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DOE OSTI2020

Materials Data on Nb3Os by Materials Project

Nb3Os is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded to four equivalent Nb and four equivalent Os atoms to form a mixture of distorted corner, edge, and face-sharing NbNb4Os4 tetrahedra. All Nb–Nb bond lengths are 2.81 Å. All Nb–Os bond lengths are 2.81 Å. In the second Nb site, Nb is bonded in a 8-coordinate geometry to eight equivalent Nb and six equivalent Os atoms. All Nb–Os bond lengths are 3.24 Å. Os is bonded in a distorted body-centered cubic geometry to fourteen Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb8N5 by Materials Project

Nb8N5 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a T-shaped geometry to three N atoms. There are two shorter (2.20 Å) and one longer (2.21 Å) Nb–N bond lengths. In the second Nb site, Nb is bonded in a square co-planar geometry to four equivalent N atoms. All Nb–N bond lengths are 2.18 Å. In the third Nb site, Nb is bonded to five N atoms to form a mixture of edge and corner-sharing NbN5 square pyramids. There are four shorter (2.20 Å) and one longer (2.22 Å) Nb–N bond lengths. There are two inequivalent N sites. In the first N site, N is bonded to six Nb atoms to form edge-sharing NNb6 octahedra. In the second N site, N is bonded to six Nb atoms to form a mixture of edge and corner-sharing NNb6 octahedra. The corner-sharing octahedra tilt angles range from 1–2°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3WSe8 by Materials Project

NbWSe4(NbSe2)2 is Molybdenite-derived structured and crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of two NbSe2 sheets oriented in the (1, 0, 0) direction and two NbWSe4 sheets oriented in the (1, 0, 0) direction. In each NbSe2 sheet, Nb+4.67+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. There are a spread of Nb–Se bond distances ranging from 2.61–2.63 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+4.67+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+4.67+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+4.67+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+4.67+ atoms. In each NbWSe4 sheet, Nb+4.67+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share edges with two equivalent NbSe6 pentagonal pyramids and edges with four equivalent WSe6 pentagonal pyramids. There are four shorter (2.61 Å) and two longer (2.64 Å) Nb–Se bond lengths. W2+ is bonded to six Se2- atoms to form distorted WSe6 pentagonal pyramids that share edges with two equivalent WSe6 pentagonal pyramids and edges with four equivalent NbSe6 pentagonal pyramids. There are two shorter (2.56 Å) and four longer (2.59 Å) W–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent Nb+4.67+ and one W2+ atom. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to one Nb+4.67+ and two equivalent W2+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to one Nb+4.67+ and two equivalent W2+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent Nb+4.67+ and one W2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaNb6HO16 by Materials Project

(BaNb6O16)2H2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional and consists of two hydrogen molecules and one BaNb6O16 framework. In the BaNb6O16 framework, Ba2+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Ba–O bond lengths are 2.85 Å. There are two inequivalent Nb+4.83+ sites. In the first Nb+4.83+ site, Nb+4.83+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.80–2.49 Å. In the second Nb+4.83+ site, Nb+4.83+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.83–2.37 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two Nb+4.83+ atoms. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Nb+4.83+ atoms. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ba2+ and one Nb+4.83+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to three Nb+4.83+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to four Nb+4.83+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb6HI11 by Materials Project

