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Platinized tin oxide catalysts for CO2 lasers - Effects of pretreatment

Platinized tin oxide surfaces used for low-temperature CO oxidation in CO2 lasers have been characterized before and after reduction in CO at 125 and 250 C using ion scattering spectroscopy (ISS) and X-ray photoelectron spectroscopy (XPS). XPS indicates that the Pt is present initially as Pto2. Reduction at 125 C converts the PtO2 to Pt(OH)2 while reduction at 250 C converts the PtO2 to metallic Pt. ISS shows that the Pt in the outermost atomic layer of the catalyst is mostly covered by substrate species during the 250 C reduction. Both the ISS and XPS results are consistent with Pt/Sn alloy formation. The surface dehydration and migration of substrate species over surface Pt and Sn appear to explain why a CO pretreatment at 250 C produces inferior CO oxidation activities compared to a 125 C pretreatment.

Gardner, Steven D.↗

How Deep and Hot was Earth's Magma Ocean? Combined Experimental Datasets for the Metal-silicate Partitioning of 11 Siderophile Elements - Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd

Since approximately 1990 high pressure and temperature (PT) experiments on metal-silicate systems have showed that partition coefficients (D) for siderophile (iron-loving) elements are much different than those measured at low PT conditions. The high PT data have been used to argue for a magma ocean during growth of the early Earth. Initial conclusions were based on experiments and calculations for a small number of elements such as Ni and Co. However, for many elements only a limited number of experimental data were available then, and they only hinted at values of metal-silicate D's at high PT conditions. In the ensuing decades there have been hundreds of new experiments carried out and published on a wide range of siderophile elements. At the same time several different models have been advanced to explain the siderophile elements in the earth's mantle: a) intermediate depth magma ocean; 25-30 GPa, b) deep magma ocean; up to 50 GPa, and c) early reduced and later oxidized magma ocean. Some studies have drawn conclusions based on a small subset of siderophile elements, or a set of elements that provides little leverage on the big picture (like slightly siderophile elements), and no single study has attempted to quantitatively explain more than 5 elements at a time. The purpose of this abstract is to update the predictive expressions outlined by Righter et al. (1997) with new experimental data from the last decade, test the predictive ability of these expressions against independent datasets (there are more data now to do this properly), and to apply the resulting expressions to the siderophile element patterns in Earth's upper mantle. The predictive expressions have the form: lnD = alnfO2 + b/T + cP/T + d(1Xs) + e(1Xc) + SigmafiXi + g These expressions are guided by the thermodynamics of simple metal-oxide equilibria that control each element, include terms that mimic the activity coefficients of each element in the metal and silicate, and quantify the effect of variable oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and approximately 2200 K, and show that D(Pd) and D(Cu) become too low at the PT conditions of the deepest models. Furthermore, models which force fit V and Cr mantle concentrations by metal-silicate equilibrium overlook the fact that at early Earth mantle fO2, these elements will be more compatible in Mg-perovskite and (Fe,Mg)O than in metal. Thus an intermediate depth magma ocean, at 25-30 GPa, 2200 K, and at IW-2, can explain more mantle siderophile element concentrations than other models.

Righter, Kevin↗

Highly Siderophile Elements as Tracers for the Subcontinental Mantle Evolution Beneath the Southwestern USA: The San Carlos and Kilbourne Hole Peridotite Xenoliths Revisited

