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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Hf9W4S by Materials Project

Hf9W4S 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 S atom. There are a spread of Hf–W bond distances ranging from 2.89–3.09 Å. The Hf–S bond length is 2.68 Å. In the second Hf site, Hf is bonded in a distorted T-shaped geometry to two equivalent W and one S atom. Both Hf–W bond lengths are 2.91 Å. The Hf–S bond length is 3.14 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 (2.72 Å) and two longer (2.89 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. S is bonded in a 6-coordinate geometry to nine Hf atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf9CoW4 by Materials Project

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.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al3Co(W3C)3 by Materials Project

W9Al3CoC3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent W sites. In the first W site, W is bonded in a 2-coordinate geometry to one Co, three equivalent Al, and two equivalent C atoms. The W–Co bond length is 2.85 Å. There are two shorter (2.80 Å) and one longer (2.83 Å) W–Al bond lengths. Both W–C bond lengths are 2.16 Å. In the second W site, W is bonded in a distorted rectangular see-saw-like geometry to two equivalent Al and two equivalent C atoms. Both W–Al bond lengths are 2.66 Å. Both W–C bond lengths are 2.09 Å. Co is bonded to six equivalent W and six equivalent Al atoms to form CoAl6W6 cuboctahedra that share edges with six equivalent CW6 octahedra, faces with two equivalent CoAl6W6 cuboctahedra, and faces with six equivalent AlAl2Co2W8 cuboctahedra. All Co–Al bond lengths are 2.48 Å. Al is bonded to eight W, two equivalent Co, and two equivalent Al atoms to form distorted AlAl2Co2W8 cuboctahedra that share corners with four equivalent AlAl2Co2W8 cuboctahedra, corners with four equivalent CW6 octahedra, faces with two equivalent CoAl6W6 cuboctahedra, faces with six equivalent AlAl2Co2W8 cuboctahedra, and faces with four equivalent CW6 octahedra. The corner-sharing octahedral tilt angles are 39°. Both Al–Al bond lengths are 2.63 Å. C is bonded to six W atoms to form CW6 octahedra that share corners with four equivalent AlAl2Co2W8 cuboctahedra, corners with six equivalent CW6 octahedra, edges with two equivalent CoAl6W6 cuboctahedra, and faces with four equivalent AlAl2Co2W8 cuboctahedra. The corner-sharing octahedra tilt angles range from 40–46°.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High‐Pressure Synthesis of Ultra‐Incompressible, Hard and Superconducting Tungsten Nitrides

Abstract Transition metal nitrides, particularly those of 5 d metals, are known for their outstanding properties, often relevant for industrial applications. Among these metal elements, tungsten is especially attractive given its low cost. In this high‐pressure investigation of the W–N system, two novel ultra‐incompressible tungsten nitride superconductors, namely W 2 N 3 and W 3 N 5 , are successfully synthesized at 35 and 56 GPa, respectively, through a direct reaction between N 2 and W in laser‐heated diamond anvil cells. Their crystal structure is determined using synchrotron single‐crystal X‐ray diffraction. While the W 2 N 3 solid's sole constituting nitrogen species are N 3‐ units, W 3 N 5 features both discrete N 3‐ as well as N 2 4‐ pernitride anions. The bulk modulus of W 2 N 3 and W 3 N 5 is experimentally determined to be 380(3) and 406(7) GPa, and their ultra‐incompressible behavior is rationalized by their constituting WN 7 polyhedra and their linkages. Importantly, both W 2 N 3 and W 3 N 5 are recoverable to ambient conditions and stable in air. Density functional theory calculations reveal W 2 N 3 and W 3 N 5 to have a Vickers hardness of 30 and 34 GPa, and superconducting transition temperatures at ambient pressure (50 GPa) of 11.6 K (9.8 K) and 9.4 K (7.2 K), respectively. Additionally, transport measurements performed at 50 GPa on W 2 N 3 corroborate with the calculations.

Chemistry↗
DOE OSTI2021

In situ synchrotron X-ray imaging and mechanical properties characterization of additively manufactured high-entropy alloy composites

Laser beam directed energy deposition has become an increasingly popular advanced manufacturing technique for materials discovery as a result of the in situ alloying capability. In this study, we leverage an additive manufacturing enabled high throughput materials discovery approach to explore the composition space of a graded W x (CoCrFeMnNi) 100–x sample spanning 0 ≤ x ≤ 21 at%. In addition to microstructural and mechanical characterization, synchrotron high speed x-ray computer aided tomography was conducted on a W 20 (CoCrFeMnNi) 80 composition to visualize melting dynamics, powder-laser interactions, and remelting effects of previously consolidated material. Results reveal the formation of the Fe 7 W 6 intermetallic phase at W concentrations> 6 at%, despite the high configurational entropy. Unincorporated W particles also occurred at W concentrations> 10 at% accompanied by a dissolution band of Fe 7 W 6 at the W/matrix interface and hardness values greater than 400 HV. In this work, the primary strengthening mechanism is attributed to the reinforcement of the Fe 7 W 6 and W phases as a metal matrix composite. The in situ high speed x-ray imaging during remelting showed that an additional laser pass did not promote further mixing of the Fe 7 W 6 or W phases suggesting that, despite the dissolution of the W into the Fe 7 W 6 phase being thermodynamically favored, it is kinetically limited by the thickness/diffusivity of the intermetallic phase, and the rapid solidification of the laser-based process.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Molybdenum and Tungsten isotope compositions of UO 2 fuel pellets: Implications for isotopically enriched taggants

