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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Fe3Pt by Materials Project

Fe3Pt crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are five inequivalent Fe sites. In the first Fe site, Fe is bonded to nine Fe and three equivalent Pt atoms to form distorted FeFe9Pt3 cuboctahedra that share corners with twelve equivalent FeFe9Pt3 cuboctahedra, edges with six equivalent PtFe6Pt6 cuboctahedra, edges with eighteen FeFe9Pt3 cuboctahedra, faces with six equivalent PtFe6Pt6 cuboctahedra, and faces with twelve FeFe9Pt3 cuboctahedra. There are three shorter (2.50 Å) and six longer (2.72 Å) Fe–Fe bond lengths. All Fe–Pt bond lengths are 2.69 Å. In the second Fe site, Fe is bonded to twelve Fe atoms to form FeFe12 cuboctahedra that share corners with six equivalent FeFe12 cuboctahedra, corners with six equivalent PtFe6Pt6 cuboctahedra, edges with six equivalent PtFe6Pt6 cuboctahedra, edges with eighteen FeFe9Pt3 cuboctahedra, and faces with eighteen FeFe9Pt3 cuboctahedra. All Fe–Fe bond lengths are 2.72 Å. In the third Fe site, Fe is bonded to nine Fe and three equivalent Pt atoms to form distorted FeFe9Pt3 cuboctahedra that share corners with seventeen FeFe9Pt3 cuboctahedra, edges with six equivalent PtFe6Pt6 cuboctahedra, edges with sixteen FeFe9Pt3 cuboctahedra, faces with six equivalent PtFe6Pt6 cuboctahedra, and faces with fifteen FeFe9Pt3 cuboctahedra. There are three shorter (2.50 Å) and six longer (2.72 Å) Fe–Fe bond lengths. All Fe–Pt bond lengths are 2.69 Å. In the fourth Fe site, Fe is bonded to sixteen Fe atoms to form FeFe16 cuboctahedra that share corners with six equivalent PtFe6Pt6 cuboctahedra, corners with sixteen FeFe9Pt3 cuboctahedra, edges with six equivalent PtFe6Pt6 cuboctahedra, edges with eighteen FeFe9Pt3 cuboctahedra, and faces with thirty-four FeFe9Pt3 cuboctahedra. There are a spread of Fe–Fe bond distances ranging from 2.50–5.45 Å. In the fifth Fe site, Fe is bonded to nine Fe and three equivalent Pt atoms to form distorted FeFe9Pt3 cuboctahedra that share corners with seventeen FeFe9Pt3 cuboctahedra, edges with six equivalent PtFe6Pt6 cuboctahedra, edges with sixteen FeFe9Pt3 cuboctahedra, faces with six equivalent PtFe6Pt6 cuboctahedra, and faces with fifteen FeFe9Pt3 cuboctahedra. All Fe–Fe bond lengths are 2.72 Å. All Fe–Pt bond lengths are 2.69 Å. Pt is bonded to six equivalent Fe and six equivalent Pt atoms to form distorted PtFe6Pt6 cuboctahedra that share corners with six equivalent FeFe12 cuboctahedra, corners with six equivalent PtFe6Pt6 cuboctahedra, edges with six equivalent PtFe6Pt6 cuboctahedra, edges with eighteen FeFe9Pt3 cuboctahedra, faces with six equivalent PtFe6Pt6 cuboctahedra, and faces with twelve equivalent FeFe9Pt3 cuboctahedra. All Pt–Pt bond lengths are 2.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Probing the Behavior of Composition‐Tunable Ultrathin PtNi Nanowires for CO Oxidation and Small‐Molecule Electrocatalytic Reactions

We have successfully synthesized ultrathin nanowires of pure Pt, Pt 99 Ni 1 , Pt 9 Ni 1 , and Pt 7 Ni 3 using a modified room-temperature soft-template method. Analysis of both methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) results found that the Pt 7 Ni 3 samples yielded the best performance with specific activities of 0.36 and 0.34 mA/cm 2 respectively. Additionally, formic acid oxidation reaction (FAOR) tests noted that both Pt and PtNi nanowires oxidize small organic molecules (SOMs) via an indirect pathway. CO oxidation data suggests little measurable performance without any pre-reduction treatment; however, after annealing in H 2 , we detected significantly improved CO 2 formation for both Pt 9 Ni 1 and Pt 7 Ni 3 motifs. These observations highlight the importance of pre-treating these nanowires under a reducing atmosphere to enhance their performance for CO oxidation. To explain these findings, we collected extended x-ray adsorption fine structure (EXAFS) spectroscopy data, consistent with the presence of partial alloying with a tendency for Pt and Ni to segregate, thereby implying the formation of a Pt-rich shell coupled with a Ni-rich core. Here, we also observed that the degree of alloying within the nanowires increased after annealing in a reducing atmosphere, a finding deduced through analysis of the coordination numbers and calculations of Cowley's short range order parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Improving intrinsic oxygen reduction activity and stability: Atomic layer deposition preparation of platinum-titanium alloy catalysts

