Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “planar structures”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Characterization of the Interfacial Orientation and Molecular Conformation in a Glass-Forming Organic Semiconductor

The ability to control structure in molecular glasses has enabled them to play a key role in modern technology; in particular, they are ubiquitous in organic light-emitting diodes. While the interplay between bulk structure and optoelectronic properties has been extensively investigated, few studies have examined molecular orientation near buried interfaces despite its critical role in emergent functionality. Direct, quantitative measurements of buried molecular orientation are inherently challenging, and many methods are insensitive to orientation in amorphous soft matter or lack the necessary spatial resolution. To overcome these challenges, we use polarized resonant soft X-ray reflectivity (pRSoXR) to measure nanometer-resolved, molecular orientation depth profiles of vapor-deposited thin films of an organic semiconductor Tris(4-carbazoyl-9-ylphenyl)amine (TCTA). Our depth profiling approach characterizes the vertical distribution of molecular orientation and reveals that molecules near the inorganic substrate and free surface have a different, nearly isotropic orientation compared to those of the anisotropic bulk. Comparison of pRSoXR results with near-edge X-ray absorption fine structure spectroscopy and optical spectroscopies reveals that TCTA molecules away from the interfaces are predominantly planar, which may contribute to their attractive charge transport qualities. Buried interfaces are further investigated in a TCTA bilayer (each layer deposited under separate conditions resulting in different orientations) in which we find a narrow interface between orientationally distinct layers extending across ≈1 nm. Coupling this result with molecular dynamics simulations provides additional insight into the formation of interfacial structure. This study characterizes the local molecular orientation at various types of buried interfaces in vapor-deposited glasses and provides a foundation for future studies to develop critical structure–function relationships.

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

Materials Data on BaCa4(CoN2)2 by Materials Project

BaCa4(CoN2)2 crystallizes in the tetragonal P4/ncc space group. The structure is three-dimensional. Ba2+ is bonded in a square co-planar geometry to four equivalent N3- atoms. All Ba–N bond lengths are 2.93 Å. Ca2+ is bonded to four equivalent N3- atoms to form a mixture of corner and edge-sharing CaN4 trigonal pyramids. There are a spread of Ca–N bond distances ranging from 2.43–2.55 Å. Co1+ is bonded in a linear geometry to two equivalent N3- atoms. Both Co–N bond lengths are 1.79 Å. N3- is bonded in a 6-coordinate geometry to one Ba2+, four equivalent Ca2+, and one Co1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuPO4 by Materials Project

CuPO4 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. Cu3+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.88 Å. P5+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All P–O bond lengths are 1.55 Å. O2- is bonded in a bent 120 degrees geometry to one Cu3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In2CuO4 by Materials Project

CuIn2O4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.92 Å. In3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are four shorter (2.21 Å) and four longer (2.59 Å) In–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to two equivalent Cu2+ and four equivalent In3+ atoms. In the second O2- site, O2- is bonded to four equivalent In3+ atoms to form a mixture of edge and corner-sharing OIn4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZnCu2O3 by Materials Project

Cu2ZnO3 crystallizes in the orthorhombic Pmmn space group. The structure is three-dimensional. Cu2+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Cu–O bond distances ranging from 1.93–1.98 Å. Zn2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Zn–O bond distances ranging from 2.07–2.60 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Cu2+ and two equivalent Zn2+ atoms to form distorted corner-sharing OZn2Cu2 tetrahedra. In the second O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Cu2+ and two equivalent Zn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Improved Crystalline Structure and Enhanced Photoluminescence of ZnO Nanolayers in B i2 Se 3 /ZnO Heterostructures

