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Experiments to Measure the Effect of Tantalum on Critical Systems

Sandia National Laboratories (SNL) and Oak Ridge National Laboratory (ORNL) collaborated to develop a capability to test the epithermal/intermediate cross sections of materials at the SNL critical experiment facility using the Seven Percent Critical Experiment (7uPCX) fuel. As a result, a new set of critical experiments has been designed to target the epithermal cross sections of tantalum (Ta) and is scheduled to be performed at SNL in 2023. These critical experiments will be evaluated for inclusion in the 2024 edition of the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook. The focus of these critical experiments is to measure the effects of Ta on the critical array size. The critical array size will be determined by an approach-to-critical experiment with the number of fuel rods in the array as a free parameter. The core configurations are designed to optimize the reactivity worth of Ta and the overall percentage of Ta absorption rates in the epithermal/intermediate energy range (0.625 eV – 100 keV). The baseline core configuration includes 7uPCX fuel rods set at a triangular pitch of 1.016 cm and a central dry test region that utilizes a cadmium liner for filtering out thermal neutrons. The central test region has locations for 85 Ta rods set at a triangular pitch of 0.813 cm. The Ta reactivity worth for the case with 85 Ta rods is approximately 2.55%, with the percentage of Ta absorption rates within the intermediate energy range at nearly 90%.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Materials Data on TaBe12 by Materials Project

Be12Ta crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are three inequivalent Be sites. In the first Be site, Be is bonded in a 10-coordinate geometry to nine Be and one Ta atom. There are a spread of Be–Be bond distances ranging from 2.15–2.34 Å. The Be–Ta bond length is 2.57 Å. In the second Be site, Be is bonded to ten Be and two equivalent Ta atoms to form a mixture of distorted corner, edge, and face-sharing BeTa2Be10 cuboctahedra. There are two shorter (2.11 Å) and four longer (2.12 Å) Be–Be bond lengths. Both Be–Ta bond lengths are 2.79 Å. In the third Be site, Be is bonded in a distorted q6 geometry to ten Be and two equivalent Ta atoms. Both Be–Be bond lengths are 2.23 Å. Both Be–Ta bond lengths are 2.63 Å. Ta is bonded in a 12-coordinate geometry to twenty Be atoms.

36 MATERIALS SCIENCE↗

Materials Data on TaMn2 by Materials Project

TaMn2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Mn atoms. All Ta–Ta bond lengths are 2.95 Å. All Ta–Mn bond lengths are 2.82 Å. There are two inequivalent Mn sites. In the first Mn site, Mn is bonded to six equivalent Ta and six equivalent Mn atoms to form a mixture of corner, edge, and face-sharing MnTa6Mn6 cuboctahedra. All Mn–Mn bond lengths are 2.44 Å. In the second Mn site, Mn is bonded to six equivalent Ta and six Mn atoms to form a mixture of corner, edge, and face-sharing MnTa6Mn6 cuboctahedra. There are two shorter (2.33 Å) and two longer (2.48 Å) Mn–Mn bond lengths.

36 MATERIALS SCIENCE↗

Materials Data on Ta3Al2CoC by Materials Project

Ta3Al2CoC crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ta is bonded in a distorted bent 150 degrees geometry to two equivalent Co, four equivalent Al, and two equivalent C atoms. Both Ta–Co bond lengths are 2.98 Å. There are two shorter (2.77 Å) and two longer (2.98 Å) Ta–Al bond lengths. Both Ta–C bond lengths are 2.18 Å. Co is bonded to six equivalent Ta and six equivalent Al atoms to form CoTa6Al6 cuboctahedra that share edges with six equivalent CTa6 octahedra and faces with six equivalent CoTa6Al6 cuboctahedra. All Co–Al bond lengths are 2.50 Å. Al is bonded in a 12-coordinate geometry to six equivalent Ta, three equivalent Co, and three equivalent Al atoms. All Al–Al bond lengths are 2.69 Å. C is bonded to six equivalent Ta atoms to form CTa6 octahedra that share corners with six equivalent CTa6 octahedra and edges with six equivalent CoTa6Al6 cuboctahedra. The corner-sharing octahedral tilt angles are 40°.

