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DOE OSTI2020

Materials Data on Ba(HoTe2)2 by Materials Project

Ba(HoTe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.56–3.75 Å. There are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing HoTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Ho–Te bond distances ranging from 3.05–3.13 Å. In the second Ho3+ site, Ho3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing HoTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Ho–Te bond distances ranging from 3.05–3.12 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Ho3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Ho3 trigonal bipyramids. In the second Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Ho3 square pyramids. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Ho3+ atoms. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Ho3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(HoS2)2 by Materials Project

Ba(HoS2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Ba–S bond distances ranging from 3.21–3.39 Å. There are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to six S2- atoms to form a mixture of edge and corner-sharing HoS6 octahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are one shorter (2.69 Å) and five longer (2.76 Å) Ho–S bond lengths. In the second Ho3+ site, Ho3+ is bonded to six S2- atoms to form a mixture of edge and corner-sharing HoS6 octahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Ho–S bond distances ranging from 2.71–2.77 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Ho3+ atoms. In the second S2- site, S2- is bonded to two equivalent Ba2+ and three equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing SBa2Ho3 square pyramids. In the third S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Ho3+ atoms. In the fourth S2- site, S2- is bonded to two equivalent Ba2+ and three equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing SBa2Ho3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoH9C5(NO4)2 by Materials Project

HoC5H9(NO4)2 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.30–2.45 Å. There are three inequivalent C2+ sites. In the first C2+ site, C2+ is bonded in a trigonal planar geometry to one N3-, one H1+, and one O2- atom. The C–N bond length is 1.32 Å. The C–H bond length is 1.10 Å. The C–O bond length is 1.25 Å. In the second C2+ site, C2+ is bonded in a trigonal planar geometry to one H1+ and two O2- atoms. The C–H bond length is 1.11 Å. There is one shorter (1.26 Å) and one longer (1.28 Å) C–O bond length. In the third C2+ site, C2+ is bonded in a trigonal planar geometry to one H1+ and two equivalent O2- atoms. The C–H bond length is 1.10 Å. Both C–O bond lengths are 1.28 Å. N3- is bonded in a trigonal planar geometry to one C2+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. There are five inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one Ho3+ and one C2+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Ho3+ and one C2+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+ and one C2+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one Ho3+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Oxide Two‐Dimensional Electron Gas with High Mobility at Room‐Temperature

Abstract The prospect of 2‐dimensional electron gases (2DEGs) possessing high mobility at room temperature in wide‐bandgap perovskite stannates is enticing for oxide electronics, particularly to realize transparent and high‐electron mobility transistors. Nonetheless only a small number of studies to date report 2DEGs in BaSnO 3 ‐based heterostructures. Here, 2DEG formation at the LaScO 3 /BaSnO 3 (LSO/BSO) interface with a room‐temperature mobility of 60 cm 2 V −1 s −1 at a carrier concentration of 1.7 × 10 13 cm –2 is reported. This is an order of magnitude higher mobility at room temperature than achieved in SrTiO 3 ‐based 2DEGs. This is achieved by combining a thick BSO buffer layer with an ex situ high‐temperature treatment, which not only reduces the dislocation density but also produces a SnO 2 ‐terminated atomically flat surface, followed by the growth of an overlying BSO/LSO interface. Using weak beam dark‐field transmission electron microscopy imaging and in‐line electron holography technique, a reduction of the threading dislocation density is revealed, and direct evidence for the spatial confinement of a 2DEG at the BSO/LSO interface is provided. This work opens a new pathway to explore the exciting physics of stannate‐based 2DEGs at application‐relevant temperatures for oxide nanoelectronics.

2-dimensional electron gas↗
DOE OSTI2020

Materials Data on KHo(WO4)2 by Materials Project

KHo(WO4)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.86–3.11 Å. Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.26–2.30 Å. W6+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing WO6 octahedra. The corner-sharing octahedral tilt angles are 43°. There are a spread of W–O bond distances ranging from 1.83–2.13 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one K1+, one Ho3+, and two equivalent W6+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent K1+ and two equivalent W6+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Ho3+, and one W6+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Ho3+, and one W6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho4BClO7 by Materials Project