HNb6I11 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are six inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded to one H1- and five I1- atoms to form a mixture of distorted corner and face-sharing NbHI5 octahedra. The corner-sharing octahedra tilt angles range from 4–26°. The Nb–H bond length is 2.05 Å. There are a spread of Nb–I bond distances ranging from 2.85–2.99 Å. In the second Nb2+ site, Nb2+ is bonded to one H1- and five I1- atoms to form a mixture of distorted corner and face-sharing NbHI5 octahedra. The corner-sharing octahedra tilt angles range from 4–26°. The Nb–H bond length is 2.06 Å. There are a spread of Nb–I bond distances ranging from 2.87–2.99 Å. In the third Nb2+ site, Nb2+ is bonded to one H1- and five I1- atoms to form a mixture of distorted corner and face-sharing NbHI5 octahedra. The corner-sharing octahedra tilt angles range from 3–53°. The Nb–H bond length is 2.08 Å. There are a spread of Nb–I bond distances ranging from 2.87–3.03 Å. In the fourth Nb2+ site, Nb2+ is bonded to one H1- and five I1- atoms to form a mixture of distorted corner and face-sharing NbHI5 octahedra. The corner-sharing octahedra tilt angles range from 3–54°. The Nb–H bond length is 2.04 Å. There are a spread of Nb–I bond distances ranging from 2.85–2.99 Å. In the fifth Nb2+ site, Nb2+ is bonded to one H1- and five I1- atoms to form a mixture of distorted corner and face-sharing NbHI5 octahedra. The corner-sharing octahedra tilt angles range from 4–53°. The Nb–H bond length is 2.05 Å. There are a spread of Nb–I bond distances ranging from 2.86–2.99 Å. In the sixth Nb2+ site, Nb2+ is bonded to one H1- and five I1- atoms to form a mixture of distorted corner and face-sharing NbHI5 octahedra. The corner-sharing octahedra tilt angles range from 4–54°. The Nb–H bond length is 2.02 Å. There are a spread of Nb–I bond distances ranging from 2.88–2.95 Å. H1- is bonded in an octahedral geometry to six Nb2+ atoms. There are eleven inequivalent I1- sites. In the first I1- site, I1- is bonded in a 5-coordinate geometry to three Nb2+ atoms. In the second I1- site, I1- is bonded in a bent 120 degrees geometry to two Nb2+ atoms. In the third I1- site, I1- is bonded in a 4-coordinate geometry to three Nb2+ atoms. In the fourth I1- site, I1- is bonded in a bent 150 degrees geometry to two Nb2+ atoms. In the fifth I1- site, I1- is bonded in a 5-coordinate geometry to three Nb2+ atoms. In the sixth I1- site, I1- is bonded in a 12-coordinate geometry to three Nb2+ atoms. In the seventh I1- site, I1- is bonded in a bent 120 degrees geometry to two Nb2+ atoms. In the eighth I1- site, I1- is bonded in a 5-coordinate geometry to three Nb2+ atoms. In the ninth I1- site, I1- is bonded in a 4-coordinate geometry to three Nb2+ atoms. In the tenth I1- site, I1- is bonded in a 3-coordinate geometry to three Nb2+ atoms. In the eleventh I1- site, I1- is bonded in a 6-coordinate geometry to three Nb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb2CuCS2 by Materials Project

Nb2CuCS2 crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are two inequivalent Nb+3.50+ sites. In the first Nb+3.50+ site, Nb+3.50+ is bonded to three equivalent C4- and three equivalent S2- atoms to form a mixture of edge and corner-sharing NbC3S3 octahedra. The corner-sharing octahedral tilt angles are 1°. All Nb–C bond lengths are 2.23 Å. All Nb–S bond lengths are 2.61 Å. In the second Nb+3.50+ site, Nb+3.50+ is bonded to three equivalent C4- and three equivalent S2- atoms to form a mixture of edge and corner-sharing NbC3S3 octahedra. The corner-sharing octahedral tilt angles are 1°. All Nb–C bond lengths are 2.26 Å. All Nb–S bond lengths are 2.54 Å. Cu1+ is bonded in a distorted rectangular see-saw-like geometry to four S2- atoms. There are one shorter (2.20 Å) and three longer (2.32 Å) Cu–S bond lengths. C4- is bonded to six Nb+3.50+ atoms to form edge-sharing CNb6 octahedra. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three equivalent Nb+3.50+ and one Cu1+ atom. In the second S2- site, S2- is bonded in a 6-coordinate geometry to three equivalent Nb+3.50+ and three equivalent Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2Nb4Cu(ClO7)2 by Materials Project

