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DOE OSTI2024

Resilience of the Aurivillius structure upon La and Cr doping in a Bi 5 Ti 3 FeO 15 multiferroic

Here, combining the experimental techniques of high-resolution X-ray diffraction, magnetometry, specific heat measurement, and X-ray photoelectron, Raman and dielectric spectroscopy techniques, we have studied the influence of La and Cr doping on the crystal structure and magnetism of the room temperature Aurivillius multiferroic Bi 5 Ti 3 FeO 15 by investigating the physical properties of (Bi 4 La)Ti 3 FeO 15 and Bi 5 Ti 3 (Fe 0.5 Cr 0.5 )O 15 . The parent (Bi 5 Ti 3 FeO 15 ) and the doped ((Bi 4 La)Ti 3 FeO 15 and Bi 5 Ti 3 (Fe 0.5 Cr 0.5 )O 15 ) compounds crystallize in the A2 1 am space group, which is confirmed through our analysis of high-resolution synchrotron X-ray diffraction data obtained on phase-pure polycrystalline powders. We determined the oxidation states of the metal atoms in the studied compounds as Fe 3+ , Ti 4+ , Cr 3+ , and La 3+ through the analysis of X-ray photoelectron spectroscopy data. The magnetic susceptibilities of the three compounds are marked by the absence of a long-range ordered ground state, but dominated by superparamagnetic clusters with dominant antiferromagnetic interactions. This signature of short-range magnetism is also seen in specific heat as a low temperature enhancement which is suppressed upon the application of external magnetic fields up to 8 T. Our dielectric spectroscopy experiments showed that the three studied compounds display similar features in the dielectric constant measured as a function of frequency. However, upon doping La at the Bi site, the width of the ferroelectric hysteresis loop increases for (Bi 4 La)Ti 3 FeO 15 compared to that of the parent compound Bi 5 Ti 3 FeO 15 , and with Cr doping, Bi 5 Ti 3 (Fe 0.5 Cr 0.5 )O 15 becomes a leaky dielectric. The resilience of the Aurivillius crystal structure towards doping of La at the Bi site and Cr at the Fe site is clearly seen in the bulk properties of magnetic susceptibility, specific heat and the average crystal structure. The relevance of changes in the local structure is evident from our Raman spectroscopy and X-ray pair distribution function studies.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Young’s modulus of V 3 O 5 thin films

Vanadium oxide V 3 O 5 exhibits an insulator-to-metal transition (IMT) near 430 K, which is the highest value for all vanadium oxides exhibiting IMTs. This makes it interesting for advanced electronic applications. However, the properties of V 3 O 5 have been little studied, and, in particular, there are no reports of experimentally determined mechanical properties. In this work, Young’s modulus of sputter-deposited V 3 O 5 thin films has been determined by measuring the fundamental resonant frequency of V 3 O 5 -coated silicon microcantilevers using a laser beam deflection technique. After deposition, the films were characterized by x-ray diffraction, resistivity measurements, and atomic force microscopy. The value of Young’s modulus experimentally determined for V 3 O 5 was 198 ± 14 GPa, which is slightly lower than the computationally derived values for bulk crystal V 3 O 5 .

36 MATERIALS SCIENCE↗
DOE OSTI2025

High-frequency electrical behavior in V 3 O 5 thin films

Vanadium oxides are known for their metal–insulator transition (MIT), with V 3 O 5 being notable for its transition temperature exceeding room temperature. At about 430 K, this material shows a change in crystal symmetry accompanied with one order of magnitude increase in its electrical conductivity and alterations in its optical properties. Although the property changes during the MIT in V 3 O 5 are less pronounced than those observed in VO 2 , its transition temperature is 90 K higher, making it appealing for applications requiring elevated temperatures. In this article, the high-frequency characteristics were determined in a V 3 O 5 two-terminal device in the range from 5 to 35 GHz. The S-parameters showed that the return loss at room temperature was close to −1.5 dB, and the isolation between ports was approximately −50 dB. At temperatures above the metal–insulator transition, the isolation decreased to around −40 dB at 35 GHz. For S11 and S22, similar behavior was observed at room temperature, with a notable change in the S-parameter phase of the device. This behavior suggests that V 3 O 5 may function well as a capacitor because the considerable change in phase could control the flow of electrical signals in devices. This property also may be used for matching purposes, especially considering its response to temperature changes. Additionally, conductivity calculation from S-parameters shows a decrease of approximately two orders of magnitude at 500 K and one order of magnitude at 300 K compared to DC values. These findings highlight V 3 O 5 potential for integration into radio frequency devices that demand consistent performance in high-temperature environments.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Quantum scattering of HC 5 N and para -H 2 on a new potential energy surface

