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DOE OSTI2020

Materials Data on Be15(Nb3Ni4)2 by Materials Project

Be15(Nb3Ni4)2 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are three inequivalent Be sites. In the first Be site, Be is bonded in a 12-coordinate geometry to six Be, three equivalent Nb, and three equivalent Ni atoms. There are three shorter (2.19 Å) and three longer (2.32 Å) Be–Be bond lengths. All Be–Nb bond lengths are 2.65 Å. All Be–Ni bond lengths are 2.32 Å. In the second Be site, Be is bonded to four equivalent Be, four equivalent Nb, and four equivalent Ni atoms to form a mixture of distorted corner and face-sharing BeBe4Nb4Ni4 cuboctahedra. All Be–Nb bond lengths are 2.73 Å. All Be–Ni bond lengths are 2.34 Å. In the third Be site, Be is bonded in a body-centered cubic geometry to eight equivalent Ni atoms. All Be–Ni bond lengths are 2.28 Å. Nb is bonded in a 8-coordinate geometry to eight Be, four equivalent Nb, and four equivalent Ni atoms. All Nb–Nb bond lengths are 3.09 Å. All Nb–Ni bond lengths are 2.63 Å. Ni is bonded in a 10-coordinate geometry to seven Be and three equivalent Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaYNb2O7 by Materials Project

CaYNb2O7 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Ca2+ is bonded to eight O2- atoms to form distorted CaO8 hexagonal bipyramids that share edges with two equivalent CaO8 hexagonal bipyramids, edges with four equivalent YO8 hexagonal bipyramids, and edges with six NbO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.30–2.64 Å. Y3+ is bonded to eight O2- atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent YO8 hexagonal bipyramids, edges with four equivalent CaO8 hexagonal bipyramids, and edges with six NbO6 octahedra. There are two shorter (2.24 Å) and six longer (2.53 Å) Y–O bond lengths. There are two inequivalent Nb+4.50+ sites. In the first Nb+4.50+ site, Nb+4.50+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra, edges with two equivalent CaO8 hexagonal bipyramids, and edges with four equivalent YO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 49–54°. All Nb–O bond lengths are 2.05 Å. In the second Nb+4.50+ site, Nb+4.50+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra, edges with two equivalent YO8 hexagonal bipyramids, and edges with four equivalent CaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 43–49°. There are two shorter (2.01 Å) and four longer (2.02 Å) Nb–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Ca2+ and two equivalent Y3+ atoms to form OCa2Y2 tetrahedra that share corners with six OCa2Y2 tetrahedra and an edgeedge with one OY2Nb2 tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Nb+4.50+ atoms. In the third O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Nb+4.50+ atoms to form a mixture of distorted edge and corner-sharing OY2Nb2 tetrahedra. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Y3+, and two Nb+4.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2Nb3Ge4 by Materials Project

Y2Nb3Ge4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Y is bonded in a 7-coordinate geometry to seven Ge atoms. There are a spread of Y–Ge bond distances ranging from 2.87–3.09 Å. There are two inequivalent Nb sites. In the first Nb site, Nb is bonded to six Ge atoms to form distorted corner-sharing NbGe6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Nb–Ge bond distances ranging from 2.75–2.88 Å. In the second Nb site, Nb is bonded in a 6-coordinate geometry to six Ge atoms. There are a spread of Nb–Ge bond distances ranging from 2.65–2.80 Å. There are three inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Y, four Nb, and one Ge atom. The Ge–Ge bond length is 2.64 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to two equivalent Y, six Nb, and one Ge atom. In the third Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Y, four Nb, and one Ge atom. The Ge–Ge bond length is 2.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2NbO3F5 by Materials Project