La2Nb4Cu(O7Cl)2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. La is bonded to twelve O atoms to form a mixture of face and corner-sharing LaO12 cuboctahedra. There are eight shorter (2.68 Å) and four longer (2.77 Å) La–O bond lengths. There are two inequivalent Nb sites. In the first Nb site, Nb is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Nb–O bond distances ranging from 1.82–2.30 Å. In the second Nb site, Nb is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Nb–O bond distances ranging from 1.76–2.35 Å. Cu is bonded in a distorted linear geometry to two equivalent O and four equivalent Cl atoms. Both Cu–O bond lengths are 1.82 Å. All Cu–Cl bond lengths are 2.77 Å. There are five inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to two equivalent La and two Nb atoms. In the second O site, O is bonded in a linear geometry to one Nb and one Cu atom. In the third O site, O is bonded in a single-bond geometry to one Nb atom. In the fourth O site, O is bonded to four equivalent La and two equivalent Nb atoms to form a mixture of edge and corner-sharing OLa4Nb2 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O site, O is bonded to four equivalent La and two equivalent Nb atoms to form a mixture of edge and corner-sharing OLa4Nb2 octahedra. The corner-sharing octahedral tilt angles are 0°. Cl is bonded in a linear geometry to two equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3(IrSe5)2 by Materials Project

Nb3(IrSe5)2 is Calaverite-derived structured and crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one Nb3(IrSe5)2 sheet oriented in the (0, 1, -1) direction. there are two inequivalent Nb+4.67+ sites. In the first Nb+4.67+ site, Nb+4.67+ is bonded to six Se2- atoms to form distorted NbSe6 octahedra that share edges with three NbSe6 octahedra and edges with three equivalent IrSe6 octahedra. There are a spread of Nb–Se bond distances ranging from 2.52–2.80 Å. In the second Nb+4.67+ site, Nb+4.67+ is bonded to six Se2- atoms to form NbSe6 octahedra that share edges with two equivalent NbSe6 octahedra and edges with four equivalent IrSe6 octahedra. There are a spread of Nb–Se bond distances ranging from 2.58–2.68 Å. Ir3+ is bonded to six Se2- atoms to form IrSe6 octahedra that share an edgeedge with one IrSe6 octahedra and edges with five NbSe6 octahedra. There are a spread of Ir–Se bond distances ranging from 2.52–2.59 Å. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.67+ and one Ir3+ atom. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to two Nb+4.67+ and one Ir3+ atom. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent Nb+4.67+ and one Ir3+ atom. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to one Nb+4.67+ and two equivalent Ir3+ atoms. In the fifth Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent Nb+4.67+ and one Ir3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Formation and Microwave Losses of Hydrides in Superconducting Niobium Thin Films Resulting from Fluoride Chemical Processing

Abstract Superconducting niobium (Nb) thin films have recently attracted significant attention due to their utility for quantum information technologies. In the processing of Nb thin films, fluoride‐based chemical etchants are commonly used to remove surface oxides that are known to affect superconducting quantum devices adversely. However, these same etchants can also introduce hydrogen to form Nb hydrides, potentially negatively impacting microwave loss performance. Here, comprehensive materials characterization of Nb hydrides formed in Nb thin films as a function of fluoride chemical treatments is presented. In particular, secondary‐ion mass spectrometry, X‐ray scattering, and transmission electron microscopy reveal the spatial distribution and phase transformation of Nb hydrides. The rate of hydride formation is determined by the fluoride solution acidity and the etch rate of Nb 2 O 5, which acts as a diffusion barrier for hydrogen into Nb. The resulting Nb hydrides are detrimental to Nb superconducting properties and lead to increased power‐independent microwave loss in coplanar waveguide resonators. However, Nb hydrides do not correlate with two‐level system loss or device aging mechanisms. Overall, this work provides insight into the formation of Nb hydrides and their role in microwave loss, thus guiding ongoing efforts to maximize coherence time in superconducting quantum devices.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Nb3Sn Superconducting Radiofrequency Cavity Fabricated by Sputter Deposition from a Stoichiometric Target