The addition of isotopically enriched taggants to material at the front end of the nuclear fuel cycle could be a powerful tool used to assist law enforcement authorities should material outside of regulatory control be found. Two potential candidates for this purpose are molybdenum (Mo) and tungsten (W) as both elements have five or more stable isotopes and are trace elements contained within nuclear fuel. So there is a concern that Mo and W could undergo isotope fractionation during processes like uranium enrichment and to date, it is unknown if nuclear fuels have natural Mo and W isotope compositions. If Mo and W isotopic variability is present in nuclear fuels, this would hinder the use of these elements as isotopic taggants because it would be difficult to discern the original taggant isotope composition with high confidence. Therefore, a set of 16 low enriched uranium (LEU) fuel pellets from US commercial producers was analyzed using multi collector-inductively coupled plasma mass spectrometry (MC-ICPMS) to determine Mo and W isotope compositions (i.e., 94 Mo/ 92 Mo, 95 Mo/ 92 Mo, 96 Mo/ 92 Mo, 97 Mo/ 92 Mo, 98 Mo/ 92 Mo, 183 W/ 182 W, 184 W/ 182 W, and 186 W/ 182 W). Relative to terrestrial standards, LEU fuel pellets have variable Mo and W isotope compositions, thereby complicating the use of these elements as isotopically enriched taggants. As such, this work demonstrates that the isotope composition of any potential taggant must be well characterized in the base nuclear fuel prior to any taggant addition. Furthermore, these results suggest that Mo and W are not ideal candidates for isotopically enriched taggants.

58 GEOSCIENCES↗
DOE OSTI2024

Assessing observational constraints on dark energy

Observational constraints on time-varying dark energy (e.g., quintessence) are commonly presented on a w 0 –w a plot that assumes the equation of state of dark energy strictly satisfies w(z) = w 0 + w a z/(1 + z) as a function of the redshift z. Recent observations favor a sector of the w 0 –w a plane in which w 0 > –1 and w 0 + w a < –1, suggesting that the equation of state underwent a transition from violating the null energy condition (NEC) at large z to obeying it at small z. In this paper, we demonstrate that this impression is misleading by showing that simple quintessence models satisfying the NEC for all z predict an observational preference for the same sector. We also find that quintessence models that best fit observational data can predict a value for the dark energy equation of state at present that is significantly different from the best-fit value of w 0 obtained assuming the parameterization above. In addition, the analysis reveals an approximate degeneracy of the w 0 –w a parameterization that explains the eccentricity and orientation of the likelihood contours presented in recent observational studies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

A classical model for three-body interactions in aqueous ionic systems

We present a classical induction model to evaluate the three-body ion–water–water (I–W–W) and water–water–water (W–W–W) interactions in aqueous ionic systems. The classical description of the induction energy is based on electrostatic distributed multipoles up to hexadecapole and distributed polarizabilities up to quadrupole–quadrupole on the O and H atoms of water. The monatomic ions were described by a point charge and a dipole–dipole polarizability, while for the polyatomic ions, distributed multipoles up to hexadecapole and distributed polarizabilities up to quadrupole–quadrupole were used. The accuracy of the classical model is benchmarked against an accurate dataset of 936 (I–W–W) and 2184 (W–W–W) three-body terms for 13 different monatomic and polyatomic cation and anion systems. The classical model shows excellent agreement with the reference second order Moller–Plesset and coupled-cluster single double and perturbative triple [CCSD(T)] three-body energies. The Root-Mean-Square-Errors (RMSEs) for monatomic cations, monatomic anions, and polyatomic ions were 0.29, 0.25, and 0.12 kcal/mol, respectively. The corresponding RMSE for 1744 CCSD(T)/aVTZ three-body (W–W–W) energies, used to train MB-pol, was 0.12 kcal/mol. The accuracy of the proposed classical model demonstrates that the three-body term for aqueous ionic systems can be accurately modeled classically. This approach provides a fast, efficient, and as-accurate path toward modeling the three-body term in aqueous ionic systems that is fully transferable across systems with different ions without the need to fit to tens of thousands of ab initio calculations for each ion to extend existing many-body force fields to interactions between water and ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

