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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Synthesis, structure, and transport properties of Ba 8 Cu 16 – x Au x P 30 clathrate solid solution

In this work, a new clathrate solid solution Ba 8 Cu 16 – x Au x P 30 ( x = 4, 8, 12) was synthesized by a high-temperature solid-state annealing method. The crystal structures of Ba 8 Cu 16 – x Au x P 30 were determined by single crystal x-ray diffraction. This clathrate solid solution crystallizes in the orthorhombic superstructure of clathrate-I type with 23 crystallographically independent framework sites, eight of them are occupied by Au/Cu and 15 are exclusively occupied by P atoms. The distribution of Au and Cu atoms over these eight framework sites is not random with a clear preference for Au to occupy the largest (Au/Cu)P 4 tetrahedra in the framework. The thermal stability and thermoelectric properties of the Ba 8 Cu 16 – x Au x P 30 solid solution were evaluated. Low thermal conductivity was achieved for Ba 8 Cu 16 – x Au x P 30 due to the combination of the host–guest crystal structure with rattling Ba atoms with the presence of heavy Au atoms and substitutional Cu/Au disorder in the clathrate framework.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electronic structure and two-band superconductivity in unconventional high- T c cuprates Ba 2 CuO 3+δ

We report that the recently discovered cuprate superconductor Ba 2 CuO 3+δ exhibits a high T c ≃73 K at δ ≃ 0.2. The polycrystal grown under high pressure has a structure similar to La 2 CuO 4 but with dramatically different lattice parameters due to the CuO 6 octahedron compression. The crystal field in the compressed Ba 2 CuO 4 leads to an inverted Cu 3d e g complex with the d x 2 -y 2 orbital sitting below the d 3z 2 - r 2 and an electronic structure highly unusual compared to the conventional cuprates. We construct a two-orbital Hubbard model for the Cu d 9 state at hole doping x = 2δ and study the orbital-dependent strong correlation and superconductivity. For the undoped case at x = 0 , we found that strong correlation drives an orbital-polarized Mott-insulating state with the spin-1/2 moment of the localized d 3z 2 - r 2 orbital. In contrast to the single-band cuprates where superconductivity is suppressed in the overdoped regime, hole doping the two-orbital Mott insulator leads to orbital-dependent correlations and the robust spin and orbital exchange interactions produce a high-T c antiphase d-wave superconductor even in the heavily doped regime at x = 0.4 . We conjecture that Ba 2 CuO 3+δ realizes mixtures of such heavily hole-doped superconducting Ba 2 CuO 4 and disordered Ba 2 CuO 3 chains in a single-layer or predominately separated bilayer structure. Our findings suggest that unconventional cuprates with liberated orbitals as doped two-band Mott insulators can be a direction for realizing high-T c superconductivity with enhanced transition temperature T c .

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tuning structural, transport, and magnetic properties of epitaxial SrRu O 3 through Ba substitution

The perovskite ruthenates (A RuO 3 , A=Ca, Ba, or Sr) exhibit unique properties owing to a subtle interplay of crystal structure and electronic-spin degrees of freedom. Here, in this study, we demonstrate an intriguing continuous tuning of crystal symmetry from orthorhombic to tetragonal (no octahedral rotations) phases in epitaxial SrRuO 3 achieved via Ba substitution (Sr 1-x Ba x RuO 3 with 0 ≤ x ≤ 0.7 ). An initial Ba substitution to SrRuO 3 not only changes the ferromagnetic properties, but also tunes the perpendicular magnetic anisotropy via flattening the Ru–O–Ru bond angle (to 180°), resulting in the maximum Curie temperature and an extinction of RuO 6 rotational distortions at x≈0.20. For x ≤ 0.2, the reduction of RuO 6 octahedral rotational distortion dominantly enhances the ferromagnetism in the system, though competing with the effect of the RuO 6 tetragonal distortion. Further increasing Ba substitution (x > 0.2) gradually enhances the tetragonal-type distortion, resulting in the tuning of Ru-4d orbital occupancy and suppression of ferromagnetism. Our results demonstrate that isovalent substitution of the A-site cations significantly and controllably impacts both electronic and magnetic properties of perovskite oxides.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Anomalous neutron yields confirmed for Ba-Mo and newly observed for Ce-Zr from spontaneous fission of Cf 252