K2NbO3F5 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are three inequivalent K sites. In the first K site, K is bonded in a 9-coordinate geometry to four O and five F atoms. There are a spread of K–O bond distances ranging from 2.91–3.04 Å. There are a spread of K–F bond distances ranging from 2.60–2.94 Å. In the second K site, K is bonded in a 10-coordinate geometry to ten F atoms. There are a spread of K–F bond distances ranging from 2.89–3.11 Å. In the third K site, K is bonded in a 10-coordinate geometry to ten F atoms. There are a spread of K–F bond distances ranging from 2.79–3.18 Å. Nb is bonded in a pentagonal bipyramidal geometry to two O and five F atoms. Both Nb–O bond lengths are 1.97 Å. There are a spread of Nb–F bond distances ranging from 1.99–2.06 Å. There are four inequivalent O sites. In the first O site, O is bonded in a 1-coordinate geometry to one K, one Nb, and one O atom. The O–O bond length is 1.47 Å. In the second O site, O is bonded in a 1-coordinate geometry to one K, one Nb, and one O atom. In the third O site, O is bonded in a distorted single-bond geometry to two equivalent K and one O atom. The O–O bond length is 1.25 Å. In the fourth O site, O is bonded in a distorted T-shaped geometry to two equivalent K and one O atom. There are five inequivalent F sites. In the first F site, F is bonded in a 4-coordinate geometry to three K and one Nb atom. In the second F site, F is bonded in a distorted single-bond geometry to three K and one Nb atom. In the third F site, F is bonded in a 4-coordinate geometry to three K and one Nb atom. In the fourth F site, F is bonded in a distorted single-bond geometry to three K and one Nb atom. In the fifth F site, F is bonded in a 4-coordinate geometry to three K and one Nb atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb2N3 by Materials Project

Nb2N3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Nb+4.50+ sites. In the first Nb+4.50+ site, Nb+4.50+ is bonded to seven N3- atoms to form a mixture of distorted edge and corner-sharing NbN7 pentagonal bipyramids. There are a spread of Nb–N bond distances ranging from 2.10–2.24 Å. In the second Nb+4.50+ site, Nb+4.50+ is bonded in a 8-coordinate geometry to eight N3- atoms. There are a spread of Nb–N bond distances ranging from 2.19–2.57 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded to five Nb+4.50+ atoms to form a mixture of distorted edge and corner-sharing NNb5 trigonal bipyramids. In the second N3- site, N3- is bonded to five Nb+4.50+ atoms to form a mixture of distorted edge and corner-sharing NNb5 trigonal bipyramids. In the third N3- site, N3- is bonded in a 4-coordinate geometry to five Nb+4.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb4WC5 by Materials Project

Nb4WC5 is Caswellsilverite-like structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Nb+4.50+ sites. In the first Nb+4.50+ site, Nb+4.50+ is bonded to six C4- atoms to form NbC6 octahedra that share corners with three equivalent NbC6 octahedra, corners with three equivalent WC6 octahedra, edges with three equivalent WC6 octahedra, and edges with nine NbC6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are three shorter (2.24 Å) and three longer (2.26 Å) Nb–C bond lengths. In the second Nb+4.50+ site, Nb+4.50+ is bonded to six C4- atoms to form a mixture of corner and edge-sharing NbC6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (2.24 Å) and three longer (2.25 Å) Nb–C bond lengths. W2+ is bonded to six equivalent C4- atoms to form WC6 octahedra that share corners with six equivalent NbC6 octahedra, edges with six equivalent NbC6 octahedra, and edges with six equivalent WC6 octahedra. The corner-sharing octahedral tilt angles are 2°. All W–C bond lengths are 2.20 Å. There are three inequivalent C4- sites. In the first C4- site, C4- is bonded to six Nb+4.50+ atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the second C4- site, C4- is bonded to six equivalent Nb+4.50+ atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the third C4- site, C4- is bonded to three equivalent Nb+4.50+ and three equivalent W2+ atoms to form a mixture of corner and edge-sharing CNb3W3 octahedra. The corner-sharing octahedra tilt angles range from 0–1°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb4Rh2C by Materials Project