First use of an InSb crystal for x-ray imaging spectroscopy of highly ionized tungsten in the Wendelstein 7-X stellarator

Advances in time and space resolved measurements of highly charged states of tungsten (W) through x-ray imaging spectroscopy have enabled investigation of impurity transport in the Wendelstein 7-X (W7-X) stellarator. The high-resolution x-ray imaging spectrometer (HR-XIS) system on W7-X utilizes the Bragg diffraction properties of a set of multiple crystals to measure a range of impurity emission lines within sections of the 1–7 Å wavelength range, including transitions of W. A new indium–antimonide crystal has been installed on the HR-XIS system to allow viewing of the 5.5–6.2 Å region focusing on emissions of W. Consequently, many bright W emission lines from W 40+ to W 47+ were observed in this wavelength range, both in plasmas with injected W and in those with only intrinsic W impurity sources, showing the high sensitivity of the diagnostic. Three W 46+ emissions correspond in wavelength and intensity with calculated photon emissivity coefficients and can be exploited for W transport and concentration applications in plasmas with T e ≳ 2.1 keV. Here, an estimate of the core W density behavior in two separate turbulence-reduced ‘high-performance’ (HP) discharges on W7-X is done using the 5.6893 Å W 46+ line. The n W behavior in HP scenarios can be explained by previous experimental results and neoclassical predictions.

XICS↗
DOE OSTI2020

Materials Data on W3Br8 by Materials Project

W3Br8 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are two inequivalent W+2.67+ sites. In the first W+2.67+ site, W+2.67+ is bonded to five Br1- atoms to form edge-sharing WBr5 square pyramids. There are a spread of W–Br bond distances ranging from 2.59–2.61 Å. In the second W+2.67+ site, W+2.67+ is bonded to five Br1- atoms to form edge-sharing WBr5 square pyramids. There are a spread of W–Br bond distances ranging from 2.54–2.68 Å. There are six inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a single-bond geometry to one W+2.67+ atom. In the second Br1- site, Br1- is bonded in a 8-coordinate geometry to three W+2.67+ and one Br1- atom. The Br–Br bond length is 3.86 Å. In the third Br1- site, Br1- is bonded in a 4-coordinate geometry to three W+2.67+ and one Br1- atom. The Br–Br bond length is 3.82 Å. In the fourth Br1- site, Br1- is bonded in a 1-coordinate geometry to three W+2.67+ and one Br1- atom. The Br–Br bond length is 3.98 Å. In the fifth Br1- site, Br1- is bonded in a 2-coordinate geometry to six Br1- atoms. There are one shorter (2.42 Å) and one longer (3.10 Å) Br–Br bond lengths. In the sixth Br1- site, Br1- is bonded in a single-bond geometry to one W+2.67+ and one Br1- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on W3C by Materials Project

CW3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent W sites. In the first W site, W is bonded to eight W and four equivalent C atoms to form distorted WW8C4 cuboctahedra that share corners with twelve equivalent WW8C4 cuboctahedra, edges with eight equivalent WW8C4 cuboctahedra, edges with eight equivalent CW12 cuboctahedra, faces with four equivalent CW12 cuboctahedra, and faces with ten equivalent WW8C4 cuboctahedra. There are four shorter (2.50 Å) and four longer (2.87 Å) W–W bond lengths. All W–C bond lengths are 2.87 Å. In the second W site, W is bonded in a square co-planar geometry to eight equivalent W and four equivalent C atoms. All W–C bond lengths are 2.50 Å. C is bonded to twelve W atoms to form distorted CW12 cuboctahedra that share corners with four equivalent CW12 cuboctahedra, edges with eight equivalent CW12 cuboctahedra, edges with sixteen equivalent WW8C4 cuboctahedra, faces with four equivalent CW12 cuboctahedra, and faces with eight equivalent WW8C4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(WO2)2 by Materials Project

