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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Boosting Thermoelectric Performance in Nanocrystalline Ternary Skutterudite Thin Films through Metallic CoTe 2 Integration

Metal–semiconductor nanocomposites have emerged as a viable strategy for concurrently tailoring both thermal and electronic transport properties of established thermoelectric materials, ultimately achieving synergistic performance. In this investigation, a series of nanocomposite thin films were synthesized, embedding metallic cobalt telluride (CoTe 2 ) nanophase within the nanocrystalline ternary skutterudite (Co(Ge 1.22 Sb 0.22 )Te 1.58 or CGST) matrix. Our approach harnessed composition fluctuation-induced phase separation and in situ growth during thermal annealing to seamlessly integrate the metallic phase. The distinctive band structures of both materials have developed an ohmic-type contact characteristic at the interface, which raised carrier density considerably yet negligibly affected the mobility counterpart, leading to a substantial improvement in electrical conductivity. The intricate balance in transport properties is further influenced by the metallic CoTe 2 phase’s role in diminishing lattice thermal conductivity. The presence of the metallic phase instigates enhanced phonon scattering at the interface boundaries. Consequently, a 2-fold enhancement in the thermoelectric figure of merit (zT ~ 1.30) is attained with CGST-7 wt. % CoTe 2 nanocomposite film at 655 K compared to that of pristine CGST.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta(CoTe)2 by Materials Project

Ta(CoTe)2 crystallizes in the orthorhombic Pnma space group. The structure is two-dimensional and consists of two Ta(CoTe)2 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Ta sites. In the first Ta site, Ta is bonded in a 10-coordinate geometry to eight Co and two equivalent Te atoms. There are four shorter (2.56 Å) and four longer (2.84 Å) Ta–Co bond lengths. Both Ta–Te bond lengths are 2.87 Å. In the second Ta site, Ta is bonded in a 11-coordinate geometry to eight Co and three Te atoms. There are four shorter (2.64 Å) and four longer (2.71 Å) Ta–Co bond lengths. There are one shorter (2.82 Å) and two longer (3.02 Å) Ta–Te bond lengths. There are four inequivalent Co sites. In the first Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are a spread of Co–Co bond distances ranging from 2.56–2.86 Å. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the second Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.60 Å) and one longer (2.84 Å) Co–Co bond lengths. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the third Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.56 Å) and one longer (2.60 Å) Co–Co bond lengths. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. In the fourth Co site, Co is bonded in a 10-coordinate geometry to four Ta, three Co, and three Te atoms. There are one shorter (2.64 Å) and one longer (2.71 Å) Co–Ta bond lengths. The Co–Co bond length is 2.86 Å. There are a spread of Co–Te bond distances ranging from 2.54–2.62 Å. There are three inequivalent Te sites. In the first Te site, Te is bonded in a 5-coordinate geometry to one Ta and four Co atoms. In the second Te site, Te is bonded in a 6-coordinate geometry to two Ta, two Co, and two equivalent Te atoms. There are one shorter (3.25 Å) and one longer (3.33 Å) Te–Te bond lengths. In the third Te site, Te is bonded in a 4-coordinate geometry to four Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe by Materials Project

CoTe is Tungsten Carbide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Co2+ is bonded to six equivalent Te2- atoms to form a mixture of edge, corner, and face-sharing CoTe6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Co–Te bond lengths are 2.62 Å. Te2- is bonded in a 6-coordinate geometry to six equivalent Co2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y5(CoTe)2 by Materials Project

Y5(CoTe)2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent Y sites. In the first Y site, Y is bonded in a 7-coordinate geometry to three Co and four equivalent Te atoms. There are one shorter (2.83 Å) and two longer (2.84 Å) Y–Co bond lengths. There are two shorter (3.33 Å) and two longer (3.35 Å) Y–Te bond lengths. In the second Y site, Y is bonded in a 6-coordinate geometry to three Co and three equivalent Te atoms. There are two shorter (2.85 Å) and one longer (2.92 Å) Y–Co bond lengths. There are one shorter (3.15 Å) and two longer (3.20 Å) Y–Te bond lengths. In the third Y site, Y is bonded in a distorted square co-planar geometry to two Co and two equivalent Te atoms. There are one shorter (2.95 Å) and one longer (3.26 Å) Y–Co bond lengths. Both Y–Te bond lengths are 3.18 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to seven Y and two equivalent Co atoms. Both Co–Co bond lengths are 2.38 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to seven Y and two equivalent Co atoms. Te is bonded in a 8-coordinate geometry to eight Y atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