Ho4BO7Cl crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.22–2.35 Å. In the second Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to six O2- and one Cl1- atom. There are a spread of Ho–O bond distances ranging from 2.26–2.38 Å. The Ho–Cl bond length is 2.96 Å. In the third Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.25–2.76 Å. In the fourth Ho3+ site, Ho3+ is bonded in a 5-coordinate geometry to five O2- and one Cl1- atom. There are a spread of Ho–O bond distances ranging from 2.20–2.34 Å. The Ho–Cl bond length is 2.88 Å. B3+ is bonded in a trigonal planar geometry to three O2- atoms. All B–O bond lengths are 1.38 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of distorted corner and edge-sharing OHo4 tetrahedra. In the second O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Ho3+ and one B3+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ho3+ and one B3+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the sixth O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. In the seventh O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. Cl1- is bonded in a 2-coordinate geometry to two Ho3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Twin-Domain Formation in Epitaxial Triangular Lattice Delafossites

Twin domains are often found as structural defects in symmetry mismatched epitaxial thin films. The delafossite ABO 2 , which has a rhombohedral structure, is a good example that often forms twin domains. Although bulk metallic delafossites are known to be the most conducting oxides, high conductivity is yet to be realized in thin film forms. Suppressed conductivity found in thin films is mainly caused by the formation of twin domains, and their boundaries can be a source of scattering centers for charge carriers. To overcome this challenge, the underlying mechanism for their formation must be understood so that such defects can be controlled and eliminated. Here, we report the origin of structural twins formed in a CuCrO 2 delafossite thin film on a substrate with hexagonal or triangular symmetries. A robust heteroepitaxial relationship is found for the delafossite film with the substrate, and the surface termination turns out to be critical to determine and control the domain structure of epitaxial delafossites. Based on such discoveries, we also demonstrate twin-free epitaxial thin films grown on high-miscut substrates. Finally, this finding provides an important synthesis strategy for growing single-domain delafossite thin films and can be applied to other delafossites for the epitaxial synthesis of high-quality thin films.

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

New sterically hindered polyvinylamine-containing membranes for CO 2 capture from flue gas

Amine-containing facilitated transport membranes can have both high permeability and selectivity due to the reversible reaction between CO 2 and amino groups for effective carbon capture from flue gas. In this study, we have developed an improved method for the synthesis of high-molecular-weight sterically hindered polyvinylamine (PVAm) as the new fixed-site carrier in thin-film composite membranes for CO 2 capture. Commercially available PVAm was N-monomethylated into poly-N-methyl-N-vinylamine (PVAm-CH 3 ) using the stepwise reductive amination with a highly polar fluorinated alcohol as the solvent to enhance the equilibrium shift to the formation of the imine intermediate. The method prevented over-alkylation, resulting in the increased yield of the target product. PVAm-CH 3 exhibited excellent CO 2 facilitation with a CO 2 permeability of 445.7 Barrer (1 Barrer = 3.349 x 10 –16 mol m m –2 s –1 Pa –1 ) and a CO 2 /N 2 selectivity of 70.3, which are above the Robeson 2008 upper bound. The PVAm-CH 3 solution retained a sufficiently high viscosity after incorporating the aminoacid salt, 2-(1-piperazinyl)ethylamine sarcosinate (PZEA-Sar), as the mobile carrier for the membrane coating on nanoporous polyethersulfone (PES) substrates without any penetration issues. The resultant thin-film composite PVAm-CH3/PZEA-Sar membrane with a thickness of approximately 170 nm exhibited a superior CO 2 performance of 1071 GPU (1 GPU = 3.349 x 10 –10 mol m –2 s –1 Pa –1 ) and a CO 2 /N 2 selectivity of 183 at 57°C and a feed gas pressure of 111.64 kPa (1.5 psig). This PVAm-CH 3 /PZEA-Sar membrane surpassed the latest redefined 2019 CO 2 /N 2 upper bound and outperformed other polymer-based membranes. Density functional theory calculations also demonstrated that PVAm-CH 3 showed a stronger preference, relative to PVAm, toward the more efficient bicarbonate pathway. Thus, the steric hindrance effect of PVAm-CH 3 enhanced the solubility of CO 2 in the polymer matrix and resulted in the higher CO 2 permeance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