36 MATERIALS SCIENCE↗

Materials Data on TaSe2 by Materials Project

TaSe2 is trigonal omega-like structured and crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one TaSe2 sheet oriented in the (1, 1, 1) direction. there are seven inequivalent Ta4+ sites. In the first Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. All Ta–Se bond lengths are 2.66 Å. In the second Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.56–2.73 Å. In the third Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.56–2.73 Å. In the fourth Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.56–2.73 Å. In the fifth Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.48–2.77 Å. In the sixth Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.48–2.76 Å. In the seventh Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.48–2.76 Å. There are thirteen inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the third Se2- site, Se2- is bonded in a distorted T-shaped geometry to three Ta4+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the fifth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the sixth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the seventh Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the eighth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the ninth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the tenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the eleventh Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the twelfth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the thirteenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on TaSn2 by Materials Project

TaSn2 is Khatyrkite-like structured and crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Ta is bonded in a 10-coordinate geometry to two equivalent Ta and eight Sn atoms. Both Ta–Ta bond lengths are 2.86 Å. There are a spread of Ta–Sn bond distances ranging from 2.89–2.99 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Ta atoms. In the second Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Ta atoms.

36 MATERIALS SCIENCE↗

Materials Data on TaFe2 by Materials Project

TaFe2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Fe atoms. There are one shorter (2.91 Å) and three longer (2.95 Å) Ta–Ta bond lengths. There are a spread of Ta–Fe bond distances ranging from 2.80–2.84 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six equivalent Ta and six equivalent Fe atoms to form a mixture of edge, face, and corner-sharing FeTa6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.42 Å. In the second Fe site, Fe is bonded to six equivalent Ta and six Fe atoms to form a mixture of edge, face, and corner-sharing FeTa6Fe6 cuboctahedra. There are two shorter (2.37 Å) and two longer (2.41 Å) Fe–Fe bond lengths.

36 MATERIALS SCIENCE↗

Materials Data on TaCo2 by Materials Project

Co2Ta is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Co atoms. There are one shorter (2.87 Å) and three longer (2.93 Å) Ta–Ta bond lengths. There are a spread of Ta–Co bond distances ranging from 2.78–2.80 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Ta and six equivalent Co atoms to form a mixture of corner, edge, and face-sharing CoTa6Co6 cuboctahedra. All Co–Co bond lengths are 2.38 Å. In the second Co site, Co is bonded to six equivalent Ta and six Co atoms to form a mixture of corner, edge, and face-sharing CoTa6Co6 cuboctahedra. There are two shorter (2.36 Å) and two longer (2.41 Å) Co–Co bond lengths.

36 MATERIALS SCIENCE↗

Materials Data on TaCr2 by Materials Project

Cr2Ta is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Cr atoms. There are three shorter (2.99 Å) and one longer (3.04 Å) Ta–Ta bond lengths. There are a spread of Ta–Cr bond distances ranging from 2.86–2.88 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to six equivalent Ta and six equivalent Cr atoms to form a mixture of face, edge, and corner-sharing CrTa6Cr6 cuboctahedra. All Cr–Cr bond lengths are 2.47 Å. In the second Cr site, Cr is bonded to six equivalent Ta and six Cr atoms to form a mixture of face, edge, and corner-sharing CrTa6Cr6 cuboctahedra. There are two shorter (2.41 Å) and two longer (2.50 Å) Cr–Cr bond lengths.

36 MATERIALS SCIENCE↗

Materials Data on Cs2LaTa6(Br5O)3 by Materials Project

Cs2LaTa6Br15O3 crystallizes in the trigonal P-31c space group. The structure is three-dimensional. Cs is bonded in a 9-coordinate geometry to nine Br atoms. There are a spread of Cs–Br bond distances ranging from 3.76–3.93 Å. La is bonded in a distorted trigonal planar geometry to three equivalent O and six equivalent Br atoms. All La–O bond lengths are 2.57 Å. All La–Br bond lengths are 3.31 Å. Ta is bonded in a 1-coordinate geometry to one O and four Br atoms. The Ta–O bond length is 1.99 Å. There are a spread of Ta–Br bond distances ranging from 2.61–2.78 Å. O is bonded in a 3-coordinate geometry to one La and two equivalent Ta atoms. There are three inequivalent Br sites. In the first Br site, Br is bonded in a 4-coordinate geometry to two equivalent Cs, one La, and one Ta atom. In the second Br site, Br is bonded in a 3-coordinate geometry to one Cs and two equivalent Ta atoms. In the third Br site, Br is bonded in a 2-coordinate geometry to two equivalent Ta atoms.