Nb4Rh2C crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded in a 6-coordinate geometry to six equivalent Rh atoms. All Nb–Rh bond lengths are 2.63 Å. In the second Nb site, Nb is bonded in a 2-coordinate geometry to two equivalent Rh and two equivalent C atoms. Both Nb–Rh bond lengths are 2.77 Å. Both Nb–C bond lengths are 2.23 Å. Rh is bonded in a 12-coordinate geometry to six Nb atoms. C is bonded to six equivalent Nb atoms to form corner-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles are 36°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb5Ge3B by Materials Project

Nb5BGe3 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded in a 6-coordinate geometry to six equivalent Ge atoms. All Nb–Ge bond lengths are 2.73 Å. In the second Nb site, Nb is bonded in a 7-coordinate geometry to two equivalent B and five equivalent Ge atoms. Both Nb–B bond lengths are 2.32 Å. There are a spread of Nb–Ge bond distances ranging from 2.72–2.95 Å. B is bonded to six equivalent Nb atoms to form face-sharing BNb6 octahedra. Ge is bonded in a 9-coordinate geometry to nine Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb5(NO)2 by Materials Project

Nb5(NO)2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are five inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded to two N3- and three O2- atoms to form NbN2O3 square pyramids that share corners with six NbN2O3 square pyramids and edges with seven NbN3O2 square pyramids. There are one shorter (2.21 Å) and one longer (2.32 Å) Nb–N bond lengths. There are two shorter (2.23 Å) and one longer (2.41 Å) Nb–O bond lengths. In the second Nb2+ site, Nb2+ is bonded in a distorted rectangular see-saw-like geometry to two N3- and two O2- atoms. There are one shorter (2.13 Å) and one longer (2.21 Å) Nb–N bond lengths. There are one shorter (2.30 Å) and one longer (2.72 Å) Nb–O bond lengths. In the third Nb2+ site, Nb2+ is bonded to three N3- and two O2- atoms to form NbN3O2 square pyramids that share corners with six NbN3O2 square pyramids and edges with seven NbN2O3 square pyramids. There are two shorter (2.21 Å) and one longer (2.25 Å) Nb–N bond lengths. There are one shorter (2.24 Å) and one longer (2.26 Å) Nb–O bond lengths. In the fourth Nb2+ site, Nb2+ is bonded to three N3- and two O2- atoms to form a mixture of edge and corner-sharing NbN3O2 square pyramids. All Nb–N bond lengths are 2.22 Å. There are one shorter (2.33 Å) and one longer (2.35 Å) Nb–O bond lengths. In the fifth Nb2+ site, Nb2+ is bonded to two N3- and three O2- atoms to form a mixture of distorted edge and corner-sharing NbN2O3 square pyramids. There are one shorter (2.18 Å) and one longer (2.33 Å) Nb–N bond lengths. There are one shorter (2.22 Å) and two longer (2.23 Å) Nb–O bond lengths. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded to six Nb2+ atoms to form distorted NNb6 octahedra that share a cornercorner with one ONb6 octahedra, corners with three NNb6 octahedra, edges with three equivalent NNb6 octahedra, and edges with three equivalent ONb6 octahedra. The corner-sharing octahedra tilt angles range from 4–18°. In the second N3- site, N3- is bonded to six Nb2+ atoms to form NNb6 octahedra that share a cornercorner with one ONb6 octahedra, corners with three NNb6 octahedra, edges with three equivalent NNb6 octahedra, and edges with three equivalent ONb6 octahedra. The corner-sharing octahedra tilt angles range from 4–18°. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to six Nb2+ atoms to form ONb6 octahedra that share corners with two NNb6 octahedra, corners with two equivalent ONb6 octahedra, and edges with six NNb6 octahedra. The corner-sharing octahedra tilt angles range from 10–22°. In the second O2- site, O2- is bonded in a 5-coordinate geometry to six Nb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb2PbO6 by Materials Project