Peridotite xenoliths from San Carlos, Arizona, and Kilbourne Hole, New Mexico, have been studied since the 1970 s to give insights into melting and metasomatism in the subcontinental mantle beneath the southwestern USA. More recently, the highly siderophile elements (HSE; Os, Ir, Ru, Rh, Pt, Pd, and Re) and the included Re-Os isotope system have been established as powerful tools for the study of mantle processes because of their range in compatibility during mantle melting and their siderophile and chalcophile geochemical behavior. Model aluminachron Re-Os ages for San Carlos and Kilbourne Hole, as well as for the nearby Dish Hill and Vulcan's Throne sites, give consistent depletion ages of around 2.2 Ga. This age can be interpreted as a single large scale mantle melting event linked to crustal formation and continental growth under the southwestern USA. Highly siderophile elements, however, may be added to depleted peridotites via melt-rock interaction, especially the more incompatible and hence mobile Pt, Pd, and Re. This may result in overprinting of the signature of melt extraction, thus abating the usefulness of Re-Os mantle extraction model ages. A comprehensive characterization of the suite of mantle xenoliths from the SW USA in terms of HSE concentrations is thus necessary to re-assess the Re-Os system for dating purposes. San Carlos peridotites are depleted to moderately fertile, as indicated by their bulk Al2O3 contents between 0.66 wt% and 3.13 wt%. Bulk Os-187/Os-188 in San Carlos peridotites range from 0.1206 to 0.1357. In contrast, Kilbourne Hole peridotites tend to be more fertile with Al2O3 between 2.11 and 3.78 wt%, excluding one extremely depleted sample with 0.30 wt% Al2O3, and have Os-187/Os-188 between 0.1156 and 0.1272, typical for mantle peridotites. No large fractionation between the more compatible HSE Os, Ir, and Ru are observed. The more incompatible HSE Re, Pd, and to a minor extent, Pt, however, are depleted in a number of samples by factors of up to 4 for Pt, 6 for Pd, and 20 for Re, compared to primitive mantle estimates. This is in agreement with previous studies from the same locales, which demonstrated the presence of different populations of mantle xenoliths having undergone various degrees of melt extraction. The depletion of the more incompatible elements (Re, Pd, and Pt) also suggests that the HSE budgets of the SW USA peridotites were primarily established by extraction of basaltic melt, and reflect only minor influence from later episodes of metasomatism. Model Re-Os ages obtained from San Carlos and Kilbourne Hole xenoliths may thus reflect ages of crustal formation and mantle depletion in the SW USA region.

vanAcken, D.↗

Monitoring Location and Angular Orientation of a Pill

A mobile pill transmitter system moves through, or adjacent to, one or more organs in an animal or human body, while transmitting signals from its present location and/or present angular orientation. The system also provides signals from which the present roll angle of the pill, about a selected axis, can be determined. When the location coordinates angular orientation and the roll angle of the pill are within selected ranges, an aperture on the pill container releases a selected chemical into, or onto, the body. Optionally, the pill, as it moves, provides a sequence of visually perceptible images. The times for image formation may correspond to times at which the pill transmitter system location or image satisfies one of at least four criteria. This invention provides and supplies an algorithm for exact determination of location coordinates and angular orientation coordinates for a mobile pill transmitter (PT), or other similar device that is introduced into, and moves within, a GI tract of a human or animal body. A set of as many as eight nonlinear equations has been developed and applied, relating propagation of a wireless signal between either two, three, or more transmitting antennas located on the PT, to four or more non-coplanar receiving antennas located on a signal receiver appliance worn by the user. The equations are solved exactly, without approximations or iterations, and are applied in several environments: (1) association of a visual image, transmitted by the PT at each of a second sequence of times, with a PT location and PT angular orientation at that time; (2) determination of a position within the body at which a drug or chemical substance or other treatment is to be delivered to a selected portion of the body; (3) monitoring, after delivery, of the effect(s) of administration of the treatment; and (4) determination of one or more positions within the body where provision and examination of a finer-scale image is warranted.