36 MATERIALS SCIENCE↗

Materials Data on Na2LiTa by Materials Project

Na2LiTa crystallizes in the cubic F-43m space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded to four equivalent Na and four equivalent Ta atoms to form distorted edge-sharing NaNa4Ta4 tetrahedra. All Na–Na bond lengths are 3.10 Å. All Na–Ta bond lengths are 3.10 Å. In the second Na site, Na is bonded in a 8-coordinate geometry to four equivalent Na, four equivalent Li, and six equivalent Ta atoms. All Na–Li bond lengths are 3.10 Å. All Na–Ta bond lengths are 3.58 Å. Li is bonded in a distorted body-centered cubic geometry to four equivalent Na and four equivalent Ta atoms. All Li–Ta bond lengths are 3.10 Å. Ta is bonded in a distorted body-centered cubic geometry to ten Na and four equivalent Li atoms.

36 MATERIALS SCIENCE↗

Materials Data on Cs2UTa6(Cl5O)3 by Materials Project

Cs2UTa6(OCl5)3 crystallizes in the trigonal P-31c space group. The structure is three-dimensional. Cs is bonded in a 12-coordinate geometry to twelve Cl atoms. There are a spread of Cs–Cl bond distances ranging from 3.52–4.02 Å. U is bonded in a trigonal planar geometry to three equivalent O and six equivalent Cl atoms. All U–O bond lengths are 2.33 Å. All U–Cl bond lengths are 3.18 Å. Ta is bonded in a 5-coordinate geometry to one O and four Cl atoms. The Ta–O bond length is 2.03 Å. There are a spread of Ta–Cl bond distances ranging from 2.48–2.61 Å. O is bonded in a distorted T-shaped geometry to one U and two equivalent Ta atoms. There are three inequivalent Cl sites. In the first Cl site, Cl is bonded in a 4-coordinate geometry to two equivalent Cs, one U, and one Ta atom. In the second Cl site, Cl is bonded in a 3-coordinate geometry to one Cs and two equivalent Ta atoms. In the third Cl site, Cl is bonded in a 2-coordinate geometry to two equivalent Cs and two equivalent Ta atoms.

36 MATERIALS SCIENCE↗

Materials Data on LaTa2NO5 by Materials Project

LaTa2NO5 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of La–O bond distances ranging from 2.44–2.67 Å. In the second La3+ site, La3+ is bonded in a 8-coordinate geometry to two N3- and six O2- atoms. There are one shorter (2.51 Å) and one longer (2.58 Å) La–N bond lengths. There are a spread of La–O bond distances ranging from 2.53–2.65 Å. There are four inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to one N3- and five O2- atoms to form distorted TaNO5 octahedra that share corners with four TaO6 octahedra and an edgeedge with one TaNO5 octahedra. The corner-sharing octahedra tilt angles range from 27–48°. The Ta–N bond length is 1.88 Å. There are a spread of Ta–O bond distances ranging from 2.02–2.31 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaNO5 octahedra and an edgeedge with one TaN2O4 octahedra. The corner-sharing octahedra tilt angles range from 27–47°. There are a spread of Ta–O bond distances ranging from 1.94–2.11 Å. In the third Ta5+ site, Ta5+ is bonded to two N3- and four O2- atoms to form TaN2O4 octahedra that share corners with four TaNO5 octahedra and an edgeedge with one TaO6 octahedra. The corner-sharing octahedra tilt angles range from 29–48°. There is one shorter (1.98 Å) and one longer (1.99 Å) Ta–N bond length. There are a spread of Ta–O bond distances ranging from 1.96–2.21 Å. In the fourth Ta5+ site, Ta5+ is bonded to one N3- and five O2- atoms to form TaNO5 octahedra that share corners with four TaO6 octahedra and an edgeedge with one TaNO5 octahedra. The corner-sharing octahedra tilt angles range from 29–47°. The Ta–N bond length is 1.95 Å. There are a spread of Ta–O bond distances ranging from 1.97–2.16 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a 3-coordinate geometry to one La3+ and two Ta5+ atoms. In the second N3- site, N3- is bonded in a 2-coordinate geometry to one La3+ and two Ta5+ atoms. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded to two La3+ and two Ta5+ atoms to form distorted corner-sharing OLa2Ta2 tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two La3+ and two Ta5+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one La3+ and two Ta5+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one La3+ and two Ta5+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one La3+ and two Ta5+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one La3+ and two Ta5+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one La3+ and two Ta5+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one La3+ and two Ta5+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two La3+ and two Ta5+ atoms. In the tenth O2- site, O2- is bonded to two La3+ and two Ta5+ atoms to form distorted corner-sharing OLa2Ta2 tetrahedra.