13 C NMR study of amino acid salts in facilitated transport membranes for post-combustion carbon capture

Some of amino acid salts (AASs) have been demonstrated to be effective mobile carriers in facilitated transport membranes (FTMs) to achieve superior CO 2 permeance and CO 2 /N 2 selectivity for CO 2 capture from flue gas. Understandings of how the structures of different AASs affect the chemistry of the amine–CO 2 reaction are essential for the future development of more efficient AAS mobile carriers. In this study, the reaction chemistry of selected AASs with CO 2 was investigated by 13 C nuclear magnetic resonance (NMR) spectroscopy. The CO 2 loading and the distribution of major reaction products, including carbamate and bicarbonate products of each studied AAS were quantitatively analyzed. The positive correlation between the CO 2 loading of AAS (mol CO 2 /g AAS) and the CO 2 permeance of FTMs suggested that AAS with a higher CO 2 loading may improve the performance of FTMs. Our results also showed that increasing the steric hindrance of AAS could be a practical way to promote the bicarbonate reaction pathway and thus potentially increase the CO 2 loading (mol CO 2 /mol AAS). Moreover, 2-(1-piperazinyl)ethylamine (PZEA) was found to be a more effective multi-amine than piperazine (PZ) for synthesizing AASs due to the presence of more effective nitrogen sites per molecule. The superior CO 2 permeance of the PZEA-Sar membrane is also attributed to its more uniform membrane formation. As a result, the knowledge gained from this study will inform the rational design of more effective AAS carriers for CO 2 capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1999

Stratospheric Tracers of Atmospheric Transport (STRAT) Campaign: ER-2 Participation

The NASA Stratospheric Tracers of Atmospheric Transport (STRAT) mission was initiated to advance knowledge of the major transport mechanisms of the upper troposphere-lower stratosphere. This is the region of the atmosphere within which exchange processes take place that critically determine the response of the climate system and ozone distribution to changing conditions triggered by the release of chemicals at the surface. The mission series that extended from October 1995 to November 1997 was extremely successful. The scientific advances that emerged from that mission include analyses of: (1) troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O, and O3; (2) the effects of tropical cirrus clouds on the abundance of lower stratospheric ozone; (3) the role of HO(sub x) in super- and subsonic aircraft exhaust plumes; and (4) dehydration and denitrification in the arctic polar vortex during the 1995-96 winter. The abstracts from published papers are included.

Anderson, James G.↗
NASA NTRS1999

ASCA Observations of "Type 2" LINERs Evidence for a Stellar Source of Ionization

We present ASCA observations of LINERs without broad H.alpha emission in their optical spectra. The sample of "type 2" LINERs consists of NGC 404, 4111, 4192, 4457, and 4569. We have detected X-ray emission from all the objects except for NGC 404; among the detected objects are two so-called transition objects (NGC 4192 and NGC 4569), which have been postulated to be composite nuclei having both an H II region and a LINER component. The images of NGC 4111 and NGC 4569 in the soft (0.5-2 keV) and hard (2-7 keV) X-ray bands are extended on scales of several kpc. The X-ray spectra of NGC 4111, NGC 4457 and NGC 4569 are well fitted by a two-component model that consists of soft thermal emission with kT approximately 0.65 keV and a hard component represented by a power law (photon index approximately 2) or by thermal bremsstrahlung emission (kT approximately several keV). The extended hard X-rays probably come from discrete sources, while the soft emission most likely originates from hot gas produced by active star formation in the host galaxy. We have found no clear evidence for the presence of active galactic nuclei (AGNs) in the sample. Using black hole masses estimated from host galaxy bulge luminosities, we obtain an upper limit on the implied Eddington ratios less than 5 x 10(exp -5). If an AGN component is the primary ionization source of the optical emission lines, then it must be heavily obscured with a column density significantly larger than 10(exp 23)/sq cm, since the observed X-ray luminosity is insufficient to drive the luminosities of the optical emission lines. Alternatively, the optical emission could be ionized by a population of exceptionally hot stars. This interpretation is consistent with the small [O I] lambda6300/H.alpha ratios observed in these sources, the ultraviolet spectral characteristics in the cases where such information exists, and the X-ray results reported here. We also analyze the X-ray properties of NGC 4117, a low-luminosity Seyfert 2 galaxy serendipitously observed in the field of NGC 4111.