In the interstellar medium (ISM), non-local thermodynamic equilibrium situations are common due to low density, and one needs to consider the effect of molecular collisions in order to interpret the observations. Among the species detected in the ISM, cyanopolyynes, with the general molecular formula HC 2n+1 N (n = 1, 2, …), are characterized by large dipole moments and small rotational constants and constitute an indispensable class of candidates for the sensitive tracers of local density and temperature. We present a study of the collisional (de-) excitation of HC 5 N by para -H 2 (p-H 2 ) in its ground rotational state, namely HC 5 N ( j 1 ) + H 2 ( j 2 = 0) → HC 5 N (j$_1^′$) + H2 (j$_2^′$ = 0), where j 1 (or j$_1^′$) and j 2 (or j$_2^′$) denote the initial (or final) rotational quantum numbers of HC 5 N and H 2 , respectively. We performed the quantum scattering calculations at low collision energy using a new four-dimensional ab initio potential energy surface. In the regime where p-H 2 remains in its rotational ground state, converged cross sections did not require including excited rotational states of p-H 2 in the rotational basis. State-to-state cross sections were computed by means of the quantum-mechanical close-coupling (CC) method and the coupled states (CS) approximation, and rate coefficients for the first 61 levels of HC 5 N were computed for the first time up to 20 K with the CC approach and up to 50 K with the CS method. CC and CS results were found to agree well at temperatures up to 20 K. Finally, these data should allow a more accurate derivation of the HC 5 N abundance in molecular clouds.

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

Cation reordering instead of phase transitions: Origins and implications of contrasting lithiation mechanisms in 1D ζ- and 2D α-V 2 O 5

Substantial improvements in cycle life, rate performance, accessible voltage, and reversible capacity are required to realize the promise of Li-ion batteries in full measure. Here, we have examined insertion electrodes of the same composition (V 2 O 5 ) prepared according to the same electrode specifications and comprising particles with similar dimensions and geometries that differ only in terms of their atomic connectivity and crystal structure, specifically two-dimensional (2D) layered α-V 2 O 5 that crystallizes in an orthorhombic space group and one-dimensional (1D) tunnel-structured ζ-V 2 O 5 crystallized in a monoclinic space group. By using particles of similar dimensions, we have disentangled the role of specific structural motifs and atomistic diffusion pathways in affecting electrochemical performance by mapping the dynamical evolution of lithiation-induced structural modifications using ex situ scanning transmission X-ray microscopy, operando synchrotron X-ray diffraction measurements, and phase-field modeling. We find the operation of sharply divergent mechanisms to accommodate increasing concentrations of Li-ions: a series of distortive phase transformations that result in puckering and expansion of interlayer spacing in layered α-V 2 O 5 , as compared with cation reordering along interstitial sites in tunnel-structured ζ-V 2 O 5 . By alleviating distortive phase transformations, the ζ-V 2 O 5 cathode shows reduced voltage hysteresis, increased Li-ion diffusivity, alleviation of stress gradients, and improved capacity retention. The findings demonstrate that alternative lithiation mechanisms can be accessed in metastable compounds by dint of their reconfigured atomic connectivity and can unlock substantially improved electrochemical performance not accessible in the thermodynamically stable phase.

25 ENERGY STORAGE↗
DOE OSTI2022

Revealing room temperature ferromagnetism in exfoliated Fe 5 GeTe 2 flakes with quantum magnetic imaging

Van der Waals (vdW) material Fe 5 GeTe 2 , with its long-range ferromagnetic ordering near room temperature, has significant potential to become an enabling platform for implementing novel spintronic and quantum devices. To pave the way for applications, it is crucial to determine the magnetic properties when the thickness of Fe 5 GeTe 2 reaches the few-layers regime. However, this is highly challenging due to the need for a characterization technique that is local, highly sensitive, artifact-free, and operational with minimal fabrication. Prior studies have indicated that Curie temperature T C can reach up to close to room temperature for exfoliated Fe 5 GeTe 2 flakes, as measured via electrical transport; there is a need to validate these results with a measurement that reveals magnetism more directly. Here, we investigate the magnetic properties of exfoliated thin flakes of vdW magnet Fe 5 GeTe 2 via quantum magnetic imaging technique based on nitrogen vacancy centers in diamond. Through imaging the stray fields, we confirm room-temperature magnetic order in Fe 5 GeTe 2 thin flakes with thickness down to 7 units cell. The stray field patterns and their response to magnetizing fields with different polarities is consistent with previously reported perpendicular easy-axis anisotropy. Furthermore, we perform imaging at different temperatures and determine the Curie temperature of the flakes at ≈300 K. These results provide the basis for realizing a room-temperature monolayer ferromagnet with Fe 5 GeTe 2 . This work also demonstrates that the imaging technique enables rapid screening of multiple flakes simultaneously as well as time-resolved imaging for monitoring time-dependent magnetic behaviors, thereby paving the way towards high throughput characterization of potential two-dimensional (2D) magnets near room temperature and providing critical insights into the evolution of domain behaviors in 2D magnets due to degradation.