Nb$_3$Sn is a promising coating material for superconducting radiofrequency cavities in next-generation accelerators due to its higher superconducting transition temperature (~18.3 K) and superheating field (~400 mT), offering the potential to surpass the intrinsic performance limits of bulk niobium. We developed a sputter coating technique employing a stoichiometric target to fabricate Nb$_3$Sn films on the inner surfaces of niobium cavities. A Nb$_3$Sn tube target, prepared by growing a >20 m thick Nb$_3$Sn coating on the surface of a Nb tube via a Sn vapor diffusion process, was used in a DC cylindrical magnetron sputtering system. Approximately 170 nm thick Nb-Sn films were sputter-coated onto flat Nb substrates positioned to replicate the beam tube and equator regions of a 2.6 GHz cavity, followed by annealing at 950 °C for 3 hours to form Nb$_3$Sn. The composition, morphology, and structure of the annealed Nb$_3$Sn films were examined. Then, a ~1.2 m-thick film was sputter-coated onto the interior of a 2.6 GHz Nb cavity following the procedure developed for the flat samples. The cavity was subsequently annealed under the same conditions used for the flat samples. Cryogenic RF testing of the sputter-coated cavity demonstrated a T$_c$ of approximately 17.8 K, consistent with Nb$_3$Sn layer. Subsequently, the cavity underwent a light Sn recoating followed by a vapor diffusion Nb$_3$Sn coating process, achieving a quality factor of approximately 8.5 × 10$^9$ and an accelerating gradient of up to 11.3 MV/m at 4.2 K.

Shakel, Md Sharifuzzaman [Old Dominion U.; Jeffers↗
DOE OSTI2020

Materials Data on Nb3Si by Materials Project

Nb3Si crystallizes in the tetragonal P4_2/n space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 2-coordinate geometry to two equivalent Si atoms. There are one shorter (2.62 Å) and one longer (2.66 Å) Nb–Si bond lengths. In the second Nb site, Nb is bonded in a 4-coordinate geometry to four equivalent Si atoms. There are a spread of Nb–Si bond distances ranging from 2.60–2.72 Å. In the third Nb site, Nb is bonded in a 2-coordinate geometry to three equivalent Si atoms. There are a spread of Nb–Si bond distances ranging from 2.59–2.87 Å. Si is bonded in a 9-coordinate geometry to nine Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Se12I by Materials Project

(NbSe4)3I crystallizes in the tetragonal P4/mnc space group. The structure is three-dimensional. there are two inequivalent Nb+4.33+ sites. In the first Nb+4.33+ site, Nb+4.33+ is bonded in a 8-coordinate geometry to eight Se1- atoms. There are four shorter (2.60 Å) and four longer (2.77 Å) Nb–Se bond lengths. In the second Nb+4.33+ site, Nb+4.33+ is bonded to eight Se1- atoms to form distorted face-sharing NbSe8 hexagonal bipyramids. There are a spread of Nb–Se bond distances ranging from 2.66–2.75 Å. There are four inequivalent Se1- sites. In the first Se1- site, Se1- is bonded in a 2-coordinate geometry to two Nb+4.33+ atoms. In the second Se1- site, Se1- is bonded in a 2-coordinate geometry to two equivalent Nb+4.33+ and one Se1- atom. The Se–Se bond length is 2.36 Å. In the third Se1- site, Se1- is bonded in a 2-coordinate geometry to two equivalent Nb+4.33+, one Se1-, and two equivalent I1- atoms. Both Se–I bond lengths are 4.06 Å. In the fourth Se1- site, Se1- is bonded in a 2-coordinate geometry to two Nb+4.33+ and one I1- atom. The Se–I bond length is 3.39 Å. I1- is bonded in a 4-coordinate geometry to eight Se1- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Co4B7 by Materials Project