Ca(WO2)2 is Spinel-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three equivalent CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–70°. There are a spread of Ca–O bond distances ranging from 2.27–2.33 Å. In the second Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three equivalent CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 53–68°. There are a spread of Ca–O bond distances ranging from 2.23–2.34 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three equivalent CaO4 tetrahedra and edges with six WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.27–2.40 Å. In the fourth Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with twelve WO6 octahedra. The corner-sharing octahedra tilt angles range from 53–65°. There are a spread of Ca–O bond distances ranging from 2.25–2.39 Å. In the fifth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three equivalent CaO4 tetrahedra, corners with three equivalent WO4 trigonal pyramids, and edges with six WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.41 Å. In the sixth Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with twelve WO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Ca–O bond distances ranging from 2.26–2.33 Å. There are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three CaO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.30 Å. In the second W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three CaO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.27 Å. In the third W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with five CaO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.29 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three CaO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.02–2.21 Å. In the fifth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with five CaO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.25 Å. In the sixth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six CaO4 tetrahedra and edges with six WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.24 Å. In the seventh W3+ site, W3+ is bonded in a distorted trigonal planar geometry to three O2- atoms. There are a spread of W–O bond distances ranging from 2.04–2.29 Å. In the eighth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with four CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.23 Å. In the ninth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with five CaO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.05–2.19 Å. In the tenth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with four CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.26 Å. In the eleventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with four CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.22 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form distorted WO4 trigonal pyramids that share corners with three equivalent CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 42–75°. There are a spread of W–O bond distances ranging from 2.03–2.60 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 trigonal pyramids that share a cornercorner with one OCaW3 tetrahedra, corners with four OCa2W2 trigonal pyramids, an edgeedge with one OCaW3 tetrahedra, and edges with two OCa2W2 trigonal pyramids. In the second O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form a mixture of distorted edge and corner-sharing OCaW3 tetrahedra. In the third O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 trigonal pyramids that share a cornercorner with one OCaW3 tetrahedra, corners with four OCa2W2 trigonal pyramids, an edgeedge with one OCaW3 tetrahedra, and edges with two OCa2W2 trigonal pyramids. In the fourth O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 trigonal pyramids that share a cornercorner with one OCaW3 tetrahedra, corners with four OCa2W2 trigonal pyramids, an edgeedge with one OCaW3 tetrahedra, and edges with two OCa2W2 trigonal pyramids. In the fifth O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 trigonal pyramids that share corners with five OCaW3 tetrahedra, corners with four OW4 trigonal pyramids, an edgeedge with one OCaW3 tetrahedra, and edges with two OCa2W2 trigonal pyramids. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the seventh O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 tetrahedra that share corners with nine OCaW3 tetrahedra, corners with three equivalent OW4 trigonal pyramids, and edges with three OCa2W2 trigonal pyramids. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two W3+ atoms. In the ninth O2- site, O2- is bonded to four W3+ atoms to form distorted OW4 trigonal pyramids that share corners with three equivalent OCaW3 tetrahedra and corners with six OCa2W2 trigonal pyramids. In the tenth O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 trigonal pyramids that share corners with five OCaW3 tetrahedra, corners with four OW4 trigonal pyramids, an edgeedge with one OCaW3 tetrahedra, and edges with two OCa2W2 trigonal pyramids. In the eleventh O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 trigonal pyramids that share corners with five OCaW3 tetrahedra, corners with four OW4 trigonal pyramids, an edgeedge with one OCaW3 tetrahedra, and edges with two OCa2W2 trigonal pyramids. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the thirteenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form a mixture of distorted edge and corner-sharing OCaW3 tetrahedra. In the fourteenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 tetrahedra that share corners with eight OCaW3 tetrahedra, corners with four OCa2W2 trigonal pyramids, edges with two OCaW3 tetrahedra, and an edgeedge with one OW4 trigonal pyramid. In the fifteenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 tetrahedra that share corners with eight OCaW3 tetrahedra, corners with four OCa2W2 trigonal pyramids, edges with two OCaW3 tetrahedra, and an edgeedge with one OW4 trigonal pyramid. In the sixteenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 tetrahedra that share corners with three equivalent OCaW3 tetrahedra, corners with three OCa2W2 trigonal pyramids, and edges with three OCaW3 tetrahedra. In the seventeenth O2- site, O2- is bonded to four W3+ atoms to form distorted OW4 trigonal pyramids that share corners with three equivalent OCaW3 tetrahedra, corners with six OCa2W2 trigonal pyramids, and edges with three OCaW3 tetrahedra. In the eighteenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form a mixture of distorted edge and corner-sharing OCaW3 tetrahedra. In the nineteenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form a mixture of distorted edge and corner-sharing OCaW3 tetrahedra. In the twentieth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 tetrahedra that share corners with eight OCaW3 tetrahedra, corners with four OCa2W2 trigonal pyramids, edges with two OCaW3 tetrahedra, and an edgeedge with one OW4 trigonal pyramid. In the twenty-first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twenty-second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twenty-third O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted corner-sharing OCaW3 tetrahedra. In the twenty-fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on WO2 by Materials Project