2D magnet↗
DOE OSTI2022

Is Terzan 5 the remnant of a building block of the Galactic bulge? Evidence from APOGEE

ABSTRACT It has been proposed that the globular cluster-like system Terzan 5 is the surviving remnant of a primordial building block of the Milky Way bulge, mainly due to the age/metallicity spread and the distribution of its stars in the α–Fe plane. We employ Sloan Digital Sky Survey data from the Apache Point Observatory Galactic Evolution Experiment to test this hypothesis. Adopting a random sampling technique, we contrast the abundances of 10 elements in Terzan 5 stars with those of their bulge field counterparts with comparable atmospheric parameters, finding that they differ at statistically significant levels. Abundances between the two groups differ by more than 1σ in Ca, Mn, C, O, and Al, and more than 2σ in Si and Mg. Terzan 5 stars have lower [α/Fe] and higher [Mn/Fe] than their bulge counterparts. Given those differences, we conclude that Terzan 5 is not the remnant of a major building block of the bulge. We also estimate the stellar mass of the Terzan 5 progenitor based on predictions by the Evolution and Assembly of GaLaxies and their Environments suite of cosmological numerical simulations, concluding that it may have been as low as ∼3 × 108 M⊙ so that it was likely unable to significantly influence the mean chemistry of the bulge/inner disc, which is significantly more massive (∼1010 M⊙). We briefly discuss existing scenarios for the nature of Terzan 5 and propose an observational test that may help elucidate its origin.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Avoided ferromagnetic quantum critical point in pressurized La 5 Co 2 Ge 3

We present the pressure-temperature phase diagram La 5 Co 2 Ge 3 up to ~ 5 GPa, which was constructed from magnetization, resistivity, and specific heat measurements. At ambient pressure, La 5 Co 2 Ge 3 is an itinerant ferromagnet with a Curie temperature T C ~ 4 K. Upon increasing pressure up to ~ 1.7 GPa, T C is suppressed down to ~ 3 K. Upon further increasing pressure, our results suggest that La 5 Co 2 Ge 3 enters a different low-temperature ground state. The corresponding transition temperature T* has a nonmonotonic pressure dependence up to ~ 5 GPa. Our results demonstrate that the ferromagnetic quantum critical point in La 5 Co 2 Ge 3 is avoided by the appearance of a different, likely magnetically ordered, state that has an antiferromagnetic component.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Crystal Growth, Optical and Scintillation Properties of Eu 2+ -doped TlSr 2 Br 5

Crystals of undoped and Eu 2+ -doped TlSr 2 Br 5 of up to 16 mm in diameter and 50 mm in length were grown by the Vertical Bridgman technique. TlSr 2 Br 5 has the monoclinic crystal structure with space group P21/c. Its density and Z eff are 5.03 g/cm 3 and 58.6, respectively. Radioluminescence spectra of undoped and Eu 2+ -doped TlSr 2 Br 5 feature a broad emission band peaking at about 440 nm for undoped and 520 nm for Eu 2+ -doped crystals. The light yield of undoped TlSr 2 Br 5 is 42,000 ph/MeV, which increases to 55,000 ph/MeV for Eu 2+ -doped crystals. The energy resolution at 662 keV ( 137 Cs) is about 5 – 6% (FWHM). As a result, the scintillation decay of undoped and Eu 2+ -doped TlSr 2 Br 5 is of the order of 100s of nanoseconds.

Bridgman technique↗
DOE OSTI2021

Structural, vibrational, thermal, and magnetic properties of mullite-type NdMnTiO 5 ceramic

Mullite-type $R$Mn 2 O 5 ($R$ = Y, rare-earth element) ceramics are of ongoing research attention because of their interesting crystal-chemical and magnetic properties. We report nuclear and magnetic structures of NdMnTiO 5 together with its spectroscopic, thermogravimetric, and magnetic properties. The polycrystalline sample is prepared by solid-state synthesis and characterized from neutron and X-ray powder diffraction data Rietveld refinements. NdMnTiO 5 crystallizes in the orthorhombic space group $Pbam$ with metric parameter $a$ = 755.20(1) pm, $b$ = 869.91(1) pm, $c$ = 582.42(1) pm, and $V$ = 382.62(1) 10 6 pm 3 . The Mn 3+ and Ti 4+ cations are observed to be located in the octahedral and pyramidal sites, respectively. The vibrational features in these polyhedral sites are characterized by Raman and Fourier transform infrared spectroscopes. The higher decomposition temperature of NdMnTiO 5 , compared to other $R$Mn 2 O 5 phases, is explained in terms of the higher bond strength of Ti-O bonds than those of Mn-O bonds. Temperature-dependent DC magnetic susceptibility suggests a paramagnetic to antiferromagnetic phase transition at 43(1) K. Inverse susceptibility in the paramagnetic region above 120 K follows the Curie-Weiss law, resulting in a magnetic moment of 6.33(1) μ B per formula unit. Neutron diffraction data collected at 7.5 K reveal that the magnetic moments of Nd 3+ and Mn 3+ in NdMnTiO 5 are incommensurately ordered with a propagation vector $k$ = (0, 0.238, 0.117).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Spinning no-scale $${\mathcal {F}}$$-SU(5) in the right direction