The Bi 2 Se 3 /ZnO heterostructure is a new combination of high- and low-band-gap nanomaterials that can be implemented for optoelectronic devices. The influence of the Bi 2 Se 3 substrate on crystallization of ZnO nanolayers and charge separation at the Bi 2 Se 3 /ZnO interface reflects these important parameters, which affect optical and electronic properties of the heterostructure. Despite a few studies on Bi 2 Se 3 /ZnO heterostructures, the mechanisms of enhanced optical properties and correlation between optical and structural properties in such heterostructures are not studied in detail. In the present paper, we report on structure and optical properties of ZnO nanolayers with different thicknesses (10–150 nm) deposited by atomic layer deposition on planar and nonplanar Bi 2 Se 3 nanostructured coatings. Crystallization of ZnO nanolayers grown on Bi 2 Se 3 and Si substrates was analyzed by X-ray diffraction and scanning and transmission electron microscopy methods. Enhancement of ZnO photoluminescence in Bi 2 Se 3 /ZnO heterostructures in comparison to the photoluminescence of ZnO nanolayers of the same thickness deposited on p-doped Si substrates was observed. Correlation between the structure and optical properties of ZnO nanolayers in Bi 2 Se 3 /ZnO heterostructures is analyzed. Three complementary mechanisms of enhancement of optical properties of ZnO in Bi 2 Se 3 /ZnO heterostructures, based on charge separation at the Bi 2 Se 3 /ZnO interface, improvement of ZnO crystalline structure, and surface-plasmon–photon coupling, are proposed. The Bi 2 Se 3 /ZnO heterostructure is a new combination of high- and low-band-gap nanomaterials that can be implemented for optoelectronic devices. The influence of the Bi 2 Se 3 substrate on crystallization of ZnO nanolayers and charge separation at the Bi 2 Se 3 /ZnO interface reflects these important parameters, which affect optical and electronic properties of the heterostructure. Despite a few studies on Bi 2 Se 3 /ZnO heterostructures, the mechanisms of enhanced optical properties and correlation between optical and structural properties in such heterostructures are not studied in detail. In the present paper, we report on structure and optical properties of ZnO nanolayers with different thicknesses (10–150 nm) deposited by atomic layer deposition on planar and nonplanar Bi 2 Se 3 nanostructured coatings. Crystallization of ZnO nanolayers grown on Bi 2 Se 3 and Si substrates was analyzed by X-ray diffraction and scanning and transmission electron microscopy methods. Enhancement of ZnO photoluminescence in Bi 2 Se 3 /ZnO heterostructures in comparison to the photoluminescence of ZnO nanolayers of the same thickness deposited on p-doped Si substrates was observed. Correlation between the structure and optical properties of ZnO nanolayers in Bi 2 Se 3 /ZnO heterostructures is analyzed. Finally, three complementary mechanisms of enhancement of optical properties of ZnO in Bi 2 Se 3 /ZnO heterostructures, based on charge separation at the Bi 2 Se 3 /ZnO interface, improvement of ZnO crystalline structure, and surface-plasmon–photon coupling, are proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Relaxing Wrinkles in Jammed Interfacial Assemblies

Dynamic covalent bonding has emerged as a mean by which stresses in a network can be relaxed. Here, the strength of the bonding of ligands to nanoparticles at the interface between two immiscible liquids affect the same results in jammed assemblies of nanoparticle surfactants. Beyond a critical degree of overcrowding induced by the compression of jammed interfacial assemblies, the bonding of ligands to nanoparticles (NPs) can be broken, resulting in a desorption of the NPs from the interface. This reduces the areal density of nanoparticle surfactants at the interface, allowing the assemblies to relax, not to a fluid state but rather another jammed state. The relaxation of the wrinkles caused by the compression reflects the tendency of these assemblies to eliminate areas of high curvature, favoring a more planar geometry. Importantly, this enabled the generation of giant vesicular and multivesicular structures from these assemblies.

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

Reticular exploration of uranium-based metal—organic frameworks with hexacarboxylate building units

We report that the rational reticular design of metal–organic frameworks (MOFs) from building units of known geometries is essential for enriching the diversity of MOF structures. Unexpected and intriguing structures, however, can also arise from subtle changes in the rigidity/length of organic linkers and/or synthetic conditions. Herein, we report three uranium-based MOF structures—i.e., NU-135X (X = 0, 1, 2)—synthesized from trigonal planar uranyl nodes and triptycene-based hexacarboxylate ligands with variable arm lengths. A new chiral 3,6-connected nuc net was observed in NU-1350, while the extended versions of the ligand led to 3-fold catenated MOFs (NU-1351 and NU-1352) with rare 3,6-connected cml-c3 nets. Lastly, the differences in the topology of NU-1350 and NU-1351/NU-1352 could be attributed to the slight distortions of the shorter linker in the former from the ideal trigonal prism geometry to an octahedral geometry when coordinated to the trigonal planar uranyl nodes.