WO2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twelve inequivalent W4+ sites. In the first W4+ site, W4+ is bonded to six O2- atoms to form distorted WO6 octahedra that share a cornercorner with one WO4 tetrahedra and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.00–2.32 Å. In the second W4+ site, W4+ is bonded to six O2- atoms to form distorted edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 2.18–2.25 Å. In the third W4+ site, W4+ is bonded to six O2- atoms to form edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 2.06–2.19 Å. In the fourth W4+ site, W4+ is bonded to six O2- atoms to form distorted WO6 octahedra that share a cornercorner with one WO4 tetrahedra and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 1.90–2.29 Å. In the fifth W4+ site, W4+ is bonded to six O2- atoms to form edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 2.07–2.18 Å. In the sixth W4+ site, W4+ is bonded to six O2- atoms to form distorted WO6 octahedra that share a cornercorner with one WO4 tetrahedra and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 1.98–2.31 Å. In the seventh W4+ site, W4+ is bonded to six O2- atoms to form edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 1.95–2.11 Å. In the eighth W4+ site, W4+ is bonded to six O2- atoms to form edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 2.02–2.21 Å. In the ninth W4+ site, W4+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent WO4 tetrahedra and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.04–2.19 Å. In the tenth W4+ site, W4+ is bonded to six O2- atoms to form distorted WO6 octahedra that share corners with two equivalent WO4 tetrahedra and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.23 Å. In the eleventh W4+ site, W4+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent WO4 tetrahedra and edges with five WO6 octahedra. There are a spread of W–O bond distances ranging from 2.04–2.20 Å. In the twelfth W4+ site, W4+ is bonded to four O2- atoms to form corner-sharing WO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–61°. There are three shorter (1.99 Å) and one longer (2.02 Å) W–O bond lengths. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two W4+ atoms. In the second O2- site, O2- is bonded in a water-like geometry to two W4+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three W4+ atoms. In the fourth O2- site, O2- is bonded in a water-like geometry to two W4+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the sixth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three W4+ atoms. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four W4+ atoms. In the eighth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three W4+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the twelfth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three W4+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to three W4+ atoms. In the fifteenth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three W4+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three W4+ atoms. In the twentieth O2- site, O2- is bonded in a 3-coordinate geometry to three W4+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted trigonal planar geometry to three W4+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted trigonal planar geometry to three W4+ atoms. In the twenty-third O2- site, O2- is bonded in a trigonal non-coplanar geometry to three W4+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three W4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(WO2)2 by Materials Project

Zn(WO2)2 is beta indium sulfide-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent ZnO4 tetrahedra, corners with four WO4 trigonal pyramids, edges with three WO6 octahedra, and edges with three ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.23 Å. In the second W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six WO6 octahedra and corners with six ZnO6 octahedra. The corner-sharing octahedra tilt angles range from 42–65°. There are a spread of W–O bond distances ranging from 2.03–2.29 Å. In the third W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent ZnO4 tetrahedra, corners with three equivalent WO4 trigonal pyramids, edges with two ZnO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.11–2.21 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent ZnO4 tetrahedra, corners with four WO4 trigonal pyramids, edges with three WO6 octahedra, and edges with three ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.07–2.19 Å. In the fifth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.12–2.22 Å. In the sixth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are two shorter (2.00 Å) and one longer (2.04 Å) W–O bond lengths. In the seventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.12–2.24 Å. In the eighth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one ZnO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three WO6 octahedra, and edges with three ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.22 Å. In the ninth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six WO6 octahedra and corners with six ZnO6 octahedra. The corner-sharing octahedra tilt angles range from 37–69°. There are a spread of W–O bond distances ranging from 2.00–2.48 Å. In the tenth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one ZnO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three WO6 octahedra, and edges with three ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.24 Å. In the eleventh W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. All W–O bond lengths are 2.02 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with three ZnO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 47–72°. There are a spread of W–O bond distances ranging from 2.07–2.38 Å. There are six inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four O2- atoms to form ZnO4 tetrahedra that share corners with three ZnO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–65°. There are a spread of Zn–O bond distances ranging from 2.04–2.16 Å. In the second Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with six WO4 trigonal pyramids, edges with two ZnO6 octahedra, and edges with four WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.07–2.29 Å. In the third Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with two equivalent ZnO4 tetrahedra, corners with four WO4 trigonal pyramids, an edgeedge with one ZnO6 octahedra, and edges with five WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.09–2.29 Å. In the fourth Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share edges with two ZnO6 octahedra and edges with four WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.08–2.22 Å. In the fifth Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two ZnO6 octahedra, and edges with four WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.03–2.27 Å. In the sixth Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share a cornercorner with one ZnO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one ZnO6 octahedra, and edges with five WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.02–2.36 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to two W3+ and one Zn2+ atom. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the tenth O2- site, O2- is bonded to three W3+ and one Zn2+ atom to form distorted corner-sharing OZnW3 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted tetrahedral geometry to three W3+ and one Zn2+ atom. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the twenty-first O2- site, O2- is bonded to four W3+ atoms to form distorted corner-sharing OW4 tetrahedra. In the twenty-second O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the twenty-third O2- site, O2- is bonded in a 3-coordinate geometry to two W3+ and one Zn2+ atom. In the twenty-fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(WO2)2 by Materials Project