CoTe 2 : A Quantum Critical Dirac Metal with Strong Spin Fluctuations

Abstract Quantum critical points separating weak ferromagnetic and paramagnetic phases trigger many novel phenomena. Dynamical spin fluctuations not only suppress the long‐range order, but can also lead to unusual transport and even superconductivity. Combining quantum criticality with topological electronic properties presents a rare and unique opportunity. Here, by means of ab initio calculations and magnetic, thermal, and transport measurements, it is shown that the orthorhombic CoTe 2 is close to ferromagnetism, which appears suppressed by spin fluctuations. Calculations and transport measurements reveal nodal Dirac lines, making it a rare combination of proximity to quantum criticality and Dirac topology.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er5(CoTe)2 by Materials Project

Er5Co2Te2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent Er sites. In the first Er site, Er is bonded in a distorted square co-planar geometry to two Co and two equivalent Te atoms. There are one shorter (2.90 Å) and one longer (3.18 Å) Er–Co bond lengths. Both Er–Te bond lengths are 3.17 Å. In the second Er site, Er is bonded in a 6-coordinate geometry to three Co and three equivalent Te atoms. There are two shorter (2.79 Å) and one longer (2.90 Å) Er–Co bond lengths. There are one shorter (3.13 Å) and two longer (3.19 Å) Er–Te bond lengths. In the third Er site, Er is bonded in a 7-coordinate geometry to three Co and four equivalent Te atoms. There are two shorter (2.79 Å) and one longer (2.81 Å) Er–Co bond lengths. There are two shorter (3.32 Å) and two longer (3.36 Å) Er–Te bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to seven Er and two equivalent Co atoms. Both Co–Co bond lengths are 2.40 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to seven Er and two equivalent Co atoms. Te is bonded in a 8-coordinate geometry to eight Er atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe(PbO3)2 by Materials Project

Pb2CoTeO6 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six equivalent TeO6 octahedra. The corner-sharing octahedra tilt angles range from 14–18°. There are four shorter (2.13 Å) and two longer (2.14 Å) Co–O bond lengths. Pb2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Pb–O bond distances ranging from 2.61–3.16 Å. Te4+ is bonded to six O2- atoms to form TeO6 octahedra that share corners with six equivalent CoO6 octahedra. The corner-sharing octahedra tilt angles range from 14–18°. There is two shorter (1.95 Å) and four longer (1.96 Å) Te–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Co4+, four equivalent Pb2+, and one Te4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Co4+, four equivalent Pb2+, and one Te4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe(PbO3)2 by Materials Project

Pb2CoTeO6 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Co4+ is bonded to six equivalent O2- atoms to form CoO6 octahedra that share corners with six equivalent TeO6 octahedra. The corner-sharing octahedral tilt angles are 17°. All Co–O bond lengths are 2.14 Å. Pb2+ is bonded in a 12-coordinate geometry to nine equivalent O2- atoms. There are a spread of Pb–O bond distances ranging from 2.58–2.93 Å. Te4+ is bonded to six equivalent O2- atoms to form TeO6 octahedra that share corners with six equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 17°. All Te–O bond lengths are 1.96 Å. O2- is bonded in a 2-coordinate geometry to one Co4+, three equivalent Pb2+, and one Te4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTe(PbO3)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2025

Energizing Robust Sulfur/Lithium Electrochemistry via Nanoscale-Asymmetric-Size Synergism

Sluggish redox kinetics and dendrite growth perplex the fulfillment of efficient electrochemistry in lithium–sulfur (Li–S) batteries. The complicated sulfur phase transformation and sulfur/lithium diversity kinetics necessitate an all-inclusive approach in catalyst design. Herein, a compatible mediator with nanoscale-asymmetric-size configuration by integrating Co single atoms and defective CoTe 2–x (Co SA -CoTe 2–x @NHCF) is elaborately developed for regulating sulfur/lithium electrochemistry synchronously. Substantial electrochemistry and theoretical analyses reveal that CoTe 2–x exhibits higher catalytic activity in long-chain polysulfide transformation and Li 2 S decomposition, while monodispersed Co sites are more effective in boosting sulfur reduction kinetics to regulate Li 2 S deposition. Such cascade catalysis endows Co SA -CoTe 2–x @NHCF with the all-around service of “trapping-conversion-recuperation” for sulfur species during the whole redox reaction. Furthermore, it is demonstrated by in situ transmission electron microscopy that initially formed electronic-conductive Co and ionic-conductive Li 2 Te provide sufficient lithiophilic sites to regulate homogeneous Li plating and stripping with markedly suppressed dendrite growth. Consequently, by coupling the Co SA -CoTe 2–x @NHCF interlayer and Li@Co SA -CoTe 2–x @NHCF anode, the constructed Li–S full batteries deliver superior cycling stability and rate performance, and the flexible pouch cell exhibits stable cycling performance at 0.3 C. In conclusion, the gained insights into the synergistic effect of asymmetric-size structures pave the way for the integrated catalyst design in advanced Li–S systems.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Large off-diagonal magnetoelectricity in a triangular Co2+-based collinear antiferromagnet