Abstract The Fermi National Accelerator Laboratory (FNAL) recently announced confirmation of the Brookhaven National Lab (BNL) measurements of the $$g-2$$ g - 2 of the muon that uncovered a discrepancy with the theoretically calculated Standard Model value. We suggest an explanation for the combined BNL+FNAL 4.2 $$\sigma $$ σ deviation within the supersymmetric grand unification theory (GUT) model No-Scale $${\mathcal {F}}$$ F - $$SU(5)$$ S U ( 5 ) supplemented with a string derived TeV-scale extra $$10+\overline{10}$$ 10 + 10 ¯ vector-like multiplet and charged vector-like singlet $$(XE,XE^c)$$ ( X E , X E c ) , dubbed flippons. We introduced these vector-like particles into No-Scale Flipped SU (5) many years ago, and as a result, the renormalization group equation (RGE) running was immediately shaped to produce a distinctive and rather beneficial two-stage gauge coupling unification process to avoid the Landau pole and lift unification to the string scale, in addition to contributing through 1-loop to the light Higgs boson mass. The flippons have long stood ready to tackle another challenge, and now do so yet again, where the charged vector-like “lepton”/singlet couples with the muon, the supersymmetric down-type Higgs $$H_d$$ H d , and a singlet S , using a chirality flip to easily accommodate the muonic $$g-2$$ g - 2 discrepancy in No-Scale $${\mathcal {F}}$$ F - $$SU(5)$$ S U ( 5 ) . Considering the phenomenological success of this string derived model over the prior 11 years that remains accommodative of all presently available LHC limits plus all other experimental constraints, including no fine-tuning, and the fact that for the first time a Starobinsky-like inflationary model consistent with all cosmological data was derived from superstring theory in No-Scale Flipped SU (5), we believe it is imperative to reconcile the BNL+FNAL developments within the model space.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Perform Life Cycle Energy and GHG Emission Analysis, Select Candidate Refrigerant(s), Developing Heat Pump by Using Low-GWP Refrigerants and 5 mm Diameter Tubes

Reducing environmental impacts from the energy conversion systems has been an important research topic due to recent severe global climate changes. In residential buildings, the space heating and cooling are main energy consumers, which are relying on vapor compression based heat pumps. To mitigate the environmental impacts of residential systems, the heat pumps using low-GWP refrigerants and 5mm-tube heat exchangers are proposed to replace the conventional 9 mm or 7 mm tube heat exchangers. This research uses a simulation-based design method to optimize the refrigerant circuitries of a 5-ton low-GWP refrigerant heat pumps whose indoor and outdoor heat exchangers adopt 5 mm tubes. Heat pump systems using four commercially available low-GWP refrigerants (R454A, R454C, ARM20A and ARM20B) are optimized and compared with the baseline R410A system. The results indicate that directly replacing 9 mm tubes into 5mm tubes in the baseline systems induces heat pump performance degradation; by optimizing the 5 mm tube heat pumps with added tube rows, the system refrigerant charge is reduced up to 33% compared with the baseline; the optimized low-GWP 5 mm tube heat pumps offer the same or higher performance under both cooling and heating mode; that under cooling mode, the EER improvement is up to 10.7% and under heating mode the COP improvement is up to 3.4%; and a smart flow control device to maintain counter-flow circuitry pattern on both operating modes can improve the heating performance of 5 mm tube optimized system by up to 3.0%. In an effort to better understand the environmental impacts of these systems, life cycle climate performance (LCCP) evaluation method is used to assess the baseline and optimized systems. LCCP considers the direct and indirect emissions of the system over the course of its lifetime from manufacturing to disposal. Our analyses indicate that the optimized systems using 5mm tubes and low-GWP refrigerants can reduce life-cycle CO 2 emission significantly. And improving system efficiency is the most effective way to reduce the emission of low-GWP refrigerant systems. This report shows that using 5 mm diameter tubes in heat exchangers is a feasible approach to develop heat pumps with low-GWP refrigerants. Using the proposed design approach can yield higher system efficiency with lower environmental impact.

42 ENGINEERING↗
DOE OSTI2024

Characterization of Mn 5 Ge 3 Contacts on a Shallow Ge/SiGe Heterostructure

Mn 5 Ge 3 is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of Mn 5 Ge 3 -based contacts on a Ge/SiGe quantum well heterostructure via solid-state synthesis. X-ray diffraction spectra fitting indicates the formation of Mn 5 Ge 3 -based contacts on bulk Ge and Ge/SiGe. High-resolution scanning transmission electron microscopy imaging and energy dispersive X-ray spectroscopy verify the correct Mn 5 Ge 3 -based phase formation. Schottky diode measurements, transmission line measurements, and Hall measurements reveal that Mn 5 Ge 3 -based contacts serve as good p-type contacts for Ge/SiGe quantum well heterostructures due to having a low Schottky barrier height of 0.10 eV (extracted from a Mn 5 Ge 3 /n-Ge analogue) and a contact resistance in the order of 1 kΩ. Furthermore, we show that these electrical characteristics have a gate-voltage dependence, thereby providing tunability.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The Importance of Solution Studies for the Structural Characterization of the Enterovirus 5’ Cloverleaf

Enteroviruses initiate genomic replication via a highly conserved mechanism that is controlled by an RNA platform, also known as the 5’ cloverleaf (5’CL). Here, we present a biophysical analysis of the 5’CL conformation of three enterovirus serotypes under various ionic conditions, utilizing CD spectroscopy, size-exclusion chromatography, and small-angle X-ray scattering. In general, a tendency toward a smaller monomeric hydrodynamic radius in the presence of salts was observed, but the exact structural signature of each 5’CL varied depending upon the serotype. Rhinovirus B14 (RVB14) exhibited at least two monomeric conformations and a low propensity for dimerization, while poliovirus 1 (PV1) showed a high propensity for dimerization, which was enhanced by the presence of salts. Enterovirus D70 was observed to be somewhat intermediate, with primarily a monomeric structure, but possessing some potential for dimerization. The equilibrium between the two monomeric and the dimeric conformations is also discussed. These results indicate that the 5’CL conformation may be more complex than the current literature suggests, thus underscoring the need for a combined crystal and solution approach for the accurate representation of the 5’CL conformation, and the conformation of other RNA structural elements, under native conditions.