We reinvestigated the neutron multiplicity yields of Ba-Mo, Ce-Zr, Te-Pd, and Nd-Sr from the spontaneous fission of 252 Cf by (i) using both γ -γ -γ -γ and γ -γ -γ coincidence data, (ii) using up to date level scheme structures, and (iii) crosschecking analogous energy transitions in multiple isotopes, we have achieved higher precision than previous analyses. Particular attention was given to the Ba-Mo pairs where our results clearly confirm that the Ba-Mo yield data have a second hot fission mode where 8–10, and now 11 neutron evaporation channels are observed. These are the first observations of the 11 neutron channel. These 8–11 neutron channels are observed for the first time in the Ce-Zr pairs, but are not observed in other fission pairs. The measured intensities of the second mode in Ba-Mo and Ce-Zr pairs are ~1.5(4)% and ~1.0(3)%, respectively. These high neutron number evaporation modes can be an indication of hyperdeformation and/or octupole deformation in 143-145 Ba and in 146,148 Ce at scission to give rise to such high neutron multiplicities.

252-Cf↗
DOE OSTI2021

Iridium valence variation and carrier sign tuning in ( Ca , Ba ) x La 2 – x CuIrO 6 double perovskites

Here, we report the structure and properties of ( Ca , Ba ) x La 2 – x CuIrO 6 . The rock-salt double perovskite structure goes through a P 1 ¯ to P 2 1 / n phase transition with increasing Ba content but not with Ca content. In both cases, the Ir ion is oxidized from 4 + to 5 + with increasing substitution. Transport and magnetic properties measurements reveal that all compositions are insulating with hysteretic spin-freezing magnetic behavior. Seebeck coefficient measurements reveal a large thermopower change from + 176 μ V /K in La 2 CuIrO 6 to – 223 μ V /K with increasing Ba content in Ba x La 2 – x CuIrO 6 . This behavior is modeled well by the Heikes formula for correlated hopping conduction. ( Ca , Ba ) x La 2 – x CuIrO 6 provides a model system for investigations of other systems with similar carrier sign tuning, with applications toward semiconductors and thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesis, structural characterization, and electronic structure of the novel Zintl phase Ba 2 ZnP 2

The novel Zintl phase dibarium zinc diphosphide (Ba 2 ZnP 2 ) was synthesized for the first time. This was accom­plished using the Pb flux technique, which allowed for the growth of crystals of adequate size for structural determination via single-crystal X-ray diffraction methods. The Ba 2 ZnP 2 com­pound was determined to crystallize in a body-centered ortho­rhom­bic space group, Ibam (No. 72). Formally, this crystallographic arrangement belongs to the K 2 SiP 2 structure type. Therefore, the structure can be best described as infinite [ZnP 2 ] 4– polyanionic chains with divalent Ba 2+ cations located between the chains. All valence electrons are partitioned, which conforms to the Zintl–Klemm concept and suggests that Ba 2 ZnP 2 is a valence-precise com­position. In conclusion, the electronic band structure of this new com­pound, com­puted with the aid of the TB–LMTO–ASA code, shows that Ba 2 ZnP 2 is an intrinsic semiconductor with a band gap of ca 0.6 eV.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Ion Manipulation from Liquid Xe to Vacuum: Ba-Tagging for a nEXO Upgrade and Future 0 νββ Experiments

Neutrinoless double beta decay (0𝜈𝛽𝛽) provides a way to probe physics beyond the Standard Model of particle physics. The upcoming nEXO experiment will search for 0𝜈𝛽𝛽 decay in 136 Xe with a projected half-life sensitivity exceeding 10 28 years at the 90% confidence level using a liquid xenon (LXe) Time Projection Chamber (TPC) filled with 5 tonnes of Xe enriched to ∼90% in the 𝛽𝛽-decaying isotope 136 Xe. In parallel, a potential future upgrade to nEXO is being investigated with the aim to further suppress radioactive backgrounds and to confirm 𝛽𝛽-decay events. This technique, known as Ba-tagging, comprises extracting and identifying the 𝛽𝛽-decay daughter 136 Ba ion. One tagging approach being pursued involves extracting a small volume of LXe in the vicinity of a potential 𝛽𝛽-decay using a capillary tube and facilitating a liquid-to-gas phase transition by heating the capillary exit. The Ba ion is then separated from the accompanying Xe gas using a radio-frequency (RF) carpet and RF funnel, conclusively identifying the ion as 136 Ba via laser-fluorescence spectroscopy and mass spectrometry. Simultaneously, an accelerator-driven Ba ion source is being developed to validate and optimize this technique. The motivation for the project, the development of the different aspects, along with the current status and results, are discussed here.