Schipper, John F.↗

Development and Test of High Temperature Surface Acoustic Wave Gas Sensors

The demand for sensors in hostile environments, such as power plant environments, aerospace environments, oil and gas extraction, and high-temperature metallurgy environments, has risen over the past decades in a continuous attempt to increase process control, improve energy and process efficiency in production, reduce operational and maintenance costs, increase safety, and perform condition-based maintenance in equipment and structures operating in high-temperature harsh-environment conditions. The increased reliability, improved performance, and development of new sensors and networks with a multitude of components, especially wireless networks, are the target for operation in harsh environments. Gas sensors, in particular H2 sensors, operating above 200 C are required in the instrumentation, process control and general safety of a number of industries including coal, natural gas, and nuclear power generation facilities, the aerospace and automotive industries, metallurgical production and defense-related applications. The surface acoustic wave (SAW) platform is a particularly promising option for high-temperature, harsh-environment gas sensing applications since the platform exhibits advantages, such as battery-free and wireless operation, small size, possibility for scale production using well-developed technologies from the semiconductor industry, and low cost of installation and operation. In this work, one-port SAW resonators (SAWRs) operating along five different orientations on a commercially available langasite (LGS) wafer employing Pt-Al2O3 electrodes and reflectors were designed, fabricated, and used as high-temperature H2 sensors. Two of the selected orientations were predicted and confirmed to have temperature-compensated operation above 150 C. A gas sensor test setup was developed, capable of gas cycling between N2, O2 and N2/H2 mixtures under extended high-temperature periods (up to 650 C for over 20 hours). Thin film Pt-Al2O3 was used as the electrode material for the transducers and reflectors capable of high-temperature operation, and also as H2 sensing film. In addition, yttria-stabilized zirconia (YSZ) thin films with Pt decoration were tested as sensing films aimed to enhance the SAWR sensor response to H2. The SAW devices were monitored in excess of 1700 hours in real-time during gas cycling sequences up to 600 C, leading to the following findings: i) the Pt-Al2O3 electrodes performed better for H2 sensing than the Pt-decorated YSZ sensing film, showing as much as 50% higher frequency variation response in the 200 C to 400 C range; ii) different crystallographic orientations operating on the same LGS wafer experienced different responses to H2 exposures up to 500 C; iii) the surface oxidation state of the SAWR sensors was shown to have an important impact on subsequent H2 exposure responses. In addition, a sensor system employing two LGS SAWRs, aligned along two different orientations, has been developed to simultaneously determine H2 presence and temperature. Finally, wireless interrogation of a SAWR sensor was successful within the gas cycling test fixture, and successful wireless H2 detection was achieved above 400 C.

Ayes Moncada, Armando↗

Assessing the Role of the Support in Acetic Acid Hydrodeoxygenation Selectivity on Pt/TiO2

To produce drop-in quality biofuels following the thermochemical conversion of biomass via catalytic fast pyrolysis (CFP), hydrodeoxygenation (HDO) reactions can be performed to remove excess oxygen and create a more stable bio-oil product. HDO reactions involve co-feeding the CFP vapor-phase product and H2 gas over bi-functional catalysts, such as noble-metal catalysts supported on reducible metal oxides (e.g., Pt/TiO2). Recent model-compound studies, focusing on important classes of species in the CFP vapor mixture, have sought to determine the role of the various Pt/TiO2 actives sites (i.e., Pt-metal, TiO2-support, Pt-TiO2-interfacial sites) in producing the observed desired deoxygenation and undesired decarboxylation/decarbonylation products. One important class of compounds in the CFP vapor-phase product is carboxylic acids (e.g., acetic acid). Prior experimental work on acetic acid HDO (AA-HDO) found that Pt/C and Pt/TiO2 catalysts favored the formation of undesired C-C and desired C-O bond-dissociation products; however, the fundamental surface chemistry driving this shift in selectivity has not been established. This presentation employs atomic-scale modeling to determine, through comparisons of adsorption and reaction energetics, how Pt-metal, Pt-TiO2-interface, and interfacial-vacancy sites catalyze the competing reaction pathways for AA-HDO. Our analysis indicates that hydroxyl vacancies at the Pt-TiO2 interface are critical for lowering barriers for C-O bond-cleavage steps, such that they become favorable/competitive with respect to C-C bond-dissociation steps.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗

Durability of PGM catalyst MEAs of polymer electrolyte membrane fuel cells for heavy-duty vehicles