Virology↗
DOE OSTI2020

Materials Data on Ba3Sr5Co3(CuO4)5 by Materials Project

Ba3Sr5Co3(CuO4)5 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twelve inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.75–3.10 Å. In the second Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.71–2.93 Å. In the third Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.72–2.92 Å. In the fourth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.74–2.93 Å. In the fifth Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.71–3.03 Å. In the sixth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.69–2.98 Å. In the seventh Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.71–3.01 Å. In the eighth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.73–2.92 Å. In the ninth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.72–2.96 Å. In the tenth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.71–2.95 Å. In the eleventh Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.74–2.95 Å. In the twelfth Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.68–3.20 Å. There are twenty inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.53–3.22 Å. In the second Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.57–2.95 Å. In the third Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–3.03 Å. In the fourth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.51–3.10 Å. In the fifth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–3.00 Å. In the sixth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–2.99 Å. In the seventh Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.53–3.08 Å. In the eighth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–3.25 Å. In the ninth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–2.90 Å. In the tenth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.50–3.04 Å. In the eleventh Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–3.07 Å. In the twelfth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.54–3.05 Å. In the thirteenth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.50–3.07 Å. In the fourteenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–3.16 Å. In the fifteenth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.53–3.01 Å. In the sixteenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.54–3.23 Å. In the seventeenth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–3.06 Å. In the eighteenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.58–3.26 Å. In the nineteenth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.53–2.87 Å. In the twentieth Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.53–3.05 Å. There are twelve inequivalent Co4+ sites. In the first Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, corners with two CoO5 square pyramids, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 2–4°. There are a spread of Co–O bond distances ranging from 1.83–2.35 Å. In the second Co4+ site, Co4+ is bonded to five O2- atoms to form distorted CoO5 square pyramids that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, corners with two CoO5 square pyramids, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 3–8°. There are a spread of Co–O bond distances ranging from 1.82–2.27 Å. In the third Co4+ site, Co4+ is bonded to five O2- atoms to form distorted CoO5 square pyramids that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, corners with two CoO5 square pyramids, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 4–7°. There are a spread of Co–O bond distances ranging from 1.83–2.20 Å. In the fourth Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CuO6 octahedra, corners with three CoO6 octahedra, and a cornercorner with one CuO4 tetrahedra. The corner-sharing octahedra tilt angles range from 3–7°. There are a spread of Co–O bond distances ranging from 1.88–2.19 Å. In the fifth Co4+ site, Co4+ is bonded to five O2- atoms to form distorted CoO5 square pyramids that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, corners with two CoO5 square pyramids, and a cornercorner with one CuO4 tetrahedra. The corner-sharing octahedra tilt angles range from 3–10°. There are a spread of Co–O bond distances ranging from 1.83–2.19 Å. In the sixth Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CuO6 octahedra, corners with three CoO6 octahedra, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 2–8°. There are a spread of Co–O bond distances ranging from 1.86–2.28 Å. In the seventh Co4+ site, Co4+ is bonded to five O2- atoms to form distorted CoO5 square pyramids that share a cornercorner with one CoO6 octahedra, corners with three CoO5 square pyramids, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedral tilt angles are 8°. There are a spread of Co–O bond distances ranging from 1.83–2.15 Å. In the eighth Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two CoO6 octahedra, corners with two CuO6 octahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 5–6°. There are a spread of Co–O bond distances ranging from 1.87–2.19 Å. In the ninth Co4+ site, Co4+ is bonded to five O2- atoms to form CoO5 square pyramids that share a cornercorner with one CoO6 octahedra, corners with three CoO5 square pyramids, and a cornercorner with one CuO4 tetrahedra. The corner-sharing octahedral tilt angles are 6°. There are a spread of Co–O bond distances ranging from 1.83–2.15 Å. In the tenth Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two CoO6 octahedra, corners with two CuO6 octahedra, and corners with two CuO4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 5–8°. There are a spread of Co–O bond distances ranging from 1.86–2.19 Å. In the eleventh Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CoO6 octahedra, corners with three CoO5 square pyramids, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedral tilt angles are 4°. There are a spread of Co–O bond distances ranging from 1.80–2.38 Å. In the twelfth Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two CoO6 octahedra, corners with two CuO6 octahedra, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 2–7°. There are a spread of Co–O bond distances ranging from 1.88–2.31 Å. There are twenty inequivalent Cu+2.40+ sites. In the first Cu+2.40+ site, Cu+2.40+ is bonded to six O2- atoms to form CuO6 octahedra that share a cornercorner with one CuO6 octahedra, corners with three CoO6 octahedra, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 5–8°. There are a spread of Cu–O bond distances ranging from 1.96–2.36 Å. In the second Cu+2.40+ site, Cu+2.40+ is bonded to six O2- atoms to form CuO6 octahedra that share a cornercorner with one CuO6 octahedra, corners with three CoO6 octahedra, and corners with two CuO4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 2–7°. There are a spread of Cu–O bond distances ranging from 2.01–2.14 Å. In the third Cu+2.40+ site, Cu+2.40+ is bonded to six O2- atoms to form distorted CuO6 octahedra that share a cornercorner with one CoO6 octahedra, corners with three CoO5 square pyramids, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedral tilt angles are 2°. There are a spread of Cu–O bond distances ranging from 1.95–2.60 Å. In the fourth Cu+2.40+ site, Cu+2.40+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with two CoO6 octahedra, corners with two CuO6 octahedra, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 2–5°. There are a spread of Cu–O bond distances ranging from 1.96–2.32 Å. In the fifth Cu+2.40+ site, Cu+2.40+ is bonded to four O2- atoms to form CuO4 trigonal pyramids that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 12–21°. There are a spread of Cu–O bond distances ranging from 1.84–1.91 Å. In the sixth Cu+2.40+ site, Cu+2.40+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with two CuO6 octahedra, a cornercorner with one CuO4 tetrahedra, and a cornercorner with one CuO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 18–21°. There are a spread of Cu–O bond distances ranging from 1.84–1.92 Å. In the seventh Cu+2.40+