a-tagging↗
DOE OSTI2020

Materials Data on Ba(MgBi)2 by Materials Project

Ba(MgBi)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ba is bonded to six equivalent Bi atoms to form BaBi6 octahedra that share corners with twelve equivalent MgBi4 tetrahedra, edges with six equivalent BaBi6 octahedra, and edges with six equivalent MgBi4 tetrahedra. All Ba–Bi bond lengths are 3.60 Å. Mg is bonded to four equivalent Bi atoms to form MgBi4 tetrahedra that share corners with six equivalent BaBi6 octahedra, corners with six equivalent MgBi4 tetrahedra, edges with three equivalent BaBi6 octahedra, and edges with three equivalent MgBi4 tetrahedra. The corner-sharing octahedra tilt angles range from 19–52°. All Mg–Bi bond lengths are 3.00 Å. Bi is bonded to three equivalent Ba and four equivalent Mg atoms to form a mixture of distorted corner and edge-sharing BiBa3Mg4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Mo3O5)2 by Materials Project

BaMo6O10 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Ba–O bond distances ranging from 2.81–3.37 Å. In the second Ba2+ site, Ba2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Ba–O bond distances ranging from 2.79–3.38 Å. In the third Ba2+ site, Ba2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Ba–O bond distances ranging from 2.79–3.40 Å. In the fourth Ba2+ site, Ba2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Ba–O bond distances ranging from 2.83–3.40 Å. There are twenty-four inequivalent Mo3+ sites. In the first Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.95–2.17 Å. In the second Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.00–2.21 Å. In the third Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.10–2.18 Å. In the fourth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.96–2.18 Å. In the fifth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.96–2.17 Å. In the sixth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.09–2.16 Å. In the seventh Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.08–2.18 Å. In the eighth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.95–2.16 Å. In the ninth Mo3+ site, Mo3+ is bonded to five O2- atoms to form corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.01–2.16 Å. In the tenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.92–2.10 Å. In the eleventh Mo3+ site, Mo3+ is bonded to five O2- atoms to form corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.93–2.12 Å. In the twelfth Mo3+ site, Mo3+ is bonded to five O2- atoms to form corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.92–2.14 Å. In the thirteenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.08–2.18 Å. In the fourteenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.07–2.18 Å. In the fifteenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.09–2.20 Å. In the sixteenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.07–2.20 Å. In the seventeenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.05–2.19 Å. In the eighteenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.09–2.22 Å. In the nineteenth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.10–2.20 Å. In the twentieth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.01–2.16 Å. In the twenty-first Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.10–2.19 Å. In the twenty-second Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.07–2.18 Å. In the twenty-third Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.07–2.16 Å. In the twenty-fourth Mo3+ site, Mo3+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 2.07–2.18 Å. There are forty inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted L-shaped geometry to two Ba2+ and two Mo3+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Mo3+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Mo3+ atoms. In the fourth O2- site, O2- is bonded in a distorted L-shaped geometry to two Ba2+ and two Mo3+ atoms. In the fifth O2- site, O2- is bonded in a distorted L-shaped geometry to two Ba2+ and two Mo3+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Mo3+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Mo3+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Mo3+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirteenth O2- site, O2- is bonded in a see-saw-like geometry to one Ba2+ and four Mo3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ba2+ and four Mo3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ba2+ and four Mo3+ atoms. In the sixteenth O2- site, O2- is bonded in a see-saw-like geometry to one Ba2+ and four Mo3+ atoms. In the seventeenth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted see-saw-like geometry to one Ba2+ and four Mo3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ba2+ and four Mo3+ atoms. In the twentieth O2- site, O2- is bonded in a see-saw-like geometry to one Ba2+ and four Mo3+ atoms. In the twenty-first O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-second O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-third O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the twenty-ninth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirtieth O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirty-first O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirty-second O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirty-third O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirty-fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ba2+ and three Mo3+ atoms. In the thirty-fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ba2+ and three Mo3+ atoms. In the thirty-sixth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to one Ba2+ and three Mo3+ atoms. In the thirty-seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirty-eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the thirty-ninth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+ and three Mo3+ atoms. In the fortieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ba2+ and four Mo3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(HO)2 by Materials Project