Improved activity and stability Pt-based catalysts for the oxygen reduction reaction (ORR) are needed to perpetuate the deployment of polymer electrolyte fuel cells (PEFCs) in the transportation sector. In this study, we use atomic layer deposition of TiO 2 and Pt coupled with thermal reductive annealing to prepare Pt 3 Ti electrocatalysts. The atomic level synthetic control resulted in Pt 3 Ti nanoparticles with high ORR performance, including a mass activity of 1.84 A/mg Pt and excellent electrochemical stability. The Pt 3 Ti nanoparticles show excellent specific activity — 5.3-fold higher than commercial Pt/C and 3-fold higher than polycrystalline Pt, exceeding the performance of any PtTi catalysts reported to date. Combined experimental and computational efforts indicate that Pt enrichment on the Pt 3 Ti enhances the activity, and the intrinsic stability of the Pt 3 Ti phase provides durability. Subsequently, this knowledge, along with the facile fabrication of alloys by atomic layer deposition, can be leveraged to designed improved performance catalysts.

25 ENERGY STORAGE↗
DOE OSTI2025

Characterizing the surface compositions of supported bimetallic PtSn clusters: Effects of cluster-support interactions and surface adsorbates

PtSn bimetallic clusters on TiO2(110) and highly oriented pyrolytic graphite (HOPG) surfaces have been characterized by scanning tunneling microscopy, low energy ion scattering (LEIS), Xray photoelectron spectroscopy, and temperature programmed desorption (TPD); density functional theory (DFT) calculations have also been performed to better understand adsorption of CO and D2 on the PtSn surfaces. On TiO2 at coverages of 2 ML of Pt and 2 ML of Sn, exclusively bimetallic clusters are formed for both orders of deposition because clusters of the first metal completely cover the surface such that all atoms of the second metal are incorporated into the existing clusters. In contrast, on HOPG, the high mobility and weak cluster-support interactions on HOPG result in much larger 2 ML monometallic clusters (~30 Å high) that do not completely cover the surface, and deposition of the second metal produces larger clusters as well as smaller ones. Despite the difference in cluster morphologies for the different orders of deposition and supports, the LEIS experiments demonstrate that in all cases, the PtSn clusters are rich in Sn at the surface, as expected based on the lower surface free energy for Sn compared to Pt. Furthermore, the +0.2 eV shift in the Sn(3d5/2) binding energy observed on all surfaces in the presence of Pt is consistent with PtSn alloy formation. Deposition of 2 ML of Sn on TiO2 produces two-dimensional clusters with oxidation of Sn and reduction of titania at the clustersupport interface, but addition of Pt to the Sn clusters causes Sn to diffuse away from this interface, leaving Sn in the metallic state. TPD experiments on 2 ML Pt/TiO2 with increasing coverages of Sn show that the number of adsorption sites for D2 sharply decreases to nearly zero at 0.5 ML, while CO adsorption decreases to zero only at much higher Sn coverages of 2 ML. DFT studies for Sn modified Pt surfaces and bulk structures demonstrate that for CO adsorption at low Sn coverages (<0.25 ML), the strong Pt-CO interactions induce diffusion of Pt to the cluster surface and the formation of a bulk Pt3Sn alloy, whereas D2 adsorption does not lead to interactions with the Pt surface that are strong enough to induce alloy formation. A single Sn adatom prevents D2 adsorption on four neighboring Pt atoms via site-blocking and the donation of electron density to Pt.