36 MATERIALS SCIENCE↗

Materials Data on TaTiNi6 by Materials Project

TiTaNi6 is beta Cu3Ti-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ti is bonded to twelve Ni atoms to form TiNi12 cuboctahedra that share corners with six equivalent TiNi12 cuboctahedra, corners with twelve NiTa2Ti2Ni8 cuboctahedra, edges with eighteen NiTa2Ti2Ni8 cuboctahedra, faces with two equivalent TiNi12 cuboctahedra, faces with six equivalent TaNi12 cuboctahedra, and faces with twelve NiTa2Ti2Ni8 cuboctahedra. There are six shorter (2.56 Å) and six longer (2.60 Å) Ti–Ni bond lengths. Ta is bonded to twelve Ni atoms to form TaNi12 cuboctahedra that share corners with six equivalent TaNi12 cuboctahedra, corners with twelve NiTa2Ti2Ni8 cuboctahedra, edges with eighteen NiTa2Ti2Ni8 cuboctahedra, faces with two equivalent TaNi12 cuboctahedra, faces with six equivalent TiNi12 cuboctahedra, and faces with twelve NiTa2Ti2Ni8 cuboctahedra. There are six shorter (2.56 Å) and six longer (2.60 Å) Ta–Ni bond lengths. There are five inequivalent Ni sites. In the first Ni site, Ni is bonded to two equivalent Ti, two equivalent Ta, and eight Ni atoms to form distorted NiTa2Ti2Ni8 cuboctahedra that share corners with four equivalent TaNi12 cuboctahedra, corners with fourteen NiTa2Ti2Ni8 cuboctahedra, edges with two equivalent TaNi12 cuboctahedra, edges with four equivalent TiNi12 cuboctahedra, edges with twelve NiTa2Ti2Ni8 cuboctahedra, faces with two equivalent TiNi12 cuboctahedra, faces with two equivalent TaNi12 cuboctahedra, and faces with sixteen NiTa2Ti2Ni8 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.52–2.61 Å. In the second Ni site, Ni is bonded to two equivalent Ti, two equivalent Ta, and eight Ni atoms to form distorted NiTa2Ti2Ni8 cuboctahedra that share corners with four equivalent TaNi12 cuboctahedra, corners with fourteen NiTa2Ti2Ni8 cuboctahedra, edges with two equivalent TaNi12 cuboctahedra, edges with four equivalent TiNi12 cuboctahedra, edges with twelve NiTa2Ti2Ni8 cuboctahedra, faces with two equivalent TiNi12 cuboctahedra, faces with two equivalent TaNi12 cuboctahedra, and faces with sixteen NiTa2Ti2Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.56 Å. In the third Ni site, Ni is bonded to two equivalent Ti, two equivalent Ta, and eight Ni atoms to form distorted NiTa2Ti2Ni8 cuboctahedra that share corners with four equivalent TiNi12 cuboctahedra, corners with fourteen NiTa2Ti2Ni8 cuboctahedra, edges with two equivalent TiNi12 cuboctahedra, edges with four equivalent TaNi12 cuboctahedra, edges with twelve NiTa2Ti2Ni8 cuboctahedra, faces with two equivalent TiNi12 cuboctahedra, faces with two equivalent TaNi12 cuboctahedra, and faces with sixteen NiTa2Ti2Ni8 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.49–2.63 Å. In the fourth Ni site, Ni is bonded to two equivalent Ti, two equivalent Ta, and eight Ni atoms to form distorted NiTa2Ti2Ni8 cuboctahedra that share corners with four equivalent TiNi12 cuboctahedra, corners with fourteen NiTa2Ti2Ni8 cuboctahedra, edges with two equivalent TiNi12 cuboctahedra, edges with four equivalent TaNi12 cuboctahedra, edges with twelve NiTa2Ti2Ni8 cuboctahedra, faces with two equivalent TiNi12 cuboctahedra, faces with two equivalent TaNi12 cuboctahedra, and faces with sixteen NiTa2Ti2Ni8 cuboctahedra. There are one shorter (2.49 Å) and one longer (2.63 Å) Ni–Ni bond lengths. In the fifth Ni site, Ni is bonded to two equivalent Ti, two equivalent Ta, and eight Ni atoms to form distorted NiTa2Ti2Ni8 cuboctahedra that share corners with four equivalent TiNi12 cuboctahedra, corners with fourteen NiTa2Ti2Ni8 cuboctahedra, edges with two equivalent TiNi12 cuboctahedra, edges with four equivalent TaNi12 cuboctahedra, edges with twelve NiTa2Ti2Ni8 cuboctahedra, faces with two equivalent TiNi12 cuboctahedra, faces with two equivalent TaNi12 cuboctahedra, and faces with sixteen NiTa2Ti2Ni8 cuboctahedra.