Abstract Magnetic toroidicity is an uncommon type of magnetic structure in solid-state materials. Here, we experimentally demonstrate that collinear spins in a material with R -3 lattice symmetry can host a significant magnetic toroidicity, even parallel to the ordered spins. Taking advantage of a single crystal sample of CoTe 6 O 13 with an R -3 space group and a Co 2+ triangular sublattice, temperature-dependent magnetic, thermodynamic, and neutron diffraction results reveal A-type antiferromagnetic order below 19.5 K, with magnetic point group -3′ and k = (0,0,0). Our symmetry analysis suggests that the missing mirror symmetry in the lattice could lead to the local spin canting for a toroidal moment along the c axis. Experimentally, we observe a large off-diagonal magnetoelectric coefficient of 41.2 ps/m that evidences the magnetic toroidicity. In addition, the paramagnetic state exhibits a large effective moment per Co 2+ , indicating that the magnetic moment in CoTe 6 O 13 has a significant orbital contribution. CoTe 6 O 13 embodies an excellent opportunity for the study of next-generation functional magnetoelectric materials.

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

Mind the Gap: Building Simulation in the Architectural Design Studio

Building modelling and simulation approaches are increasingly being utilized in architectural design studios to guide and inform the design process and offer evidence-based feedback on proposed building performance. The development of intuitive and simplified simulation interfaces has greatly contributed to achieving this integration. One aspect that is often overlooked is the workflow that governs and regulates integrated design, which can have significant impacts on final design outcomes. Currently there are numerous software packages available for building performance simulations. This makes it challenging to select an appropriate tool that provides accurate results yet allows a designer to make informed architectural decisions with a designer-friendly interface. Furthermore, workflows to incorporate simulations into the design process proved to highly impact student’s project design integration. Yet, it is not clear what type of workflows are successful to achieve this goal, under what conditions, and/or for which building and site typologies. This paper addresses these issues by first reviewing three different workflows for integrating building performance simulation processes and highlighting their strengths and weaknesses. Second, a comparative case study approach was employed to test three of the most common workflows in three different integrated design architectural studios at the senior and vertical studio levels as well as in two courses that run parallel and complementary to the design studios. The workflows, processes, and the resultant student projects were further analyzed based on criteria for better integrated design and architectural excellence as outlined in the American Institute of Architects Committee on the Environment (AIA COTE) Top 10 Student’s Competition. Third, to situate the pedagogical case studies’ results within a larger context, a survey of the AIA COTE Top 10 student competition award recipients over the last five years was conducted. The results are summarized in a pedagogical framework that outlines best strategies of the type of workflows, software, design process used, methods to achieve desired interaction between design process and analytical feedback, and metrics for educators to evaluate the success of this integration and their learning outcomes in the design studio. The goal is to help bridge the gap between the building design and simulation within the design studio’s creative process for more integrated design outcomes.

Elzeyadi, Ihab↗
DOE OSTI2025

Significance of the structural configuration of B2 disorder in Co and Ti based Heusler alloys

We investigate here structural (at local and global levels) and transport properties for 𝑋 2 ⁢MnAl (𝑋= Co and Ti). Additionally, the magnetic properties were also studied for Ti 2 ⁢MnAl. Our x-ray diffraction results show that both the compounds stabilize in B2 disordered phase with cubic structure of 𝑃⁢𝑚⁢$\overline{3}$⁢𝑚 space group. Further, the structural configuration of the above disordered phase for both the compounds was identified using combined studies of x-ray absorption spectroscopy and multiple scattering calculations at the transition metal 𝐾 edges. Upon such identification, in the case of Co 2 ⁢Mn 1−𝑦⁢ Cr 𝑦 ⁢Al (𝑦= 0, 0.05, 0.1, 0.2) with change in 𝑦, we are able to establish a better connection quantitatively between the inverse of Mn-Co bonds and peak in the temperature-dependent resistivity. This highlights the crucial importance of a detailed understanding of the nature of B2 disorder. In the case of 𝑦=0, in the temperature range of study, the resistivity is driven by the functional form associated with (a) three-dimensional enhanced electron-electron Coulomb interaction scattering mechanism and (b) an unconventional one-magnon process. For Ti 2 ⁢MnAl, the transport shows metallic glasslike behavior at high temperature, while at low temperature it follows both the Cote-Meisel's model and quantum correction model. In this compound, the magnetic studies suggest the formation of superparamagnetic clusters in the paramagnetic matrix at low temperatures. Our density functional theory results are in line with the transport and magnetic properties. In literature, the spin polarization percentage (𝑃) for 𝑋= Co in B2 disordered phase is 76%. However, the present results emphasize the fact that in B2 disordered phase, the value of 𝑃 can range from 90% to 71% depending on the structural configuration introduced by swapping of the atomic positions of Mn and Al. For the compound under study, the value of percentage spin polarization obtained ranges between 82% to 85%. In addition, we also identify the origin of the difference in the shape of the Mn 3⁢𝑑 density of states for both the alloys. In conclusion, our results for 𝑋= Co alloy highlights the importance of identifying the specific structural configuration associated with a particular disorder category especially in the estimation of 𝑇 𝑐 and 𝑃 and for 𝑋= Ti, the physical properties can be tuned by varying the position of 𝐸 𝐹 and thereby its utilization in device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