Terashima, Yuichi↗
DOE OSTI2020

Materials Data on RbHo(MoO4)2 by Materials Project

RbHo(MoO4)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Rb1+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Rb–O bond distances ranging from 2.83–3.38 Å. Ho3+ is bonded in a 6-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.29–2.71 Å. Mo6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.79–2.41 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Rb1+ and two equivalent Mo6+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one Rb1+, two equivalent Ho3+, and one Mo6+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Rb1+, one Ho3+, and two equivalent Mo6+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Rb1+, one Ho3+, and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KHo(MoO4)2 by Materials Project

KHo(MoO4)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of K–O bond distances ranging from 2.78–3.37 Å. Ho3+ is bonded in a 6-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.70 Å. Mo6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.79–2.42 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and two equivalent Mo6+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, two equivalent Ho3+, and one Mo6+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Ho3+, and two equivalent Mo6+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+, one Ho3+, and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RbHo(MoO4)2 by Materials Project

RbHo(MoO4)2 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Rb1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Rb–O bond distances ranging from 2.85–3.08 Å. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.58 Å. Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.76–1.86 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one Ho3+, and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Rb1+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb2NaHoF6 by Materials Project

Rb2NaHoF6 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. Rb1+ is bonded to twelve F1- atoms to form distorted RbF12 cuboctahedra that share corners with twelve equivalent RbF12 cuboctahedra, faces with six equivalent RbF12 cuboctahedra, faces with four equivalent NaF6 octahedra, and faces with four equivalent HoF6 octahedra. There are a spread of Rb–F bond distances ranging from 3.00–3.38 Å. Na1+ is bonded to six F1- atoms to form NaF6 octahedra that share corners with six equivalent HoF6 octahedra and faces with eight equivalent RbF12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–14°. All Na–F bond lengths are 2.34 Å. Ho3+ is bonded to six F1- atoms to form HoF6 octahedra that share corners with six equivalent NaF6 octahedra and faces with eight equivalent RbF12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–14°. All Ho–F bond lengths are 2.17 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted linear geometry to four equivalent Rb1+, one Na1+, and one Ho3+ atom. In the second F1- site, F1- is bonded in a 2-coordinate geometry to four equivalent Rb1+, one Na1+, and one Ho3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrHo2Al2O7 by Materials Project

Ho2SrAl2O7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight equivalent AlO6 octahedra. There are four shorter (2.63 Å) and eight longer (2.80 Å) Sr–O bond lengths. Ho3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ho–O bond distances ranging from 2.19–2.67 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with five equivalent AlO6 octahedra and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Al–O bond distances ranging from 1.87–2.11 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Sr2+, two equivalent Ho3+, and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded to four equivalent Sr2+ and two equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OSr4Al2 octahedra. The corner-sharing octahedral tilt angles are 0°. In the third O2- site, O2- is bonded in a 2-coordinate geometry to five equivalent Ho3+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaHo(CoO3)2 by Materials Project

BaHo(CoO3)2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with four equivalent BaO12 cuboctahedra, corners with eight equivalent HoO12 cuboctahedra, faces with two equivalent HoO12 cuboctahedra, faces with four equivalent BaO12 cuboctahedra, and faces with eight equivalent CoO6 octahedra. There are four shorter (2.70 Å) and eight longer (2.97 Å) Ba–O bond lengths. Ho3+ is bonded to twelve O2- atoms to form HoO12 cuboctahedra that share corners with four equivalent HoO12 cuboctahedra, corners with eight equivalent BaO12 cuboctahedra, faces with two equivalent BaO12 cuboctahedra, faces with four equivalent HoO12 cuboctahedra, and faces with eight equivalent CoO6 octahedra. There are eight shorter (2.53 Å) and four longer (2.70 Å) Ho–O bond lengths. Co+3.50+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six equivalent CoO6 octahedra, faces with four equivalent BaO12 cuboctahedra, and faces with four equivalent HoO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Co–O bond distances ranging from 1.92–2.01 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ho3+ and two equivalent Co+3.50+ atoms. In the second O2- site, O2- is bonded to four equivalent Ba2+ and two equivalent Co+3.50+ atoms to form a mixture of edge and corner-sharing OBa4Co2 octahedra. The corner-sharing octahedral tilt angles are 0°. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Ho3+, and two equivalent Co+3.50+ atoms.

36 MATERIALS SCIENCE↗