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca8Al3(FeO4)5 by Materials Project

Ca8Al3(FeO4)5 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eight inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.85 Å. In the second Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.32–2.92 Å. In the third Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.35–2.84 Å. In the fourth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.32–2.91 Å. In the fifth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.33–2.87 Å. In the sixth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.97 Å. In the seventh Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.98 Å. In the eighth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.86 Å. There are five inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four AlO6 octahedra and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 11–12°. There are a spread of Fe–O bond distances ranging from 1.98–2.15 Å. In the second Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one FeO6 octahedra, a cornercorner with one AlO6 octahedra, and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–38°. There are a spread of Fe–O bond distances ranging from 1.87–1.96 Å. In the third Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with two AlO6 octahedra and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–34°. There are a spread of Fe–O bond distances ranging from 1.88–1.96 Å. In the fourth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one FeO6 octahedra, a cornercorner with one AlO6 octahedra, and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–38°. There are a spread of Fe–O bond distances ranging from 1.86–1.96 Å. In the fifth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with two AlO6 octahedra and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–34°. There are a spread of Fe–O bond distances ranging from 1.88–1.96 Å. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with two equivalent AlO6 octahedra, and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 10–12°. There are a spread of Al–O bond distances ranging from 1.90–2.06 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with two equivalent AlO6 octahedra, and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 10–12°. There are a spread of Al–O bond distances ranging from 1.88–2.07 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four AlO6 octahedra and corners with two FeO4 tetrahedra. The corner-sharing octahedral tilt angles are 10°. There are a spread of Al–O bond distances ranging from 1.90–2.05 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+, one Fe3+, and one Al3+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+, one Fe3+, and one Al3+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+, one Fe3+, and one Al3+ atom. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+, one Fe3+, and one Al3+ atom. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+, one Fe3+, and one Al3+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and two Fe3+ atoms. In the seventh O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+, one Fe3+, and one Al3+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and two Fe3+ atoms. In the ninth O2- site, O2- is bonded to four Ca2+ and two Al3+ atoms to form distorted OCa4Al2 octahedra that share a cornercorner with one OCa4Al2 octahedra, corners with four OCa2Fe2 tetrahedra, an edgeedge with one OCa4Al2 octahedra, and faces with three OCa4Al2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the tenth O2- site, O2- is bonded in a 6-coordinate geometry to four Ca2+, one Fe3+, and one Al3+ atom. In the eleventh O2- site, O2- is bonded in a 6-coordinate geometry to four Ca2+, one Fe3+, and one Al3+ atom. In the twelfth O2- site, O2- is bonded to four Ca2+ and two Al3+ atoms to form distorted OCa4Al2 octahedra that share a cornercorner with one OCa4Al2 octahedra, corners with four OCa2Fe2 tetrahedra, an edgeedge with one OCa4Al2 octahedra, and faces with three OCa4Al2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the thirteenth O2- site, O2- is bonded to four Ca2+ and two Al3+ atoms to form distorted OCa4Al2 octahedra that share a cornercorner with one OCa4Al2 octahedra, corners with four OCa2Fe2 tetrahedra, an edgeedge with one OCa4Al2 octahedra, and faces with three OCa4Al2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the fourteenth O2- site, O2- is bonded in a 6-coordinate geometry to four Ca2+, one Fe3+, and one Al3+ atom. In the fifteenth O2- site, O2- is bonded in a 6-coordinate geometry to four Ca2+, one Fe3+, and one Al3+ atom. In the sixteenth O2- site, O2- is bonded to four Ca2+ and two Al3+ atoms to form distorted OCa4Al2 octahedra that share a cornercorner with one OCa4Al2 octahedra, corners with four OCa2Fe2 tetrahedra, an edgeedge with one OCa4Al2 octahedra, and faces with three OCa4Al2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the seventeenth O2- site, O2- is bonded to two Ca2+ and two Fe3+ atoms to form distorted OCa2Fe2 tetrahedra that share corners with six OCa4Al2 octahedra and corners with two OCa2Fe2 tetrahedra. The corner-sharing octahedra tilt angles range from 24–77°. In the eighteenth O2- site, O2- is bonded to two Ca2+ and two Fe3+ atoms to form distorted OCa2Fe2 tetrahedra that share corners with two OCa4Al2 octahedra and corners with two OCa2Fe2 tetrahedra. The corner-sharing octahedra tilt angles range from 23–62°. In the nineteenth O2- site, O2- is bonded to two Ca2+ and two Fe3+ atoms to form distorted OCa2Fe2 tetrahedra that share corners with six OCa4Al2 octahedra and corners with two OCa2Fe2 tetrahedra. The corner-sharing octahedra tilt angles range from 23–77°. In the twentieth O2- site, O2- is bonded to two Ca2+ and two Fe3+ atoms to form distorted OCa2Fe2 tetrahedra that share corners with two OCa4Al2 octahedra and corners with two OCa2Fe2 tetrahedra. The corner-sharing octahedra tilt angles range from 48–77°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na26(Ge3Au8)5 by Materials Project