From print to digital: Preserving over 10,000 McKibbin Cards

Collections management staff from the National Security Research Center (NSRC) recently digitized more than 10,000 McKibbin Cards to make them accessible on the Lab’s unclassified network, said NSRC collections management team leader Patricia Cote (WRS-NSRCMS). The cards, named after Dorothy McKibbin, who was known as the gatekeeper of Los Alamos because she was often the first point of contact for new hires, have become symbolic of the Lab when the world’s greatest minds secretly gathered to create the first atomic bomb and end World War II.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
DOE OSTI2025

exoALMA. XI. ALMA Observations and Hydrodynamic Models of LkCa 15: Implications for Planetary Mass Companions in the Dust Continuum Cavity

In the past decade, the Atacama Large Millimeter/submillimeter Array (ALMA) has revealed a plethora of substructures in the disks surrounding young stars. These substructures have several proposed formation mechanisms, with one leading theory being the interaction between the disk and newly formed planets. In this Letter, we present high angular resolution ALMA observations of LkCa 15’s disk that reveal a striking difference in dust and CO emission morphology. The dust continuum emission shows a ringlike structure characterized by a dust-depleted inner region of ~40 au in radius. Conversely, the CO emission is radially smoother and shows no sign of gas depletion within the dust cavity. We compare the observations with models for the disk–planet interaction, including radiative transfer calculation in the dust and CO emission. This source is particularly interesting, as the presence of massive planets within the dust cavity has been suggested based on previous near-IR observations. We find that the level of CO emission observed within the dust cavity is inconsistent with the presence of planets more massive than Jupiter orbiting between 10 and 40 au. Instead, we argue that the LkCa 15 innermost dust cavity might be created either by a chain of low-mass planets or by other processes that do not require the presence of planets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

The Photochemistry of Amino Acids Produced on the Polar Cryovolcanic Regions of Titan

The cryovolcanic regions of Titan offer transient opportunities for prebiotic molecules to exist in water–ammonia solutions on the surface of the Saturnian moon. The upcoming NASA’s Dragonfly mission will search for high nitrogen concentrations and amino acids on Titan’s equatorial terrains. Cryovolcanic features, however, are most common on the polar regions. To mitigate the distance, bubble bursting may encapsulate the prebiotic molecules into aerosols, which Titan’s Hadley circulation would subsequently transport to the equator. Here we investigate whether alanine and glycine survive this meridional journey. Despite the unconstrained meridional wind velocities, our results suggest that the amino acids can survive the transport through the mesosphere. Dragonfly may find cryo-volcanogenic amino acids on Titan’s equator. Further, the interaction between the two amino acids increased 10-fold the photodegradation rate of glycine. We justify it based on changes in the environment polarity.

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

Insulation or Irradiance: Exploring Why Bifacial Photovoltaics Run Hot

Bifacial photovoltaics are predicted to become the dominant device architecture over the next couple of years, but their thermal performance is not yet well understood. In this study, we model the thermal effects of different backside lamination materials on the performance of bifacial PERC cells. Glass-glass laminated cells were found to operate hotter than equivalent glass-polymer backsheet packed cells. This was solely due to the increased absorption of rear side incident light.

bifacial↗
DOE OSTI2025

Array-Based Seismic Measurements of OSIRIS-REx’s Re-Entry

The return home of the OSIRIS-REx spacecraft in September 2023 marked only the fifth time that an artificial object entered the Earth’s atmosphere at interplanetary velocities. Although rare, such events serve as valuable analogs for natural meteoroid re-entries; enabling study of hypersonic dynamics, shock wave generation, and acoustic-to-seismic coupling. Here, in this study, we report on the signatures recorded by a dense (100 m scale) 11-station array located almost directly underneath the capsule’s point of peak atmospheric heating in northern Nevada. Seismic data are presented, which allow inferences to be made about the shape of the shock wave’s footprint on the surface, the capsule’s trajectory, and its flight parameters.

58 GEOSCIENCES↗