Li, Fangliang↗
DOE OSTI2023

Toward Quantum Chemical Free Energy Simulations of Platinum Nanoparticles on Titania Support

Platinum nanoparticles (Pt-NPs) supported on titania surfaces are costly but indispensable heterogeneous catalysts because of their highly effective and selective catalytic properties. Therefore, it is vital to understand their physicochemical processes during catalysis to optimize their use and to further develop better catalysts. However, simulating these dynamic processes is challenging due to the need for a reliable quantum chemical method to describe chemical bond breaking and bond formation during the processes but, at the same time, fast enough to sample a large number of configurations required to compute the corresponding free energy surfaces. Density functional theory (DFT) is often used to explore Pt-NPs; nonetheless, it is usually limited to some minimum-energy reaction pathways on static potential energy surfaces because of its high computational cost. In this work, we report a combination of the density functional tight binding (DFTB) method as a fast but reliable approximation to DFT, the steered molecular dynamics (SMD) technique, and the Jarzynski equality to construct free energy surfaces of the temperature-dependent diffusion and growth of platinum particles on a titania surface. In particular, we present the parametrization for Pt-X (X = Pt, Ti, or O) interactions in the framework of the second-order DFTB method, using a previous parametrization for titania as a basis. The optimized parameter set was used to simulate the surface diffusion of a single platinum atom (Pt 1 ) and the growth of Pt 6 from Pt 5 and Pt 1 on the rutile (110) surface at three different temperatures (T = 400, 600, 800 K). The free energy profile was constructed by using over a hundred SMD trajectories for each process. We found that increasing the temperature has a minimal effect on the formation free energy; nevertheless, it significantly reduces the free energy barrier of Pt atom migration on the TiO 2 surface and the transition state (TS) of its deposition. In a concluding remark, the methodology opens the pathway to quantum chemical free energy simulations of Pt-NPs’ temperature-dependent growth and other transformation processes on the titania support.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Photosynthesis of a Photocatalyst: Single Atom Platinum Captured and Stabilized by an Iron(III) Engineered Defect

Single atom (SA), noble metal catalysts are of interest due to high projected catalytic activity while minimizing cost. Common issues facing many synthesis methodologies include complicated processes, low yields of SA product, and production of mixtures of SA and nanoparticles (NPs). Herein we report a simple, room-temperature synthesis of single Pt-atom decorated, anatase Fe-doped TiO 2 particles that leverages the Fe dopant as an engineered defect site to photodeposit and stabilize atomically dispersed Pt. Both particle morphology and Fe dopant location are based on thermodynamic principles (Gibbs-Wulff construction). CO-DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) reveals absence of bridge-bonded CO signal, confirming atomically dispersed Pt. XAS (x-ray absorption spectroscopy) of both Pt and Fe indicates Fe-O-Pt bonding that persists through catalytic cycling. Mass balance indicates Pt loading on single particles is 2.5 wt% Pt; single Pt-atom decorated nanoparticle yield is 17%. Pt containing particles show more than an order-of-magnitude increased photo-oxidation efficiency relative to particles containing only Fe. High single-atom-Pt yield, ease of synthesis, and high catalytic activity demonstrate the utility and promise of this method. In conclusion, the principles of this photodeposition synthesis allow for its generalizability towards other SA metals of catalytic interest.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Density Functional Tight Binding Insights into Plasmonic Silver–Platinum Nanoparticles and Alloys for Enhanced Photocatalysis

Developing accurate and efficient Slater-Koster (SK) tight-binding parameter sets is essential for quantum plasmonic studies of alloyed metal nanoparticles, as conventional time dependent density functional theory (TD-DFT) calculations are computationally prohibitive for larger clusters. In this work, we develop and validate density functional tight binding (DFTB) parameter sets for both ground state (GS-SK) and excited state (ES-SK) calculations to study the structural, electronic, and optical properties of silver (Ag), platinum (Pt), and Ag–Pt nanoalloys. Our investigation of the ground state properties demonstrates that the GS-SK parameters enable DFTB to closely reproduce the electronic structures of platinum clusters with diverse sizes and geometries – showing qualitative agreement with DFT for density of states (DOS) profiles and energy levels. The ES-SK parameters accurately describe excited-state properties compared to TD-DFT reference calculations, including the broad, featureless absorption profiles of Pt that are dominated by interband transitions. Using the ES-SK parameters within a real-time TD-DFTB framework, we compute size-dependent optical absorption spectra of Ag, Pt and Ag-Pt nanocubes containing up to 1099 atoms (size ∼4.18 nm). A detailed study of Ag–Pt and Pt-Ag core–shell nanoparticles shows quenching of the Ag plasmon resonance even at monolayer coverage for Ag-Pt, but not for Pt-Ag. We also show how to define submonolayer Ag-core Pt-shell cubic structures that have similar optical properties to those generated experimentally for much larger particles, which offers potential for describing plasmon-enhanced photocatalysis. Collectively, the GS-SK and ES-SK parameter sets provide an accurate, computationally efficient approach for modeling the complex optical and electronic behavior of noble–transition metal nanostructures and their alloys.