PbNb2O6 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are ten inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 14–20°. There are a spread of Nb–O bond distances ranging from 1.84–2.42 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 16–39°. There are a spread of Nb–O bond distances ranging from 1.85–2.38 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 15–28°. There are a spread of Nb–O bond distances ranging from 1.84–2.28 Å. In the fourth Nb5+ site, Nb5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.82–2.39 Å. In the fifth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 1–46°. There are a spread of Nb–O bond distances ranging from 1.86–2.33 Å. In the sixth Nb5+ site, Nb5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.84–2.50 Å. In the seventh Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 9–38°. There are a spread of Nb–O bond distances ranging from 1.92–2.16 Å. In the eighth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 1–38°. There are a spread of Nb–O bond distances ranging from 1.80–2.36 Å. In the ninth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 16–38°. There are a spread of Nb–O bond distances ranging from 1.88–2.25 Å. In the tenth Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 14–46°. There are a spread of Nb–O bond distances ranging from 1.88–2.19 Å. There are five inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 9-coordinate geometry to eight O2- atoms. There are a spread of Pb–O bond distances ranging from 2.49–3.02 Å. In the second Pb2+ site, Pb2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Pb–O bond distances ranging from 2.58–2.87 Å. In the third Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to three O2- atoms. There are one shorter (2.40 Å) and two longer (2.44 Å) Pb–O bond lengths. In the fourth Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Pb–O bond distances ranging from 2.39–2.98 Å. In the fifth Pb2+ site, Pb2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Pb–O bond distances ranging from 2.45–3.25 Å. There are thirty inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to two equivalent Nb5+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Nb5+ and one Pb2+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Nb5+ and one Pb2+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Nb5+ and two Pb2+ atoms. In the sixth O2- site, O2- is bonded in a distorted linear geometry to two Nb5+ atoms. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to two Nb5+ and two equivalent Pb2+ atoms. In the eighth O2- site, O2- is bonded in a linear geometry to two Nb5+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to two Nb5+ and two equivalent Pb2+ atoms. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to two Nb5+ and two equivalent Pb2+ atoms. In the eleventh O2- site, O2- is bonded in a 2-coordinate geometry to two Nb5+ and two equivalent Pb2+ atoms. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Nb5+ and one Pb2+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Nb5+ and two Pb2+ atoms. In the fourteenth O2- site, O2- is bonded in a linear geometry to two equivalent Nb5+ atoms. In the fifteenth O2- site, O2- is bonded in a linear geometry to two Nb5+ atoms. In the sixteenth O2- site, O2- is bonded in a linear geometry to two Nb5+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Nb5+ atoms. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Nb5+ and two equivalent Pb2+ atoms. In the twentieth O2- site, O2- is bonded in a 2-coordinate geometry to two Nb5+ and four Pb2+ atoms. In the twenty-first O2- site, O2- is bonded in a 2-coordinate geometry to two Nb5+ and two equivalent Pb2+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted single-bond geometry to two Nb5+ and two equivalent Pb2+ atoms. In the twenty-third O2- site, O2- is bonded to two Nb5+ and two equivalent Pb2+ atoms to form distorted corner-sharing ONb2Pb2 tetrahedra. In the twenty-fourth O2- site, O2- is bonded in a distorted single-bond geometry to two Nb5+ and two equivalent Pb2+ atoms. In the twenty-fifth O2- site, O2- is bonded in a 1-coordinate geometry to two Nb5+ and two equivalent Pb2+ atoms. In the twenty-sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Nb5+ and one Pb2+ atom. In the twenty-seventh O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Nb5+ and two Pb2+ atoms. In the twenty-eighth O2- site, O2- is bonded in a 4-coordinate geometry to two Nb5+ and two equivalent Pb2+ atoms. In the twenty-ninth O2- site, O2- is bonded in a 2-coordinate geometry to two Nb5+ atoms. In the thirtieth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Nb5+ and one Pb2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3NbHO2F7 by Materials Project