Ca(WO2)2 is beta indium sulfide-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 54–67°. There are three shorter (2.28 Å) and one longer (2.35 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three equivalent WO4 trigonal pyramids, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.27–2.42 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.31–2.42 Å. In the fourth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three equivalent WO4 trigonal pyramids, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.30–2.41 Å. In the fifth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two WO4 trigonal pyramids, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.22–2.49 Å. In the sixth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with two equivalent WO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.27–2.41 Å. There are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.21 Å. In the second W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of W–O bond distances ranging from 1.97–2.07 Å. In the third W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent CaO4 tetrahedra, corners with three equivalent WO4 tetrahedra, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.06–2.27 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.18–2.24 Å. In the fifth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four CaO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.24 Å. In the sixth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 39–70°. There are a spread of W–O bond distances ranging from 1.97–2.36 Å. In the seventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four CaO6 octahedra. There are a spread of W–O bond distances ranging from 2.00–2.23 Å. In the eighth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with two equivalent WO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.22 Å. In the ninth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 43–79°. There are a spread of W–O bond distances ranging from 2.07–2.35 Å. In the tenth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with two equivalent WO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.26 Å. In the eleventh W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of W–O bond distances ranging from 1.97–2.04 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form distorted WO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 51–75°. There are a spread of W–O bond distances ranging from 2.04–2.53 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the third O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 tetrahedra that share corners with two OCa2W2 tetrahedra, corners with four OCaW3 trigonal pyramids, and an edgeedge with one OCaW3 tetrahedra. In the fourth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 tetrahedra that share corners with two OCa2W2 tetrahedra, corners with four OCaW3 trigonal pyramids, and an edgeedge with one OCa2W2 tetrahedra. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the ninth O2- site, O2- is bonded in a trigonal non-coplanar geometry to two Ca2+ and one W3+ atom. In the tenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form OCaW3 trigonal pyramids that share corners with four OCa2W2 tetrahedra and corners with two OCaW3 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one W3+ atom. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the seventeenth O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 tetrahedra that share corners with two OCa2W2 tetrahedra and corners with four OCaW3 trigonal pyramids. In the eighteenth O2- site, O2- is bonded in a trigonal pyramidal geometry to one Ca2+ and three W3+ atoms. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four W3+ atoms. In the twenty-second O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 trigonal pyramids that share corners with four OCa2W2 tetrahedra, corners with two OCaW3 trigonal pyramids, and an edgeedge with one OCaW3 trigonal pyramid. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twenty-fourth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 trigonal pyramids that share corners with four OCa2W2 tetrahedra, corners with two OCaW3 trigonal pyramids, and an edgeedge with one OCaW3 trigonal pyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(WO2)2 by Materials Project

Ca(WO2)2 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 58–61°. There are a spread of Ca–O bond distances ranging from 2.20–2.32 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three CaO4 tetrahedra, corners with three WO4 tetrahedra, and edges with six WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.30–2.36 Å. In the third Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 56–65°. There are a spread of Ca–O bond distances ranging from 2.22–2.32 Å. In the fourth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two equivalent CaO4 tetrahedra, corners with four WO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.29–2.44 Å. In the fifth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six WO4 tetrahedra, edges with two CaO6 octahedra, and edges with four equivalent WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.35–2.39 Å. In the sixth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six WO4 tetrahedra, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.31–2.42 Å. In the seventh Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with five WO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.28–2.38 Å. In the eighth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six WO4 tetrahedra, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.41 Å. There are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three CaO4 tetrahedra, corners with three WO4 tetrahedra, edges with two equivalent CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.26 Å. In the second W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent CaO4 tetrahedra, corners with three equivalent WO4 tetrahedra, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.29 Å. In the third W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 49–67°. There are a spread of W–O bond distances ranging from 2.02–2.07 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent CaO4 tetrahedra, corners with four WO4 tetrahedra, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.26 Å. In the fifth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–66°. There are a spread of W–O bond distances ranging from 2.08–2.16 Å. In the sixth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–73°. There are a spread of W–O bond distances ranging from 2.14–2.19 Å. In the seventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six WO4 tetrahedra, edges with two equivalent WO6 octahedra, and edges with four CaO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.24 Å. In the eighth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 53–70°. There are a spread of W–O bond distances ranging from 2.12–2.20 Å. In the ninth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with five WO4 tetrahedra, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.24 Å. In the tenth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 48–70°. There are one shorter (2.04 Å) and three longer (2.09 Å) W–O bond lengths. In the eleventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent CaO4 tetrahedra, corners with three equivalent WO4 tetrahedra, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.23 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of W–O bond distances ranging from 2.07–2.38 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Ca2+ and two equivalent W3+ atoms. In the third O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 trigonal pyramids that share a cornercorner with one OW4 tetrahedra and a cornercorner with one OCa2W2 trigonal pyramid. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four W3+ atoms. In the fifth O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 trigonal pyramids that share a cornercorner with one OCaW3 tetrahedra, a cornercorner with one OCa2W2 trigonal pyramid, an edgeedge with one OCaW3 tetrahedra, and an edgeedge with one OCa2W2 trigonal pyramid. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the ninth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form a mixture of distorted corner and edge-sharing OCaW3 tetrahedra. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the thirteenth O2- site, O2- is bonded in a trigonal pyramidal geometry to one Ca2+ and three W3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the nineteenth O2- site, O2- is bonded to two Ca2+ and two equivalent W3+ atoms to form distorted OCa2W2 trigonal pyramids that share corners with two equivalent OW4 tetrahedra and a cornercorner with one OCaW3 trigonal pyramid. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twenty-second O2- site, O2- is bonded to four W3+ atoms to form distorted corner-sharing OW4 tetrahedra. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(WO2)2 by Materials Project