SPR↗
NASA NTRS2006

Advanced Catalysts for Fuel Cells

This viewgraph presentation reviews the development of catalyst for Fuel Cells. The objectives of the project are to reduce the cost of stack components and reduce the amount of precious metal used in fuel cell construction. A rapid combinatorial screening technique based on multi-electrode thin film array has been developed and validated for identifying catalysts for oxygen reduction; focus shifted from methanol oxidation in FY05 to oxygen reduction in FY06. Multi-electrode arrays of thin film catalysts of Pt-Ni and Pt-Ni-Zr have been deposited. Pt-Ni and have been characterized electrochemically and structurally. Pt-Ni-Zr and Pt-Ni films show higher current density and onset potential compared to Pt. Electrocatalytic activity and onset potential are found to be strong function of the lattice constant. Thin film Pt(59)Ni(39)Zr(2) can provide 10 times the current density of thin film Pt. Thin film Pt(59)Ni(39)Zr(2) also shows 65mV higher onset potential than Pt.

fuel cells↗
DOE OSTI2020

Materials Data on HfPt3 by Materials Project

HfPt3 is Uranium Silicide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded to twelve Pt atoms to form a mixture of face and corner-sharing HfPt12 cuboctahedra. There are six shorter (2.86 Å) and six longer (2.87 Å) Hf–Pt bond lengths. In the second Hf site, Hf is bonded to twelve Pt atoms to form a mixture of face and corner-sharing HfPt12 cuboctahedra. All Hf–Pt bond lengths are 2.86 Å. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a distorted see-saw-like geometry to four Hf atoms. In the second Pt site, Pt is bonded in a distorted square co-planar geometry to four Hf atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si5Pt12 by Materials Project

Pt12Si5 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. there are two inequivalent Pt+1.67- sites. In the first Pt+1.67- site, Pt+1.67- is bonded in a 12-coordinate geometry to four Si4+ atoms. There are a spread of Pt–Si bond distances ranging from 2.42–2.85 Å. In the second Pt+1.67- site, Pt+1.67- is bonded in a 2-coordinate geometry to four equivalent Si4+ atoms. There are a spread of Pt–Si bond distances ranging from 2.43–2.86 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded in a 10-coordinate geometry to ten Pt+1.67- atoms. In the second Si4+ site, Si4+ is bonded in a body-centered cubic geometry to eight equivalent Pt+1.67- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrMgPt by Materials Project

MgPrPt crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Mg is bonded in a 4-coordinate geometry to four Pt atoms. There are two shorter (2.77 Å) and two longer (2.96 Å) Mg–Pt bond lengths. Pr is bonded in a 5-coordinate geometry to five Pt atoms. There are four shorter (3.10 Å) and one longer (3.14 Å) Pr–Pt bond lengths. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 9-coordinate geometry to six equivalent Mg and three equivalent Pr atoms. In the second Pt site, Pt is bonded in a 9-coordinate geometry to three equivalent Mg and six equivalent Pr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmMgPt by Materials Project

MgSmPt crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Mg is bonded in a 4-coordinate geometry to four Pt atoms. There are two shorter (2.75 Å) and two longer (2.90 Å) Mg–Pt bond lengths. Sm is bonded in a 5-coordinate geometry to five Pt atoms. There are four shorter (3.07 Å) and one longer (3.08 Å) Sm–Pt bond lengths. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 9-coordinate geometry to six equivalent Mg and three equivalent Sm atoms. In the second Pt site, Pt is bonded in a 9-coordinate geometry to three equivalent Mg and six equivalent Sm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ErGe2Pt by Materials Project

ErPtGe2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Er sites. In the first Er site, Er is bonded in a 12-coordinate geometry to six equivalent Pt and eight Ge atoms. There are four shorter (3.20 Å) and two longer (3.33 Å) Er–Pt bond lengths. There are six shorter (3.00 Å) and two longer (3.07 Å) Er–Ge bond lengths. In the second Er site, Er is bonded in a 12-coordinate geometry to four equivalent Pt and ten Ge atoms. All Er–Pt bond lengths are 3.25 Å. There are a spread of Er–Ge bond distances ranging from 3.23–3.46 Å. Pt is bonded in a 10-coordinate geometry to five Er and five Ge atoms. There are a spread of Pt–Ge bond distances ranging from 2.49–2.65 Å. There are three inequivalent Ge sites. In the first Ge site, Ge is bonded in a 8-coordinate geometry to four Er, three equivalent Pt, and one Ge atom. The Ge–Ge bond length is 2.62 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to six Er, two equivalent Pt, and one Ge atom. The Ge–Ge bond length is 2.43 Å. In the third Ge site, Ge is bonded in a 2-coordinate geometry to four equivalent Er, two equivalent Pt, and one Ge atom. The Ge–Ge bond length is 2.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Pt by Materials Project