Nb3Co4B7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Nb+2.33+ sites. In the first Nb+2.33+ site, Nb+2.33+ is bonded to eight B+2.14- atoms to form NbB8 hexagonal bipyramids that share corners with four equivalent CoB4 tetrahedra, edges with six equivalent CoB4 tetrahedra, and faces with two equivalent NbB8 hexagonal bipyramids. There are four shorter (2.46 Å) and four longer (2.51 Å) Nb–B bond lengths. In the second Nb+2.33+ site, Nb+2.33+ is bonded in a distorted q4 geometry to nine B+2.14- atoms. There are a spread of Nb–B bond distances ranging from 2.40–2.51 Å. There are three inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded in a 10-coordinate geometry to ten B+2.14- atoms. There are a spread of Co–B bond distances ranging from 2.18–2.26 Å. In the second Co2+ site, Co2+ is bonded in a 5-coordinate geometry to five B+2.14- atoms. There are one shorter (2.05 Å) and four longer (2.10 Å) Co–B bond lengths. In the third Co2+ site, Co2+ is bonded to four B+2.14- atoms to form CoB4 tetrahedra that share corners with two equivalent NbB8 hexagonal bipyramids, corners with two equivalent CoB4 tetrahedra, edges with three equivalent NbB8 hexagonal bipyramids, and edges with two equivalent CoB4 tetrahedra. There are two shorter (2.08 Å) and two longer (2.09 Å) Co–B bond lengths. There are four inequivalent B+2.14- sites. In the first B+2.14- site, B+2.14- is bonded in a 9-coordinate geometry to three Nb+2.33+, five Co2+, and one B+2.14- atom. The B–B bond length is 1.87 Å. In the second B+2.14- site, B+2.14- is bonded in a 9-coordinate geometry to four equivalent Nb+2.33+, two equivalent Co2+, and three B+2.14- atoms. There are a spread of B–B bond distances ranging from 1.75–1.80 Å. In the third B+2.14- site, B+2.14- is bonded in a 9-coordinate geometry to four equivalent Nb+2.33+, three Co2+, and two equivalent B+2.14- atoms. In the fourth B+2.14- site, B+2.14- is bonded in a 9-coordinate geometry to four Nb+2.33+, three Co2+, and two B+2.14- atoms. The B–B bond length is 1.82 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3As by Materials Project

Nb3As crystallizes in the tetragonal P4_2/n space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 2-coordinate geometry to four equivalent As atoms. There are a spread of Nb–As bond distances ranging from 2.51–2.95 Å. In the second Nb site, Nb is bonded in a 2-coordinate geometry to three equivalent As atoms. There are a spread of Nb–As bond distances ranging from 2.60–2.92 Å. In the third Nb site, Nb is bonded in a distorted bent 150 degrees geometry to two equivalent As atoms. There are one shorter (2.60 Å) and one longer (2.62 Å) Nb–As bond lengths. As is bonded in a 9-coordinate geometry to nine Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3P by Materials Project

Nb3P crystallizes in the tetragonal P4_2/n space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a distorted bent 150 degrees geometry to two equivalent P atoms. There are one shorter (2.59 Å) and one longer (2.62 Å) Nb–P bond lengths. In the second Nb site, Nb is bonded in a 4-coordinate geometry to four equivalent P atoms. There are a spread of Nb–P bond distances ranging from 2.57–2.66 Å. In the third Nb site, Nb is bonded in a 2-coordinate geometry to three equivalent P atoms. There are a spread of Nb–P bond distances ranging from 2.56–2.91 Å. P is bonded in a 9-coordinate geometry to nine Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KNb4O5F by Materials Project

KNb4O5F crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded to eight equivalent O2- and four equivalent F1- atoms to form KO8F4 cuboctahedra that share corners with four equivalent KO8F4 cuboctahedra, faces with four equivalent KO8F4 cuboctahedra, and faces with eight equivalent NbO4F square pyramids. All K–O bond lengths are 3.01 Å. All K–F bond lengths are 2.98 Å. There are two inequivalent Nb+2.50+ sites. In the first Nb+2.50+ site, Nb+2.50+ is bonded to four equivalent O2- and one F1- atom to form NbO4F square pyramids that share corners with five equivalent NbO4F square pyramids and faces with four equivalent KO8F4 cuboctahedra. All Nb–O bond lengths are 2.11 Å. The Nb–F bond length is 2.25 Å. In the second Nb+2.50+ site, Nb+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.10 Å) and two longer (2.12 Å) Nb–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to two equivalent K1+ and three Nb+2.50+ atoms. In the second O2- site, O2- is bonded in a square co-planar geometry to four equivalent Nb+2.50+ atoms. F1- is bonded in a distorted linear geometry to four equivalent K1+ and two equivalent Nb+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb2CrSe4 by Materials Project