Polymer electrolyte membrane fuel cells (PEMFCs) are promising power sources for heavy-duty vehicles (HDVs) owing to cleanliness and efficiency. However, the degradation of membrane electrode assemblies (MEAs) under HDV conditions remains a huge challenge. Here, this work investigated MEA durability under HDV conditions using a US Department of Energy standard accelerated stress test for 180,000 cycles (equivalent to 1 million miles of HDV operation). Effects of catalyst Pt content on MEA durability were examined using homemade 30% Pt/C (H-Pt/C) and commercial 46% Pt/C (C-Pt/C) catalysts. Both MEAs experienced H 2 /air and H 2 /O 2 performance loss over cycles. Analysis with scanning transmission electron microscopy, X-ray diffraction, inductively coupled plasma mass spectrometry, and mercury intrusion porosimetry revealed severe degradation of Pt nanoparticles (NPs), support structures, and the catalyst layer. Two degradation stages for NPs were proposed: Ostwald ripening dominated the initial 60,000 cycles, followed by combined Ostwald ripening and particle migration. Measurements with ion chromatography, high-frequency resistance, and oxygen-diffusion resistance revealed degradation of membrane and ionomer, respectively.

25 ENERGY STORAGE↗

Electrochemical Evolution of Fuel Cell Platinum Nanocatalysts on Carbon Nanotubes at the Atomic Scale

The evolution of Pt nanoparticles supported on carbon nanotubes is analyzed before and after electrochemical potential cycling, using identical location aberration-corrected transmission electron microscopy, for applications in proton exchange membrane fuel cells. The work is focused on the half-cell accelerated stress test protocol of potential cycles ranging between 1.0 and 1.5 V RHE to represent the start-up/shutdown settings of a fuel cell vehicle. The research work reveals that particle migration and coalescence are key mechanisms for a reduction in the Pt nanoparticle surface area at the early stages of potential cycling. Further, the mechanism for particle movement and coalescence is attributed to carbon corrosion, catalyzed either by Pt or by bulk corrosion of the carbon nanotubes. Carbon corrosion results in the appearance of carbon vacancies at the carbon nanotube/Pt nanoparticle interface during cycling, as well as the formation of edge and surface defects. During cycling, the concentration of the dissoluble Pt increases. As soon as a significant amount is reached, subnanometer/atomic clusters emerge on the carbon nanotube support, which can move and coalesce, or redeposit on the surface of larger particles through Ostwald ripening.

25 ENERGY STORAGE↗

Fe–N–C Boosts the Stability of Supported Platinum Nanoparticles for Fuel Cells

The poor durability of Pt-based nanoparticles dispersed on carbon black is the challenge for the application of long-life polymer electrolyte fuel cells. Recent work suggests that Fe- and N-codoped carbon (Fe-N-C) might be a better support than conventional high-surface-area carbon. In this work, we find that the electrochemical surface area retention of Pt/Fe-N-C is much better than that of commercial Pt/C during potential cycling in both acidic and basic media. In situ inductively coupled plasma mass spectrometry studies indicate that the Pt dissolution rate of Pt/Fe-N-C is 3 times smaller than that of Pt/C during cycling. Density functional theory calculations further illustrate that the Fe-N-C substrate can provide strong and stable support to the Pt nanoparticles and alleviate the oxide formation by adjusting the electronic structure. The strong metal-substrate interaction, together with a lower metal dissolution rate and highly stable support, may be the reason for the significantly enhanced stability of Pt/Fe-N-C. In conclusion, this finding highlights the importance of carbon support selection to achieve a more durable Pt-based electrocatalyst for fuel cells.

25 ENERGY STORAGE↗

Spontaneous and explicit parity-time-symmetry breaking in drift-wave instabilities

A method of parity-time- (PT) symmetry analysis is introduced to study the high-dimensional, complicated parameter space of drift-wave instabilities. Here, we show that spontaneous PT-symmetry breaking leads to the ion temperature gradient instability of drift waves, and the collisional instability is the result of explicit PT-symmetry breaking. A new unstable drift wave induced by finite collisionality is identified. It is also found that gradients of ion temperature and density can destabilize the ion cyclotron waves when PT symmetry is explicitly broken by a finite collisionality.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Performance and Durability of Hybrid Fuel Cell Systems for Class-8 Long Haul Trucks