Mg3Pt crystallizes in the hexagonal P6_3cm space group. The structure is three-dimensional. there are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a distorted trigonal non-coplanar geometry to three equivalent Pt atoms. All Mg–Pt bond lengths are 2.67 Å. In the second Mg site, Mg is bonded in a trigonal planar geometry to three equivalent Pt atoms. All Mg–Pt bond lengths are 2.70 Å. In the third Mg site, Mg is bonded in a distorted trigonal planar geometry to three equivalent Pt atoms. There are one shorter (2.79 Å) and two longer (2.84 Å) Mg–Pt bond lengths. In the fourth Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Pt atoms. There are one shorter (2.78 Å) and one longer (2.79 Å) Mg–Pt bond lengths. Pt is bonded in a 10-coordinate geometry to eight Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(PtO2)3 by Materials Project

CoPt3O6 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Co2+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (2.19 Å) and four longer (2.41 Å) Co–O bond lengths. There are two inequivalent Pt+3.33+ sites. In the first Pt+3.33+ site, Pt+3.33+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Pt–O bond lengths are 1.99 Å. In the second Pt+3.33+ site, Pt+3.33+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing PtO6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are four shorter (2.05 Å) and two longer (2.06 Å) Pt–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Co2+ and three Pt+3.33+ atoms to form a mixture of distorted edge and corner-sharing OCoPt3 tetrahedra. In the second O2- site, O2- is bonded to two equivalent Co2+ and two equivalent Pt+3.33+ atoms to form a mixture of edge and corner-sharing OCo2Pt2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeMgPt by Materials Project

MgCePt crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Mg is bonded in a 4-coordinate geometry to four Pt atoms. There are two shorter (2.74 Å) and two longer (2.92 Å) Mg–Pt bond lengths. Ce is bonded in a 5-coordinate geometry to five Pt atoms. There are four shorter (3.06 Å) and one longer (3.12 Å) Ce–Pt bond lengths. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 9-coordinate geometry to three equivalent Mg and six equivalent Ce atoms. In the second Pt site, Pt is bonded in a 9-coordinate geometry to six equivalent Mg and three equivalent Ce atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbGe2Pt by Materials Project

TbPtGe2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Tb sites. In the first Tb site, Tb is bonded in a 12-coordinate geometry to six equivalent Pt and eight Ge atoms. There are four shorter (3.22 Å) and two longer (3.30 Å) Tb–Pt bond lengths. There are a spread of Tb–Ge bond distances ranging from 3.02–3.07 Å. In the second Tb site, Tb is bonded in a 12-coordinate geometry to four equivalent Pt and ten Ge atoms. All Tb–Pt bond lengths are 3.28 Å. There are a spread of Tb–Ge bond distances ranging from 3.26–3.44 Å. Pt is bonded in a 10-coordinate geometry to five Tb and five Ge atoms. There are a spread of Pt–Ge bond distances ranging from 2.50–2.66 Å. There are three inequivalent Ge sites. In the first Ge site, Ge is bonded in a 8-coordinate geometry to four Tb, three equivalent Pt, and one Ge atom. The Ge–Ge bond length is 2.63 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to six Tb, two equivalent Pt, and one Ge atom. The Ge–Ge bond length is 2.44 Å. In the third Ge site, Ge is bonded in a 2-coordinate geometry to four equivalent Tb, two equivalent Pt, and one Ge atom. The Ge–Ge bond length is 2.43 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te4Pt3 by Materials Project

Pt3Te4 crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two Pt3Te4 ribbons oriented in the (0, 1, 0) direction. there are two inequivalent Pt+2.67+ sites. In the first Pt+2.67+ site, Pt+2.67+ is bonded in a T-shaped geometry to three Te2- atoms. There are two shorter (2.69 Å) and one longer (2.74 Å) Pt–Te bond lengths. In the second Pt+2.67+ site, Pt+2.67+ is bonded in a linear geometry to two equivalent Te2- atoms. Both Pt–Te bond lengths are 2.58 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 2-coordinate geometry to two equivalent Pt+2.67+ atoms. In the second Te2- site, Te2- is bonded in a 5-coordinate geometry to two Pt+2.67+ atoms.

36 MATERIALS SCIENCE↗