Zn(WO2)2 is Ilmenite-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent WO4 tetrahedra, corners with three ZnO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, edges with two equivalent ZnO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.23 Å. In the second W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent WO4 tetrahedra, corners with three equivalent ZnO4 tetrahedra, edges with two ZnO6 octahedra, and edges with four WO6 octahedra. There are two shorter (2.16 Å) and four longer (2.18 Å) W–O bond lengths. In the third W3+ site, W3+ is bonded to four O2- atoms to form distorted WO4 trigonal pyramids that share corners with six WO6 octahedra and corners with six ZnO6 octahedra. The corner-sharing octahedra tilt angles range from 37–80°. There are a spread of W–O bond distances ranging from 2.00–2.48 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent ZnO4 tetrahedra, corners with three WO4 trigonal pyramids, edges with three WO6 octahedra, and edges with three ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.12–2.20 Å. In the fifth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with three ZnO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 51–73°. There are a spread of W–O bond distances ranging from 2.04–2.29 Å. In the sixth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are two shorter (2.02 Å) and one longer (2.10 Å) W–O bond lengths. In the seventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.11–2.23 Å. In the eighth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six WO6 octahedra and corners with six ZnO6 octahedra. The corner-sharing octahedra tilt angles range from 23–82°. There are a spread of W–O bond distances ranging from 2.01–2.51 Å. In the ninth W3+ site, W3+ is bonded to six O2- atoms to form distorted WO6 octahedra that share a cornercorner with one ZnO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three WO6 octahedra, and edges with three ZnO6 octahedra. There are a spread of W–O bond distances ranging from 2.11–2.35 Å. In the tenth W3+ site, W3+ is bonded in a distorted trigonal planar geometry to three O2- atoms. There are two shorter (2.02 Å) and one longer (2.04 Å) W–O bond lengths. In the eleventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent ZnO4 tetrahedra, corners with three equivalent WO4 trigonal pyramids, edges with two ZnO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.11–2.20 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with three ZnO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 35–76°. There are a spread of W–O bond distances ranging from 2.02–2.32 Å. There are eight inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four O2- atoms to form ZnO4 tetrahedra that share corners with three ZnO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 51–63°. There are a spread of Zn–O bond distances ranging from 2.02–2.06 Å. In the second Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with two equivalent WO4 tetrahedra, corners with three ZnO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, and edges with six WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.11–2.23 Å. In the third Zn2+ site, Zn2+ is bonded to four O2- atoms to form ZnO4 tetrahedra that share corners with three ZnO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 49–59°. There are a spread of Zn–O bond distances ranging from 2.00–2.09 Å. In the fourth Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent ZnO4 tetrahedra, corners with three WO4 trigonal pyramids, an edgeedge with one ZnO6 octahedra, and edges with five WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.11–2.27 Å. In the fifth Zn2+ site, Zn2+ is bonded to six O2- atoms to form distorted ZnO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two ZnO6 octahedra, and edges with four equivalent WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.05–2.14 Å. In the sixth Zn2+ site, Zn2+ is bonded to six O2- atoms to form distorted ZnO6 octahedra that share corners with six WO4 trigonal pyramids, edges with two ZnO6 octahedra, and edges with four WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.01–2.57 Å. In the seventh Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share a cornercorner with one ZnO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one ZnO6 octahedra, and edges with five WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.10–2.28 Å. In the eighth Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share edges with two ZnO6 octahedra and edges with four WO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.06–2.20 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent W3+ and two Zn2+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the fourth O2- site, O2- is bonded to four W3+ atoms to form a mixture of distorted corner and edge-sharing OW4 trigonal pyramids. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the eighth O2- site, O2- is bonded to three W3+ and one Zn2+ atom to form distorted OZnW3 trigonal pyramids that share corners with two equivalent OZnW3 trigonal pyramids and an edgeedge with one OW4 trigonal pyramid. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the tenth O2- site, O2- is bonded to two W3+ and two Zn2+ atoms to form distorted OZn2W2 trigonal pyramids that share a cornercorner with one OZnW3 tetrahedra, corners with six OZn2W2 trigonal pyramids, and an edgeedge with one OZn2W2 trigonal pyramid. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to three W3+ and one Zn2+ atom. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two W3+ and two Zn2+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent W3+ and one Zn2+ atom. In the fourteenth O2- site, O2- is bonded to three W3+ and one Zn2+ atom to form distorted corner-sharing OZnW3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three W3+ and one Zn2+ atom. In the sixteenth O2- site, O2- is bonded to three W3+ and one Zn2+ atom to form distorted OZnW3 tetrahedra that share a cornercorner with one OZnW3 tetrahedra, corners with six OZn2W2 trigonal pyramids, and edges with three OZnW3 trigonal pyramids. In the seventeenth O2- site, O2- is bonded to two W3+ and two Zn2+ atoms to form distorted OZn2W2 trigonal pyramids that share corners with two OZnW3 tetrahedra, corners with six OZn2W2 trigonal pyramids, edges with two OZnW3 tetrahedra, and an edgeedge with one OZn2W2 trigonal pyramid. In the eighteenth O2- site, O2- is bonded to two W3+ and two Zn2+ atoms to form distorted OZn2W2 trigonal pyramids that share corners with two OZnW3 tetrahedra, corners with six OZn2W2 trigonal pyramids, an edgeedge with one OZnW3 tetrahedra, and edges with two OZnW3 trigonal pyramids. In the nineteenth O2- site, O2- is bonded to two equivalent W3+ and two Zn2+ atoms to form distorted OZn2W2 tetrahedra that share corners with four equivalent OZnW3 trigonal pyramids, an edgeedge with one OZnW3 tetrahedra, and edges with two equivalent OZn2W2 trigonal pyramids. In the twentieth O2- site, O2- is bonded to three W3+ and one Zn2+ atom to form distorted OZnW3 trigonal pyramids that share corners with four equivalent OZn2W2 trigonal pyramids, an edgeedge with one OZnW3 tetrahedra, and edges with two equivalent OZn2W2 trigonal pyramids. In the twenty-first O2- site, O2- is bonded to three W3+ and one Zn2+ atom to form distorted OZnW3 tetrahedra that share a cornercorner with one OZnW3 tetrahedra, corners with six OZn2W2 trigonal pyramids, an edgeedge with one OZn2W2 tetrahedra, and edges with two equivalent OZn2W2 trigonal pyramids. In the twenty-second O2- site, O2- is bonded in a 4-coordinate geometry to four W3+ atoms. In the twenty-third O2- site, O2- is bonded to three W3+ and one Zn2+ atom to form OZnW3 trigonal pyramids that share corners with three OZn2W2 tetrahedra, corners with five OZn2W2 trigonal pyramids, and an edgeedge with one OZnW3 trigonal pyramid. In the twenty-fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent W3+ and one Zn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(WO2)2 by Materials Project