Ba(OH)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 2-coordinate geometry to five H1+ and seven O2- atoms. There are a spread of Ba–H bond distances ranging from 2.68–2.91 Å. There are a spread of Ba–O bond distances ranging from 2.72–3.04 Å. In the second Ba2+ site, Ba2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Ba–O bond distances ranging from 2.64–2.71 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to two equivalent Ba2+ and one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one Ba2+ and one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one Ba2+ and one O2- atom. The H–O bond length is 0.97 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one Ba2+ and one O2- atom. The H–O bond length is 0.98 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to three Ba2+ and one H1+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to three Ba2+ and one H1+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to two Ba2+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to two equivalent Ba2+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Ge3Pt)4 by Materials Project

Ba(PtGe3)4 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Ba is bonded to twelve equivalent Ge atoms to form BaGe12 cuboctahedra that share faces with eight equivalent PtGe6 octahedra. All Ba–Ge bond lengths are 3.43 Å. Pt is bonded to six equivalent Ge atoms to form distorted PtGe6 octahedra that share corners with six equivalent PtGe6 octahedra and faces with two equivalent BaGe12 cuboctahedra. The corner-sharing octahedral tilt angles are 60°. All Pt–Ge bond lengths are 2.55 Å. Ge is bonded in a 2-coordinate geometry to one Ba, two equivalent Pt, and two equivalent Ge atoms. There are one shorter (2.53 Å) and one longer (2.70 Å) Ge–Ge bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(C2N3)2 by Materials Project

Ba(CN2)2(CN)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional and consists of four CN clusters and one Ba(CN2)2 framework. In each CN cluster, there are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.18 Å) and one longer (1.28 Å) C–N bond length. In the second C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.22 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a linear geometry to two C4+ atoms. In the second N3- site, N3- is bonded in a single-bond geometry to one C4+ atom. In the Ba(CN2)2 framework, Ba2+ is bonded in a distorted pentagonal planar geometry to five N3- atoms. There are a spread of Ba–N bond distances ranging from 2.78–2.89 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a bent 150 degrees geometry to two N3- atoms. There is one shorter (1.23 Å) and one longer (1.37 Å) C–N bond length. In the second C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.20 Å) and one longer (1.28 Å) C–N bond length. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted water-like geometry to one Ba2+ and two C4+ atoms. In the second N3- site, N3- is bonded in a distorted single-bond geometry to one C4+ and one N3- atom. The N–N bond length is 1.23 Å. In the third N3- site, N3- is bonded in a distorted trigonal planar geometry to two equivalent Ba2+ and one N3- atom. In the fourth N3- site, N3- is bonded in a 1-coordinate geometry to two equivalent Ba2+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(H9O5)2 by Materials Project

Ba(H3O4)2(H2)4(H2O)2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of sixteen hydrogen molecules; eight water molecules; and two Ba(H3O4)2 ribbons oriented in the (0, 1, 0) direction. In each Ba(H3O4)2 ribbon, Ba2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.43–3.17 Å. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one Ba2+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ba2+ and one O2- atom. The O–O bond length is 1.29 Å. In the third O2- site, O2- is bonded in a water-like geometry to one Ba2+ and two H1+ atoms. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one O2- atom. The O–O bond length is 1.44 Å. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom. The O–O bond length is 1.49 Å. In the sixth O2- site, O2- is bonded in a distorted L-shaped geometry to one Ba2+ and one O2- atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+ and one O2- atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CoGe)2 by Materials Project

Ba(CoGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a distorted body-centered cubic geometry to eight equivalent Ge atoms. All Ba–Ge bond lengths are 3.42 Å. Co is bonded to four equivalent Ge atoms to form a mixture of distorted corner and edge-sharing CoGe4 tetrahedra. All Co–Ge bond lengths are 2.34 Å. Ge is bonded in a 8-coordinate geometry to four equivalent Ba and four equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(TeMo)6 by Materials Project