Na3NbHO2F7 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. there are three inequivalent Na sites. In the first Na site, Na is bonded to one O and six F atoms to form distorted NaOF6 pentagonal bipyramids that share a cornercorner with one NaOF5 octahedra, corners with three equivalent NbO2F5 pentagonal bipyramids, an edgeedge with one NaOF5 octahedra, an edgeedge with one NaOF6 pentagonal bipyramid, and an edgeedge with one NbO2F5 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 69°. The Na–O bond length is 2.44 Å. There are a spread of Na–F bond distances ranging from 2.30–2.61 Å. In the second Na site, Na is bonded in a 7-coordinate geometry to one O and six F atoms. The Na–O bond length is 2.62 Å. There are a spread of Na–F bond distances ranging from 2.37–2.76 Å. In the third Na site, Na is bonded to one O and five F atoms to form NaOF5 octahedra that share a cornercorner with one NaOF6 pentagonal bipyramid, corners with four equivalent NbO2F5 pentagonal bipyramids, and an edgeedge with one NaOF6 pentagonal bipyramid. The Na–O bond length is 2.46 Å. There are a spread of Na–F bond distances ranging from 2.30–2.41 Å. Nb is bonded to two O and five F atoms to form NbO2F5 pentagonal bipyramids that share corners with four equivalent NaOF5 octahedra, corners with three equivalent NaOF6 pentagonal bipyramids, and an edgeedge with one NaOF6 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 21–63°. There is one shorter (1.97 Å) and one longer (1.98 Å) Nb–O bond length. There are a spread of Nb–F bond distances ranging from 1.96–2.06 Å. There are two inequivalent H sites. In the first H site, H is bonded in a linear geometry to two equivalent F atoms. Both H–F bond lengths are 1.15 Å. In the second H site, H is bonded in a linear geometry to two equivalent F atoms. Both H–F bond lengths are 1.16 Å. There are two inequivalent O sites. In the first O site, O is bonded in a 4-coordinate geometry to two Na, one Nb, and one O atom. The O–O bond length is 1.47 Å. In the second O site, O is bonded in a 3-coordinate geometry to one Na, one Nb, and one O atom. There are seven inequivalent F sites. In the first F site, F is bonded in a distorted trigonal planar geometry to two Na and one Nb atom. In the second F site, F is bonded in a distorted single-bond geometry to three Na and one H atom. In the third F site, F is bonded in a bent 150 degrees geometry to one Na and one Nb atom. In the fourth F site, F is bonded in a distorted single-bond geometry to three Na and one H atom. In the fifth F site, F is bonded in a 3-coordinate geometry to two Na and one Nb atom. In the sixth F site, F is bonded in a 4-coordinate geometry to three Na and one Nb atom. In the seventh F site, F is bonded in a distorted tetrahedral geometry to three Na and one Nb atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Phase Discovery and Selected Synthesis of Subvalent Niobium Tellurides Using a Polytelluride Flux Strategy

Transition metal subchalcogenides involve electron-rich metals and can facilitate an in-depth understanding of the relationships among quantum properties such as superconductivity, charge density wave, and topological band structures. However, effective experimental routes toward synthesizing transition metal subchalcogenides are still lacking, hindering the development of new quantum materials. Herein, we propose a eutectic polytelluride flux strategy as an excellent solution to address phase discovery and crystal growth in transition metal subtelluride systems. We report new phases easily and selectively synthesized using a eutectic “K 3 Te 4 ” polytelluride flux upon adjusting the ratio of Nb metal to flux in the starting materials (K/Nb/Te = 3:x:4). Using a high Nb content in the solvent (x = 2 and 1), crystals of KNb 3 Te 3 O 0.38 and K 0.9 Nb 3 Te 4 are obtained. Both subtellurides exhibit diverse Nb clusters, including face-sharing and edge-sharing Nb 6 octahedral columns and zig-zag Nb chains. Reducing the Nb content to x = 0.33 leads to the formation of a layered compound, K 1.06 NbTe 2 . This compound comprises a NbTe 6 trigonal prism with K intercalated between the layers. Single crystals of known binary Nb tellurides can also be grown using another eutectic flux “KTe 3 . 2 ”, and the obtained NbTe 2 exhibits a new polymorphism with extra trimerization along the b-axis in the Nb–Nb bonded double zig-zag cluster. Finally, precise control over the structural dimensionality and oxidation state, combined with the facile crystal growth process, makes our synthetic strategy an efficient route to explore quantum materials in transition metal subchalcogenides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Development and characterization of Nb3Sn/Al2O3 superconducting multilayers for particle accelerators