Mg(WO2)2 is beta indium sulfide-derived structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 50–62°. There are a spread of Mg–O bond distances ranging from 2.02–2.06 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent WO4 tetrahedra, corners with three MgO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, and edges with six WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.12–2.18 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–64°. There are a spread of Mg–O bond distances ranging from 2.06–2.13 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent MgO4 tetrahedra, corners with three WO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.12–2.17 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four equivalent WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.16 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.19 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.24 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share edges with two MgO6 octahedra and edges with four WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.11–2.17 Å. There are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent WO4 tetrahedra, corners with three MgO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, edges with two equivalent MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.21 Å. In the second W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent WO4 tetrahedra, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.18–2.22 Å. In the third W3+ site, W3+ is bonded to four O2- atoms to form distorted WO4 trigonal pyramids that share corners with six MgO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 39–71°. There are a spread of W–O bond distances ranging from 2.03–2.31 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent MgO4 tetrahedra, corners with three WO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.24 Å. In the fifth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–69°. There are a spread of W–O bond distances ranging from 2.09–2.22 Å. In the sixth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are two shorter (2.01 Å) and one longer (2.04 Å) W–O bond lengths. In the seventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four MgO6 octahedra. There are a spread of W–O bond distances ranging from 2.11–2.23 Å. In the eighth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six MgO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 37–70°. There are a spread of W–O bond distances ranging from 2.01–2.27 Å. In the ninth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.13–2.22 Å. In the tenth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are two shorter (2.02 Å) and one longer (2.03 Å) W–O bond lengths. In the eleventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.06–2.11 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 46–70°. There are a spread of W–O bond distances ranging from 2.11–2.29 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent W3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four W3+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent W3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three W3+ atoms to form distorted corner-sharing OMgW3 tetrahedra. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent W3+ atoms. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the twenty-first O2- site, O2- is bonded to one Mg2+ and three W3+ atoms to form distorted corner-sharing OMgW3 tetrahedra. In the twenty-second O2- site, O2- is bonded to four W3+ atoms to form distorted corner-sharing OW4 tetrahedra. In the twenty-third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent W3+ atoms.

36 MATERIALS SCIENCE↗