Nb2CrSe4 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Nb+2.50+ sites. In the first Nb+2.50+ site, Nb+2.50+ is bonded in a 7-coordinate geometry to one Cr3+ and six Se2- atoms. The Nb–Cr bond length is 2.43 Å. There are two shorter (2.59 Å) and four longer (2.79 Å) Nb–Se bond lengths. In the second Nb+2.50+ site, Nb+2.50+ is bonded to six equivalent Se2- atoms to form distorted NbSe6 pentagonal pyramids that share faces with two equivalent CrSe6 octahedra. All Nb–Se bond lengths are 2.62 Å. There are two inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to six equivalent Se2- atoms to form CrSe6 octahedra that share faces with two equivalent NbSe6 pentagonal pyramids. All Cr–Se bond lengths are 2.56 Å. In the second Cr3+ site, Cr3+ is bonded in a 9-coordinate geometry to three equivalent Nb+2.50+ and six equivalent Se2- atoms. All Cr–Se bond lengths are 2.64 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to three Nb+2.50+ and two Cr3+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbPd3 by Materials Project

NbPd3 is beta Cu3Ti-like structured and crystallizes in the orthorhombic Pmmn space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded to twelve Pd atoms to form NbPd12 cuboctahedra that share corners with three NbPd12 cuboctahedra, corners with ten PdNb4Pd8 cuboctahedra, edges with seven NbPd12 cuboctahedra, edges with fourteen PdNb4Pd8 cuboctahedra, faces with five NbPd12 cuboctahedra, and faces with twelve PdNb4Pd8 cuboctahedra. There are a spread of Nb–Pd bond distances ranging from 2.75–2.88 Å. In the second Nb site, Nb is bonded to twelve Pd atoms to form NbPd12 cuboctahedra that share corners with four NbPd12 cuboctahedra, corners with four equivalent PdNb4Pd8 cuboctahedra, edges with eight NbPd12 cuboctahedra, edges with sixteen PdNb4Pd8 cuboctahedra, faces with four equivalent NbPd12 cuboctahedra, and faces with twelve PdNb4Pd8 cuboctahedra. There are a spread of Nb–Pd bond distances ranging from 2.78–2.84 Å. There are four inequivalent Pd sites. In the first Pd site, Pd is bonded to four Nb and eight Pd atoms to form distorted PdNb4Pd8 cuboctahedra that share corners with two equivalent NbPd12 cuboctahedra, corners with thirteen PdNb4Pd8 cuboctahedra, edges with seven NbPd12 cuboctahedra, edges with eleven PdNb4Pd8 cuboctahedra, faces with four NbPd12 cuboctahedra, and faces with fourteen PdNb4Pd8 cuboctahedra. There are a spread of Pd–Pd bond distances ranging from 2.78–2.86 Å. In the second Pd site, Pd is bonded to four Nb and eight Pd atoms to form distorted PdNb4Pd8 cuboctahedra that share corners with twelve PdNb4Pd8 cuboctahedra, edges with eight NbPd12 cuboctahedra, edges with fourteen PdNb4Pd8 cuboctahedra, faces with four NbPd12 cuboctahedra, and faces with twelve PdNb4Pd8 cuboctahedra. There are a spread of Pd–Pd bond distances ranging from 2.78–2.87 Å. In the third Pd site, Pd is bonded to four Nb and eight Pd atoms to form distorted PdNb4Pd8 cuboctahedra that share corners with six PdNb4Pd8 cuboctahedra, corners with eight NbPd12 cuboctahedra, edges with eighteen PdNb4Pd8 cuboctahedra, faces with six NbPd12 cuboctahedra, and faces with eleven PdNb4Pd8 cuboctahedra. In the fourth Pd site, Pd is bonded in a distorted see-saw-like geometry to four Nb and eight Pd atoms.

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