Na26(Au8Ge3)5 is alpha-derived structured and crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are eleven inequivalent Na sites. In the first Na site, Na is bonded in a 12-coordinate geometry to three Na, nine Au, and three Ge atoms. There are a spread of Na–Na bond distances ranging from 3.06–3.56 Å. There are a spread of Na–Au bond distances ranging from 3.10–3.36 Å. There are a spread of Na–Ge bond distances ranging from 3.27–3.35 Å. In the second Na site, Na is bonded in a 12-coordinate geometry to two Na, nine Au, and three Ge atoms. The Na–Na bond length is 3.46 Å. There are a spread of Na–Au bond distances ranging from 3.09–3.38 Å. There are a spread of Na–Ge bond distances ranging from 3.27–3.38 Å. In the third Na site, Na is bonded in a 10-coordinate geometry to two equivalent Na, ten Au, and three Ge atoms. Both Na–Na bond lengths are 3.06 Å. There are a spread of Na–Au bond distances ranging from 3.10–3.21 Å. There are a spread of Na–Ge bond distances ranging from 3.19–3.27 Å. In the fourth Na site, Na is bonded in a 4-coordinate geometry to nine Au and four Ge atoms. There are a spread of Na–Au bond distances ranging from 3.08–3.27 Å. There are two shorter (3.11 Å) and two longer (3.27 Å) Na–Ge bond lengths. In the fifth Na site, Na is bonded in a 11-coordinate geometry to two equivalent Na, eight Au, and five Ge atoms. Both Na–Na bond lengths are 3.16 Å. There are four shorter (3.10 Å) and four longer (3.17 Å) Na–Au bond lengths. There are a spread of Na–Ge bond distances ranging from 3.10–3.18 Å. In the sixth Na site, Na is bonded in a 11-coordinate geometry to two Na, ten Au, and three Ge atoms. Both Na–Na bond lengths are 3.00 Å. There are a spread of Na–Au bond distances ranging from 3.10–3.33 Å. There are one shorter (3.18 Å) and two longer (3.41 Å) Na–Ge bond lengths. In the seventh Na site, Na is bonded in a 5-coordinate geometry to four Na, nine Au, and three Ge atoms. The Na–Na bond length is 3.31 Å. There are a spread of Na–Au bond distances ranging from 3.13–3.53 Å. There are one shorter (3.26 Å) and two longer (3.35 Å) Na–Ge bond lengths. In the eighth Na site, Na is bonded in a 5-coordinate geometry to one Na, nine Au, and two equivalent Ge atoms. There are a spread of Na–Au bond distances ranging from 3.13–3.50 Å. Both Na–Ge bond lengths are 3.41 Å. In the ninth Na site, Na is bonded in a 5-coordinate geometry to four Na, eight Au, and four Ge atoms. The Na–Na bond length is 3.49 Å. There are a spread of Na–Au bond distances ranging from 3.10–3.49 Å. There are a spread of Na–Ge bond distances ranging from 3.25–3.58 Å. In the tenth Na site, Na is bonded in a 5-coordinate geometry to one Na, seven Au, and three Ge atoms. There are a spread of Na–Au bond distances ranging from 3.08–3.28 Å. There are one shorter (3.27 Å) and two longer (3.37 Å) Na–Ge bond lengths. In the eleventh Na site, Na is bonded in a 7-coordinate geometry to seven Au and three Ge atoms. There are a spread of Na–Au bond distances ranging from 3.09–3.25 Å. There are one shorter (3.36 Å) and two longer (3.37 Å) Na–Ge bond lengths. There are fourteen inequivalent Au sites. In the first Au site, Au is bonded in a 12-coordinate geometry to five Na, one Au, and one Ge atom. The Au–Au bond length is 2.87 Å. The Au–Ge bond length is 2.55 Å. In the second Au site, Au is bonded in a 12-coordinate geometry to five Na, one Au, and one Ge atom. The Au–Au bond length is 2.88 Å. The Au–Ge bond length is 2.56 Å. In the third Au site, Au is bonded in a 1-coordinate geometry to five Na, one Au, and one Ge atom. The Au–Au bond length is 2.88 Å. The Au–Ge bond length is 2.53 Å. In the fourth Au site, Au is bonded in a 12-coordinate geometry to five Na, one Au, and one Ge atom. The Au–Au bond length is 2.90 Å. The Au–Ge bond length is 2.55 Å. In the fifth Au site, Au is bonded in a 1-coordinate geometry to five Na, one Au, and one Ge atom. The Au–Au bond length is 2.92 Å. The Au–Ge bond length is 2.55 Å. In the sixth Au site, Au is bonded to twelve Au atoms to form AuAu12 cuboctahedra that share