Hybrid fuel cell-battery configurations are investigated that overcome thermal management issues in fuel cell powertrains for heavy-duty Class 8 trucks. The battery is sized so that it has sufficient capacity to provide supplemental power and energy on a hill climb transient at end-of-life. A dynamic load sharing strategy is developed to distribute the power demand between the fuel cell system (FCS) and the energy storage system in a manner that optimizes their lifetimes. The FCS end-of-life is identified as the terminal point beyond which the stack cannot generate the rated power with target power density at 0.7 V and 40 °C ambient temperature. Reaching the target lifetime with a-Pt/C cathode catalyst in one hybrid configuration requires voltage clipping to 813 mV, idle power limited to 50 kW, catalyst overloading to 0.45 mg cm -2 total Pt in anode and cathode, and 44% active membrane area oversizing. The stack and FCS drive cycle efficiencies decrease by 4.2% and 5.4%, respectively, during the electrode lifetime. Further, the FCS performance, durability and cost are compared with the targets of 68% peak efficiency, 0.30 mg cm -2 total Pt loading, 2.5 kW/g PGM Pt group metal (PGM) loading, 750 mW cm -2 power density, 25,000-h lifetime and $80/kW cost.

33 ADVANCED PROPULSION SYSTEMS↗

Materials Data on Cs2PtC2(OF)4 by Materials Project

Cs2PtC2(OF)4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded to four O2- and eight F1- atoms to form distorted CsO4F8 cuboctahedra that share corners with two equivalent CsO4F8 cuboctahedra, a cornercorner with one PtO2F4 octahedra, faces with two equivalent CsO4F8 cuboctahedra, and faces with three PtO2F4 octahedra. The corner-sharing octahedral tilt angles are 17°. There are a spread of Cs–O bond distances ranging from 3.25–3.36 Å. There are a spread of Cs–F bond distances ranging from 3.13–3.28 Å. In the second Cs1+ site, Cs1+ is bonded in a 11-coordinate geometry to four O2- and seven F1- atoms. There are a spread of Cs–O bond distances ranging from 3.19–3.41 Å. There are a spread of Cs–F bond distances ranging from 3.11–3.29 Å. In the third Cs1+ site, Cs1+ is bonded to four O2- and eight F1- atoms to form distorted CsO4F8 cuboctahedra that share corners with two equivalent CsO4F8 cuboctahedra, a cornercorner with one PtO2F4 octahedra, faces with two equivalent CsO4F8 cuboctahedra, and faces with three PtO2F4 octahedra. The corner-sharing octahedral tilt angles are 16°. There are a spread of Cs–O bond distances ranging from 3.19–3.32 Å. There are a spread of Cs–F bond distances ranging from 3.16–3.33 Å. In the fourth Cs1+ site, Cs1+ is bonded in a 11-coordinate geometry to four O2- and seven F1- atoms. There are a spread of Cs–O bond distances ranging from 3.22–3.44 Å. There are a spread of Cs–F bond distances ranging from 3.12–3.32 Å. There are two inequivalent Pt2+ sites. In the first Pt2+ site, Pt2+ is bonded to two O2- and four F1- atoms to form PtO2F4 octahedra that share a cornercorner with one CsO4F8 cuboctahedra and faces with three CsO4F8 cuboctahedra. Both Pt–O bond lengths are 2.01 Å. There are a spread of Pt–F bond distances ranging from 1.97–2.01 Å. In the second Pt2+ site, Pt2+ is bonded to two O2- and four F1- atoms to form PtO2F4 octahedra that share a cornercorner with one CsO4F8 cuboctahedra and faces with three CsO4F8 cuboctahedra. There are one shorter (2.01 Å) and one longer (2.02 Å) Pt–O bond lengths. There are a spread of Pt–F bond distances ranging from 1.97–2.01 Å. There are four inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.32 Å) C–O bond length. In the second C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.22 Å) and one longer (1.33 Å) C–O bond length. In the third C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.32 Å) C–O bond length. In the fourth C4+ site, C4+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.22 Å) and one longer (1.33 Å) C–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Cs1+, one Pt2+, and one C4+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to two Cs1+ and one C4+ atom. In the third O2- site, O2- is bonded in a distorted water-like geometry to two Cs1+, one Pt2+, and one C4+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Cs1+, one Pt2+, and one C4+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to two Cs1+ and one C4+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to two Cs1+ and one C4+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Cs1+, one Pt2+, and one C4+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to two Cs1+ and one C4+ atom. There are eight inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to four Cs1+ and one Pt2+ atom. In the second F1- site, F1- is bonded in a distorted single-bond geometry to four Cs1+ and one Pt2+ atom. In the third F1- site, F1- is bonded in a distorted single-bond geometry to four Cs1+ and one Pt2+ atom. In the fourth F1- site, F1- is bonded in a distorted single-bond geometry to four Cs1+ and one Pt2+ atom. In the fifth F1- site, F1- is bonded in a distorted single-bond geometry to three Cs1+ and one Pt2+ atom. In the sixth F1- site, F1- is bonded in a distorted single-bond geometry to four Cs1+ and one Pt2+ atom. In the seventh F1- site, F1- is bonded in a distorted single-bond geometry to three Cs1+ and one Pt2+ atom. In the eighth F1- site, F1- is bonded in a distorted single-bond geometry to four Cs1+ and one Pt2+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Al3Pt2 by Materials Project