Abstract Superconducting radio-frequency (SRF) resonator cavities provide extremely high quality factors > 10 10 at 1–2 GHz and 2 K in large linear accelerators of high-energy particles. The maximum accelerating field of SRF cavities is limited by penetration of vortices into the superconductor. Present state-of-the-art Nb cavities can withstand up to 50 MV/m accelerating gradients and magnetic fields of 200–240 mT which destroy the low-dissipative Meissner state. Achieving higher accelerating gradients requires superconductors with higher thermodynamic critical fields, of which Nb 3 Sn has emerged as a leading material for the next generation accelerators. To overcome the problem of low vortex penetration field in Nb 3 Sn, it has been proposed to coat Nb cavities with thin film Nb 3 Sn multilayers with dielectric interlayers. Here, we report the growth and multi-technique characterization of stoichiometric Nb 3 Sn/Al 2 O 3 multilayers with good superconducting and RF properties. We developed an adsorption-controlled growth process by co-sputtering Nb and Sn at high temperatures with a high overpressure of Sn. The cross-sectional scanning electron transmission microscope images show no interdiffusion between Al 2 O 3 and Nb 3 Sn. Low-field RF measurements suggest that our multilayers have quality factor comparable with cavity-grade Nb at 4.2 K. These results provide a materials platform for the development and optimization of high-performance SIS multilayers which could overcome the intrinsic limits of the Nb cavity technology.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Cylindrical Magnetron Development for Nb3sn Deposition via Magnetron Sputtering

Due to its better superconducting properties (critical temperature Tc~ 18.3 K, superheating field Hsh~ 400 mT), Nb₃Sn is considered as a potential alternative to niobium (Tc~ 9.25 K, Hsh~ 200 mT) for superconducting radiofrequency (SRF) cavities for particle acceleration. Magnetron sputtering is an effective method to produce superconducting Nb₃Sn films. We deposited superconducting Nb₃Sn films on samples with magnetron sputtering using co-sputtering, sequential sputtering, and sputtering from a stoichiometric target. Nb₃Sn films produced by magnetron sputtering in our previous experiments have achieved DC superconducting critical temperature up to 17.93 K and RF superconducting transition at 17.2 K. A magnetron sputtering system with two identical cylindrical cathodes that can be used to sputter Nb₃Sn films on cavities has been designed and is under development now. We report on the design and the current progress on the development of the system.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Materials Data on Nb5Si3 by Materials Project

Nb5Si3 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. there are two inequivalent Nb+2.40+ sites. In the first Nb+2.40+ site, Nb+2.40+ is bonded to six Si4- atoms to form NbSi6 octahedra that share corners with six equivalent NbSi6 octahedra, corners with sixteen equivalent NbSi5 trigonal bipyramids, and faces with eight equivalent NbSi5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 0–52°. There are four shorter (2.60 Å) and two longer (2.99 Å) Nb–Si bond lengths. In the second Nb+2.40+ site, Nb+2.40+ is bonded to five Si4- atoms to form NbSi5 trigonal bipyramids that share corners with four equivalent NbSi6 octahedra, corners with twelve equivalent NbSi5 trigonal bipyramids, edges with seven equivalent NbSi5 trigonal bipyramids, faces with two equivalent NbSi6 octahedra, and a faceface with one NbSi5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 43–64°. There are a spread of Nb–Si bond distances ranging from 2.61–2.74 Å. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 10-coordinate geometry to ten Nb+2.40+ atoms. In the second Si4- site, Si4- is bonded in a 9-coordinate geometry to eight Nb+2.40+ and one Si4- atom. The Si–Si bond length is 2.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb4CrSe8 by Materials Project