BaMo6Te6 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. Ba is bonded in a 9-coordinate geometry to nine Te atoms. There are six shorter (3.58 Å) and three longer (3.73 Å) Ba–Te bond lengths. There are two inequivalent Mo sites. In the first Mo site, Mo is bonded in a 10-coordinate geometry to six Mo and four Te atoms. There are a spread of Mo–Mo bond distances ranging from 2.68–2.79 Å. There are a spread of Mo–Te bond distances ranging from 2.83–2.89 Å. In the second Mo site, Mo is bonded in a 10-coordinate geometry to six Mo and four Te atoms. Both Mo–Mo bond lengths are 2.66 Å. There are a spread of Mo–Te bond distances ranging from 2.83–2.90 Å. There are two inequivalent Te sites. In the first Te site, Te is bonded in a 6-coordinate geometry to two equivalent Ba and four Mo atoms. In the second Te site, Te is bonded in a 5-coordinate geometry to one Ba and four Mo atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Cd2Pt)2 by Materials Project

Ba(PtCd2)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Ba is bonded to six equivalent Pt atoms to form a mixture of distorted edge and corner-sharing BaPt6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are two shorter (3.37 Å) and four longer (3.50 Å) Ba–Pt bond lengths. Pt is bonded in a 9-coordinate geometry to three equivalent Ba and six equivalent Cd atoms. There are four shorter (2.83 Å) and two longer (2.85 Å) Pt–Cd bond lengths. Cd is bonded in a distorted trigonal non-coplanar geometry to three equivalent Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(H9O5)2 by Materials Project

Ba(HO)10(H2)4 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of sixteen hydrogen molecules and two Ba(HO)10 ribbons oriented in the (0, 1, 0) direction. In each Ba(HO)10 ribbon, Ba2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.49–2.97 Å. There are ten inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.02 Å) and one longer (1.59 Å) H–O bond length. In the third H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.66 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two H1+ atoms. In the second O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom. The O–O bond length is 1.49 Å. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+ and one O2- atom. The O–O bond length is 1.30 Å. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom. The O–O bond length is 1.42 Å. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one O2- atom. In the sixth O2- site, O2- is bonded in a water-like geometry to one Ba2+ and two H1+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three H1+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+ and one O2- atom. In the ninth O2- site, O2- is bonded in a water-like geometry to one Ba2+ and two H1+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, one H1+, and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electronic Structure, Chemical Bonding and Electrocatalytic Activity of Novel Ba(Fe0.7Ta0.3)O3-d Compounds

Ba(Fe0.7Ta0.3)O3-d (BFTO) compounds were synthesized using conventional, high-temperature solid-state ceramic reaction method by varying the sintering temperature (Ts=1200-1350 °C). The crystal structure, electronic structure and electrocatalytic activity of BFTO compounds were evaluated. Processing temperature induced phase transformations and structural quality influences the electronic structure and electrocatalytic activity of BFTO compounds. At Ts=1200 oC, Ba(Fe0.7Ta0.3)O3-d stabilizes in mixed phase of orthorhombic + rhombohedral phase (Amm2 + R3m). With increasing Ts (=1250 oC), Ba(Fe0.7Ta0.3)O3-d ceramics stabilize in tetragonal + rhombohedral [P4mm + R3m] mixed phase with a variation in the quantity of respective phases. High-resolution X-ray photoelectron spectroscopy of constituent elements, namely, Ba 3d, Fe2p, Ta 4f and O 1s reveal the electronic structure changes due to changes in chemical environment resulted from structural transformation. The electrocatalytic activity of BFTO was evaluated towards hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Though all the samples demonstrated appreciable electrocatalytic properties, the best electrochemical catalytic activity was shown by BFTO samples sintered at 1350 °C. BFTO-1350 oC showed an onset potential of -0.690 V vs. RHE for HER and an onset potential of 0.73 V vs. RHE for ORR indicating its significant electrocatalytic performance. A general increase in activity with sintering temperature is potentially due to the improved structural quality of the BFTO ceramics. In addition to offering the fundamental insights into solid state materials based on doped BaTiO3 for electrocatalysis, the present work may contribute to the design and development of materials for high-temperature electrocatalytic converters.

Ba(Fe0.7Ta0.3)O3-d, Phase Transformation↗