Al3Pt2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Pt is bonded in a body-centered cubic geometry to eight Al atoms. There are a spread of Pt–Al bond distances ranging from 2.51–2.72 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 6-coordinate geometry to six equivalent Pt atoms. In the second Al site, Al is bonded in a 5-coordinate geometry to five equivalent Pt atoms.

36 MATERIALS SCIENCE↗

Materials Data on Tb2Al6Si4Pt by Materials Project

Tb2PtAl6Si4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Tb is bonded to six Si atoms to form TbSi6 octahedra that share corners with twelve AlSi4 tetrahedra, edges with six equivalent TbSi6 octahedra, and edges with six AlSi4 tetrahedra. There are three shorter (2.95 Å) and three longer (2.98 Å) Tb–Si bond lengths. Pt is bonded in a body-centered cubic geometry to eight Al atoms. There are six shorter (2.54 Å) and two longer (2.55 Å) Pt–Al bond lengths. There are three inequivalent Al sites. In the first Al site, Al is bonded to one Pt and three equivalent Si atoms to form AlSi3Pt tetrahedra that share corners with three equivalent TbSi6 octahedra, corners with ten AlSiPt3 tetrahedra, edges with three equivalent TbSi6 octahedra, and edges with three equivalent AlSiPt3 tetrahedra. The corner-sharing octahedral tilt angles are 15°. All Al–Si bond lengths are 2.56 Å. In the second Al site, Al is bonded to four equivalent Si atoms to form distorted AlSi4 tetrahedra that share corners with six equivalent TbSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent TbSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–54°. There are three shorter (2.50 Å) and one longer (2.54 Å) Al–Si bond lengths. In the third Al site, Al is bonded to three equivalent Pt and one Si atom to form distorted AlSiPt3 tetrahedra that share corners with three equivalent TbSi6 octahedra, corners with twelve AlSiPt3 tetrahedra, and edges with six AlSiPt3 tetrahedra. The corner-sharing octahedral tilt angles are 55°. The Al–Si bond length is 2.62 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded to three equivalent Tb and four Al atoms to form a mixture of distorted edge and corner-sharing SiTb3Al4 pentagonal bipyramids. In the second Si site, Si is bonded to three equivalent Tb and four equivalent Al atoms to form a mixture of distorted edge and corner-sharing SiTb3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗

Materials Data on ScPPt by Materials Project

ScPtP crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Sc3+ is bonded in a 11-coordinate geometry to six equivalent Pt2- and five equivalent P1- atoms. There are a spread of Sc–Pt bond distances ranging from 2.96–3.11 Å. There are a spread of Sc–P bond distances ranging from 2.69–2.84 Å. Pt2- is bonded in a 12-coordinate geometry to six equivalent Sc3+, two equivalent Pt2-, and four equivalent P1- atoms. Both Pt–Pt bond lengths are 2.95 Å. There are a spread of Pt–P bond distances ranging from 2.42–2.75 Å. P1- is bonded in a 9-coordinate geometry to five equivalent Sc3+ and four equivalent Pt2- atoms.