Nb4CrSe8 crystallizes in the hexagonal P6_3/mmc 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 six equivalent Se2- atoms to form NbSe6 octahedra that share edges with six equivalent NbSe6 octahedra and faces with two equivalent CrSe6 pentagonal pyramids. All Nb–Se bond lengths are 2.65 Å. In the second Nb+3.50+ site, Nb+3.50+ is bonded to six Se2- atoms to form NbSe6 octahedra that share corners with four equivalent CrSe6 pentagonal pyramids and edges with six NbSe6 octahedra. There are two shorter (2.62 Å) and four longer (2.64 Å) Nb–Se bond lengths. Cr2+ is bonded to six equivalent Se2- atoms to form distorted CrSe6 pentagonal pyramids that share corners with twelve equivalent NbSe6 octahedra and faces with two equivalent NbSe6 octahedra. The corner-sharing octahedral tilt angles are 45°. All Cr–Se bond lengths are 2.68 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Nb+3.50+ and one Cr2+ atom to form a mixture of distorted corner and edge-sharing SeNb3Cr trigonal pyramids. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3(Fe10B3)2 by Materials Project

Nb3(Fe10B3)2 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 in a distorted tetrahedral geometry to four equivalent Fe atoms. All Nb–Fe bond lengths are 2.50 Å. In the second Nb site, Nb is bonded in a distorted cuboctahedral geometry to twelve equivalent Fe atoms. All Nb–Fe bond lengths are 2.63 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted bent 150 degrees geometry to one Nb and two equivalent B atoms. Both Fe–B bond lengths are 2.13 Å. In the second Fe site, Fe is bonded to one Nb and three equivalent B atoms to form a mixture of distorted edge and corner-sharing FeNbB3 tetrahedra. All Fe–B bond lengths are 2.13 Å. B is bonded in a 8-coordinate geometry to eight Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Be17Nb2 by Materials Project

Be17Nb2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are four inequivalent Be sites. In the first Be site, Be is bonded in a 1-coordinate geometry to thirteen Be and one Nb atom. There are a spread of Be–Be bond distances ranging from 2.12–2.41 Å. The Be–Nb bond length is 2.60 Å. In the second Be site, Be is bonded in a 12-coordinate geometry to ten Be and two equivalent Nb atoms. There are four shorter (2.11 Å) and four longer (2.15 Å) Be–Be bond lengths. Both Be–Nb bond lengths are 2.84 Å. In the third Be site, Be is bonded to ten Be and two equivalent Nb atoms to form distorted BeBe10Nb2 cuboctahedra that share corners with twenty BeBe9Nb3 cuboctahedra, edges with three BeBe9Nb3 cuboctahedra, and faces with seventeen BeBe10Nb2 cuboctahedra. There are a spread of Be–Be bond distances ranging from 2.17–2.26 Å. Both Be–Nb bond lengths are 2.62 Å. In the fourth Be site, Be is bonded to nine Be and three equivalent Nb atoms to form distorted BeBe9Nb3 cuboctahedra that share corners with eighteen BeBe9Nb3 cuboctahedra, edges with seven BeBe9Nb3 cuboctahedra, and faces with seventeen BeBe10Nb2 cuboctahedra. Both Be–Be bond lengths are 2.11 Å. There are one shorter (2.63 Å) and two longer (2.78 Å) Be–Nb bond lengths. Nb is bonded in a 10-coordinate geometry to nineteen Be atoms.

36 MATERIALS SCIENCE↗