corners with two equivalent GeNa6Au6 cuboctahedra. In the seventh Au site, Au is bonded in a 12-coordinate geometry to six Na, three Au, and three Ge atoms. There are one shorter (2.82 Å) and two longer (2.89 Å) Au–Au bond lengths. There are a spread of Au–Ge bond distances ranging from 2.61–2.96 Å. In the eighth Au site, Au is bonded in a 12-coordinate geometry to six Na, four Au, and two Ge atoms. There are a spread of Au–Au bond distances ranging from 2.82–3.09 Å. There are one shorter (2.59 Å) and one longer (2.82 Å) Au–Ge bond lengths. In the ninth Au site, Au is bonded in a 12-coordinate geometry to six Na, three Au, and three Ge atoms. There are one shorter (2.90 Å) and one longer (2.91 Å) Au–Au bond lengths. There are a spread of Au–Ge bond distances ranging from 2.59–2.90 Å. In the tenth Au site, Au is bonded in a 12-coordinate geometry to six Na, three Au, and three Ge atoms. There are one shorter (2.91 Å) and one longer (2.95 Å) Au–Au bond lengths. There are a spread of Au–Ge bond distances ranging from 2.60–2.88 Å. In the eleventh Au site, Au is bonded in a 12-coordinate geometry to six Na, four Au, and two Ge atoms. There are one shorter (2.90 Å) and one longer (3.02 Å) Au–Au bond lengths. There are one shorter (2.55 Å) and one longer (2.68 Å) Au–Ge bond lengths. In the twelfth Au site, Au is bonded in a 12-coordinate geometry to six Na, four Au, and two Ge atoms. The Au–Au bond length is 3.08 Å. There are one shorter (2.56 Å) and one longer (2.64 Å) Au–Ge bond lengths. In the thirteenth Au site, Au is bonded in a 3-coordinate geometry to seven Na, five Au, and two Ge atoms. The Au–Au bond length is 2.75 Å. There are one shorter (3.16 Å) and one longer (3.21 Å) Au–Ge bond lengths. In the fourteenth Au site, Au is bonded in a 1-coordinate geometry to seven Na, four equivalent Au, and one Ge atom. The Au–Ge bond length is 2.49 Å. There are seven inequivalent Ge sites. In the first Ge site, Ge is bonded in a 11-coordinate geometry to six Na and five Au atoms. In the second Ge site, Ge is bonded in a 12-coordinate geometry to five Na and five Au atoms. In the third Ge site, Ge is bonded in a 11-coordinate geometry to six Na and five Au atoms. In the fourth Ge site, Ge is bonded in a 12-coordinate geometry to six Na and six Au atoms. In the fifth Ge site, Ge is bonded to six Na and six Au atoms to form distorted GeNa6Au6 cuboctahedra that share a cornercorner with one AuAu12 cuboctahedra and an edgeedge with one GeNa6Au6 cuboctahedra. In the sixth Ge site, Ge is bonded in a 1-coordinate geometry to seven Na and five Au atoms. In the seventh Ge site, Ge is bonded in a 12-coordinate geometry to three Na, four Au, and one Ge atom. The Ge–Ge bond length is 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Indium segregation in Gd 5 (Si, Ge) 4 magnetocaloric materials

Chemical substitution is one of the most efficient tools to tune and optimize magnetic and magnetocaloric properties of the giant magnetocaloric materials. In particular, Indium substitutions could be useful both for tuning properties of these interesting intermetallic materials and to unveil their local-scale behavior across the magnetostructural transition via hyperfine techniques. Hence, in order to investigate the effect of Indium additions on the crystal structure, micro-structure, magnetic and magnetocaloric properties, a series of In-containing samples derived from the base Gd 5 Si 1.2 Ge 2.8 stoichiometry were prepared. Here, the major findings are that while In is insoluble in the 5:4 phase, it will instead promote the emergence of the impurity 5:3 phase and segregates into this phase. Hence, In leads to major crystallographic changes, which enhance atomic disorder and disrupt the Si to Ge ratio in the 5:4 phase. Subsequently, a higher 5:4 unit cell volume and a lower magnetic ordering temperature are found in the In-substituted samples. Finally, the magnetocaloric properties of the In-substituted samples reveal a detrimental effect on the maximum magnetic entropy change.

36 MATERIALS SCIENCE↗