36 MATERIALS SCIENCE↗

Materials Data on FeNiPt2 by Materials Project

Pt2FeNi crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Fe2+ is bonded in a body-centered cubic geometry to eight equivalent Pt2- atoms. All Fe–Pt bond lengths are 2.67 Å. Pt2- is bonded to four equivalent Fe2+, four equivalent Pt2-, and four equivalent Ni2+ atoms to form a mixture of distorted face, edge, and corner-sharing PtFe4Ni4Pt4 cuboctahedra. All Pt–Pt bond lengths are 2.74 Å. All Pt–Ni bond lengths are 2.67 Å. Ni2+ is bonded in a body-centered cubic geometry to eight equivalent Pt2- atoms.

36 MATERIALS SCIENCE↗

Materials Data on Sr(As3Pt2)2 by Materials Project

Sr(Pt2As3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Sr2+ is bonded to six Pt2- atoms to form distorted corner-sharing SrPt6 pentagonal pyramids. There are a spread of Sr–Pt bond distances ranging from 2.99–3.18 Å. There are three inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded to six As1+ atoms to form corner-sharing PtAs6 octahedra. The corner-sharing octahedra tilt angles range from 60–65°. There are two shorter (2.52 Å) and four longer (2.53 Å) Pt–As bond lengths. In the second Pt2- site, Pt2- is bonded to two equivalent Sr2+ and four As1+ atoms to form PtSr2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four PtSr2As4 octahedra. The corner-sharing octahedra tilt angles range from 20–108°. There are a spread of Pt–As bond distances ranging from 2.48–2.54 Å. In the third Pt2- site, Pt2- is bonded to two equivalent Sr2+ and four As1+ atoms to form PtSr2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four equivalent PtSr2As4 octahedra. The corner-sharing octahedra tilt angles range from 30–83°. There are two shorter (2.47 Å) and two longer (2.53 Å) Pt–As bond lengths. There are three inequivalent As1+ sites. In the first As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms. In the second As1+ site, As1+ is bonded in a trigonal planar geometry to three Pt2- atoms. In the third As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms.

36 MATERIALS SCIENCE↗

Materials Data on Ba(As3Pt2)2 by Materials Project

Ba(Pt2As3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ba2+ is bonded to six Pt2- atoms to form distorted corner-sharing BaPt6 pentagonal pyramids. There are a spread of Ba–Pt bond distances ranging from 3.01–3.23 Å. There are three inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded to six As1+ atoms to form corner-sharing PtAs6 octahedra. The corner-sharing octahedra tilt angles range from 59–65°. There are four shorter (2.54 Å) and two longer (2.56 Å) Pt–As bond lengths. In the second Pt2- site, Pt2- is bonded to two equivalent Ba2+ and four As1+ atoms to form PtBa2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four PtBa2As4 octahedra. The corner-sharing octahedra tilt angles range from 22–109°. There are a spread of Pt–As bond distances ranging from 2.49–2.56 Å. In the third Pt2- site, Pt2- is bonded to two equivalent Ba2+ and four As1+ atoms to form PtBa2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four equivalent PtBa2As4 octahedra. The corner-sharing octahedra tilt angles range from 33–82°. There are two shorter (2.48 Å) and two longer (2.54 Å) Pt–As bond lengths. There are three inequivalent As1+ sites. In the first As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms. In the second As1+ site, As1+ is bonded in a trigonal planar geometry to three Pt2- atoms. In the third As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms.

36 MATERIALS SCIENCE↗