36 MATERIALS SCIENCE↗

Materials Data on Ta2In(ReSe4)2 by Materials Project

TaSe2TaInSe2(ReSe2)2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of two ReSe2 sheets oriented in the (0, 0, 1) direction; one TaInSe2 sheet oriented in the (0, 0, 1) direction; and one TaSe2 sheet oriented in the (0, 0, 1) direction. In each ReSe2 sheet, Re3+ is bonded to six Se2- atoms to form distorted edge-sharing ReSe6 pentagonal pyramids. There are three shorter (2.53 Å) and three longer (2.54 Å) Re–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Re3+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Re3+ atoms. In the TaInSe2 sheet, Ta+4.50+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. There are three shorter (2.61 Å) and three longer (2.62 Å) Ta–Se bond lengths. In1+ is bonded in a 6-coordinate geometry to three equivalent Se2- atoms. All In–Se bond lengths are 3.16 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta+4.50+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to three equivalent Ta+4.50+ and three equivalent In1+ atoms. In the TaSe2 sheet, Ta+4.50+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta+4.50+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on Sr3LaTaAl3O12 by Materials Project

Sr3LaTaAl3O12 is (Cubic) Perovskite-derived structured and crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are three inequivalent Sr sites. In the first Sr site, Sr is bonded to twelve O atoms to form SrO12 cuboctahedra that share corners with four equivalent LaO12 cuboctahedra, corners with eight SrO12 cuboctahedra, faces with six SrO12 cuboctahedra, faces with two equivalent TaO6 octahedra, and faces with six AlO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.65–2.93 Å. In the second Sr site, Sr is bonded to twelve O atoms to form SrO12 cuboctahedra that share corners with four equivalent LaO12 cuboctahedra, corners with eight SrO12 cuboctahedra, faces with two equivalent LaO12 cuboctahedra, faces with four SrO12 cuboctahedra, faces with two equivalent TaO6 octahedra, and faces with six AlO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.62–2.86 Å. In the third Sr site, Sr is bonded to twelve O atoms to form SrO12 cuboctahedra that share corners with four equivalent LaO12 cuboctahedra, corners with eight SrO12 cuboctahedra, faces with two equivalent LaO12 cuboctahedra, faces with four SrO12 cuboctahedra, faces with two equivalent TaO6 octahedra, and faces with six AlO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.62–2.86 Å. La is bonded to twelve O atoms to form LaO12 cuboctahedra that share corners with twelve SrO12 cuboctahedra, faces with two equivalent LaO12 cuboctahedra, faces with four SrO12 cuboctahedra, faces with two equivalent TaO6 octahedra, and faces with six AlO6 octahedra. There are a spread of La–O bond distances ranging from 2.53–2.89 Å. Ta is bonded to six O atoms to form TaO6 octahedra that share corners with two equivalent TaO6 octahedra, corners with four AlO6 octahedra, faces with two equivalent LaO12 cuboctahedra, and faces with six SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 2–3°. There is four shorter (1.96 Å) and two longer (1.99 Å) Ta–O bond length. There are three inequivalent Al sites. In the first Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with two equivalent TaO6 octahedra, corners with four AlO6 octahedra, faces with two equivalent LaO12 cuboctahedra, and faces with six SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 1–4°. There are a spread of Al–O bond distances ranging from 1.90–1.96 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with two equivalent TaO6 octahedra, corners with four AlO6 octahedra, faces with two equivalent LaO12 cuboctahedra, and faces with six SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 1–4°. There are a spread of Al–O bond distances ranging from 1.90–1.96 Å. In the third Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with six AlO6 octahedra, faces with two equivalent LaO12 cuboctahedra, and faces with six SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 1–5°. There is two shorter (1.91 Å) and four longer (1.96 Å) Al–O bond length. There are twelve inequivalent O sites. In the first O site, O is bonded in a distorted linear geometry to three Sr, one La, and two equivalent Al atoms. In the second O site, O is bonded in a distorted linear geometry to three Sr, one La, and two equivalent Ta atoms. In the third O site, O is bonded to three Sr, one La, and two equivalent Al atoms to form distorted OSr3LaAl2 octahedra that share corners with two equivalent OSr3LaAl2 octahedra and faces with eight OSr4Al2 octahedra. The corner-sharing octahedral tilt angles are 5°. In the fourth O site, O is bonded in a distorted linear geometry to three Sr, one La, and two equivalent Al atoms. In the fifth O site, O is bonded in a distorted linear geometry to four Sr, one Ta, and one Al atom. In the sixth O site, O is bonded to four Sr and two Al atoms to form distorted OSr4Al2 octahedra that share corners with six OSr2La2Al2 octahedra, edges with two equivalent OSr4Al2 octahedra, and faces with four OSr3LaAl2 octahedra. The corner-sharing octahedra tilt angles range from 2–56°. In the seventh O site, O is bonded in a distorted linear geometry to two equivalent Sr, two equivalent La, one Ta, and one Al atom. In the eighth O site, O is bonded to two equivalent Sr, two equivalent La, and two Al atoms to form distorted OSr2La2Al2 octahedra that share corners with six OSr4Al2 octahedra, edges with two equivalent OSr2La2Al2 octahedra, and faces with four OSr3LaAl2 octahedra. The corner-sharing octahedra tilt angles range from 2–56°. In the ninth O site, O is bonded in a distorted linear geometry to four Sr, one Ta, and one Al atom. In the tenth O site, O is bonded in a distorted linear geometry to two equivalent Sr, two equivalent La, one Ta, and one Al atom. In the eleventh O site, O is bonded to four Sr and two Al atoms to form distorted OSr4Al2 octahedra that share corners with six OSr4Al2 octahedra, edges with two equivalent OSr4Al2 octahedra, and faces with four OSr3LaAl2 octahedra. The corner-sharing octahedra tilt angles range from 2–56°. In the twelfth O site, O is bonded to two equivalent Sr, two equivalent La, and two Al atoms to form distorted OSr2La2Al2 octahedra that share corners with six OSr4Al2 octahedra, edges with two equivalent OSr2La2Al2 octahedra, and faces with four OSr3LaAl2 octahedra. The corner-sharing octahedra tilt angles range from 2–56°.

