) (LPPI, M n = 6,700 Da) are infused into solid SBA-15 substrates by a method that varies the solution processing called sequential polymer infusion into solid substrates (SPISS). The reference 40 % bPEI-SBA-15 samples are split by two methods: split batch in dry suspension (SBD) and split batch in liquid suspension (SBL). Sequentially, alcoholic 10% of bPEI (non-blends) and 10% of LPPI (blends) solutions are introduced to afford the desired products. Under dry conditions, the resulting 50% bPEI-SBA-15 SBD & SBL sorbents display high CO 2 capacities up to 3.47 mmol CO 2 /g SiO 2 for simulated flue gas (10% CO 2 ) and 2.62 mmol CO 2 /g SiO 2 for direct air capture (DAC, 400 ppm CO 2 ). Under humid DAC conditions the CO 2 performance is further enhanced with an uptake of 4.62 mmol CO 2 /gSiO 2 and amine efficiency of 0.22 mmol CO 2 /mmol N. Subjected to extended temperature swing adsorption kinetic cycling (20 cycles), the SPISS samples display stable working capacities and retain over 70% (blends) and over 90% (non-blends) of their initial 12 h adsorption performance. LPPI is demonstrated to be an effective water sorption limiting agent using dynamic vapor sorption measurements. Solid state NMR techniques reveal important insights into the dynamics of the amine polymers confined into SBA-15 pores, as impacted by processing conditions. The results suggest that the conformation of the polymers is different depending on the processing method, displaying relatively tight (SBD) and loose (SBL) packing. Finally, the simple solution processing approaches presented here show that processing variations may guide the design of solid amine sorbents with desirable properties relevant for integration into CO 2 capture technologies.
W3CoB3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent W+2.33+ sites. In the first W+2.33+ site, W+2.33+ is bonded in a 7-coordinate geometry to seven B3- atoms. There are a spread of W–B bond distances ranging from 2.36–2.49 Å. In the second W+2.33+ site, W+2.33+ is bonded in a 6-coordinate geometry to six B3- atoms. There are a spread of W–B bond distances ranging from 2.32–2.52 Å. Co2+ is bonded in a square co-planar geometry to four equivalent B3- atoms. All Co–B bond lengths are 2.07 Å. There are two inequivalent B3- sites. In the first B3- site, B3- is bonded in a 9-coordinate geometry to seven W+2.33+ and two equivalent B3- atoms. Both B–B bond lengths are 1.90 Å. In the second B3- site, B3- is bonded in a 9-coordinate geometry to six W+2.33+, two equivalent Co2+, and one B3- atom.
The present work focuses on predicting temperature-dependent mechanical properties of Ni-based concentrated alloys Ni 18 Cr 10 Co 10 Fe 6 M 4 (abbreviated by X 44 M 4 , with M = Al, V, Mn, Fe, Nb, Mo, and W) using density functional theory (DFT). These predictions are based on shear (plastic) and elastic deformations, utilizing the special quasirandom structure (SQS), the phonon-based quasiharmonic approach (QHA), and the quasistatic approach. The resulting properties include coefficient of thermal expansion via QHA, ideal shear strength (τ IS ), and stable and unstable stacking fault energies (γ SF and γ US ) through pure alias shear deformation, and elastic constants (c ij ), bulk modulus (B 0 ), and shear modules (G 0 ) via elastic deformation. Notably, predicting accurate γ SF is challenging due to uncertainties that can exceed the γ SF values. τ IS and γ US exhibit a strong linear relationship, enabling the accurate prediction of γ US based on the precisely determined τ IS . All mechanical properties of X 44 M 4 decrease with increasing temperature, except for some γ SF cases such as X 44 M 4 with M = V, Mn, Fe, Mo, and W. Among the X 44 M 4 alloys, X 44 Nb 4 exhibits the lowest τ IS , γ US , and G 0 values, and the highest B 0 /G 0 ratio, while X 44 Mn 4 has the lowest B 0 and B 0 /G 0 ratio. We found that volume is a crucial descriptor for understanding and modeling mechanical properties (except B0 and maybe also γ SF ) affected by alloying elements and temperature. Ni-based dilute alloys (e.g., Ni 11 M 1 and Ni 31 M 1 ) and concentrated alloys (e.g., X 44 M 4 ) show similar trends in mechanical properties influenced by alloying elements and temperature, simplifying the analysis and design of Ni-based alloys.
W5ZnO7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent W+2.40+ sites. In the first W+2.40+ site, W+2.40+ is bonded to six O2- atoms to form edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 2.12–2.45 Å. In the second W+2.40+ site, W+2.40+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of W–O bond distances ranging from 2.11–2.67 Å. In the third W+2.40+ site, W+2.40+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All W–O bond lengths are 2.53 Å. Zn2+ is bonded in a see-saw-like geometry to four O2- atoms. There are two shorter (2.04 Å) and two longer (2.18 Å) Zn–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four W+2.40+ and one Zn2+ atom to form distorted OZnW4 trigonal bipyramids that share a cornercorner with one OZnW4 trigonal bipyramid, edges with two equivalent OZn2W2 tetrahedra, and edges with two equivalent OZnW4 trigonal bipyramids. In the second O2- site, O2- is bonded to two equivalent W+2.40+ and two equivalent Zn2+ atoms to form OZn2W2 tetrahedra that share corners with two equivalent OZn2W2 tetrahedra and edges with four equivalent OZnW4 trigonal bipyramids. In the third O2- site, O2- is bonded in a 6-coordinate geometry to six W+2.40+ atoms. In the fourth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three W+2.40+ atoms.
Solid oxide electrochemical cells (SOECs) stand out as a highly promising clean energy technology that offers several benefits, showing significant potential to play a pivotal role in the transition towards a sustainable and low-carbon energy future. SOECs can efficiently convert the chemical energy stored in fuels to electricity in fuel cell mode, and produce various chemicals from abundant feedstocks (e.g., CO 2 , H 2 O) and intermittent solar/wind-based renewable electricity. Despite extensive efforts that have been devoted to designing novel materials and optimizing SOEC manufacturing processes, aiming to achieve enhanced energy efficiency, the current SOECs still suffer from poor performance, which is mainly due to the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics. To address this challenge, in this work, we have successfully designed an in situ formed hybrid oxygen electrode material (Pr 1.39 Ba 0.14 Sr 0.53 Co 1.48 Fe 0.76 O 6- δ -Ba 0.66 Sr 0.34 CoO 3- δ ), which significantly improves the surface oxygen exchange coefficient and bulk oxygen-ion diffusion coefficient, enhancing the OER and ORR electrocatalytic activities. Further, the SOECs equipped with this newly developed oxygen electrode achieved exceptional performance for power generation using both hydrogen and propane as the fuels. At 750 °C, a peak power density of 2.4 W cm -2 was obtained with H 2 as the fuel. Additionally, the SOECs attain unprecedented performance in steam electrolysis mode. A current density of 4.4 A cm -2 was achieved at 1.3 V and 750 °C, which represents the highest performance among all yttria-stabilized zirconia (YSZ) electrolyte-based SOECs. The SOECs also deliver remarkable stability during the accelerated stability testing, highlighting the great potential of Pr 1.39 Ba 0.14 Sr 0.53 Co 1.48 Fe 0.76 O 6- δ -Ba 0.66 Sr 0.34 CoO 3- δ as a high-performance oxygen electrode for next generation SOECs.