36 MATERIALS SCIENCE↗

Materials Data on Cs2CeTa6(Br5O)3 by Materials Project

Cs2CeTa6(OBr5)3 crystallizes in the trigonal P-31c space group. The structure is three-dimensional. Cs is bonded in a 12-coordinate geometry to twelve Br atoms. There are a spread of Cs–Br bond distances ranging from 3.72–4.25 Å. Ce is bonded in a distorted trigonal planar geometry to three equivalent O and six equivalent Br atoms. All Ce–O bond lengths are 2.56 Å. All Ce–Br bond lengths are 3.31 Å. Ta is bonded in a 1-coordinate geometry to one O and four Br atoms. The Ta–O bond length is 1.99 Å. There are a spread of Ta–Br bond distances ranging from 2.61–2.79 Å. O is bonded in a 3-coordinate geometry to one Ce and two equivalent Ta atoms. There are three inequivalent Br sites. In the first Br site, Br is bonded in a 4-coordinate geometry to two equivalent Cs, one Ce, and one Ta atom. In the second Br site, Br is bonded in a 2-coordinate geometry to two equivalent Cs and two equivalent Ta atoms. In the third Br site, Br is bonded in a 3-coordinate geometry to one Cs and two equivalent Ta atoms.

36 MATERIALS SCIENCE↗

Materials Data on Ta3Al4O14 by Materials Project

Ta3Al4O14 is Hydrophilite-derived structured and crystallizes in the trigonal P3 space group. The structure is three-dimensional. Ta is bonded to six O atoms to form TaO6 octahedra that share corners with eight AlO6 octahedra and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Ta–O bond distances ranging from 1.93–2.10 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with six equivalent TaO6 octahedra and edges with three AlO6 octahedra. The corner-sharing octahedra tilt angles range from 45–54°. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with six equivalent TaO6 octahedra and edges with three equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–55°. There is three shorter (1.90 Å) and three longer (1.91 Å) Al–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to one Ta and two Al atoms. In the second O site, O is bonded in a trigonal planar geometry to two equivalent Ta and one Al atom. In the third O site, O is bonded in a distorted trigonal planar geometry to one Ta and two Al atoms. In the fourth O site, O is bonded in a distorted trigonal planar geometry to one Ta and two equivalent Al atoms. In the fifth O site, O is bonded in a trigonal non-coplanar geometry to three equivalent Ta atoms. In the sixth O site, O is bonded in a trigonal non-coplanar geometry to three equivalent Al atoms.

36 MATERIALS SCIENCE↗