3,6-connected net↗
DOE OSTI2022

Crystal structure of halofuginone hydrobromide, C 16 H 18 BrClN 3 O 3 Br

The crystal structure of one form of halofuginone hydrobromide has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Halofuginone hydrobromide crystallizes in space group P2 1 (#4) with a = 8.87398(13), b = 14.25711(20), c = 15.0153(3) Å, β = 91.6867(15)°, V = 1898.87(4) Å 3 , and Z = 4. The crystal structure consists of alternating layers (parallel to the ab-plane) of planar and nonplanar portions of the cations. N–H∙∙∙Br and O–H∙∙∙Br hydrogen bonds link the protonated piperidine rings and bromide anions into a two-dimensional network parallel to the ab-plane. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stacking faults and alternate crystal structures for the shape-memory alloy NiTi

Here, we use ab initio calculations to study the role of stacking faults in connecting the high-temperature B2 and the theoretically predicted low-temperature B33 NiTi phases. In contrast with prior work, we describe the B 2 → B 33 phase transformation in terms of alternate bilayer shifts by 1 2 [100] on the ( 011 ) B 2 plane, obtaining a viable pathway; the same mechanism could also work with the B19 parent phase. We then examine B33-like structures built from alternate stacking sequences of B19 bilayers, constructed to have monoclinic tilt angles close to the experimentally reported NiTi B19' martensite, and find four low-energy stacking-fault variants with energies 5.8–8.5 meV/atom above the calculated B19' martensite structure, suggesting that such structures might appear as a part of the NiTi martensite phase at low temperatures. Investigating further the occurrence of specific coordinated planar shifts in NiTi systems, we report a dynamically stable NiTi B27 phase and find that it is only 1.2 meV/atom above the calculated B33 ground-state structure, thus having a potential to also play a role in NiTi martensitic phase transformation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Lithiation of Sulfur-Graphene Compounds Using Reactive Force-Field Molecular Dynamics Simulations

We performed molecular dynamics simulations of lithium-sulfur-graphene compounds using reactive force fields, providing a time scale to observe atomistic features relevant to the microscopic behavior of the of the bulk of sulfur-based cathodes to be used beyond our present Li-ion batteries. The samples we used were set to realistic geometries through sophisticated protocols to simulate ultrafast reactions that occur within the picosecond range, thus allowing us to get some insights into the characteristics of the bulk material in working cathodes of Li–S batteries, which are mixed with carbon to increase the poor electronic conductivity of S. We report chemical speciation and geometrical data at atomistic levels. We observed that slowly lithiated cathodes were more stable and with higher density than those that were suddenly fully-lithiated. We did not observe molecular Li 2 S formation; however, we observed an amorphous solid arrangement with the same stoichiometry of Li and S, with S–Li–S angles of ~111° and smaller ones due to the interaction between polysulfides that did not reacted totally. In addition, graphene keeps its planar shape; however, S8 changes its shape from rings to chains. Lithiated structures are more stable with lower energies, and more close-packed structures than structures with Li already inserted.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on LaPt3 by Materials Project

LaPt3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. La2+ is bonded to twelve equivalent Pt+0.67- atoms to form a mixture of face and corner-sharing LaPt12 cuboctahedra. All La–Pt bond lengths are 3.00 Å. Pt+0.67- is bonded in a distorted square co-planar geometry to four equivalent La2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NpSi3 by Materials Project

NpSi3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Np4+ is bonded to twelve equivalent Si+1.33- atoms to form a mixture of face and corner-sharing NpSi12 cuboctahedra. All Np–Si bond lengths are 2.83 Å. Si+1.33- is bonded in a distorted square co-planar geometry to four equivalent Np4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnSe2 by Materials Project

MnSe2 crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Mn4+ is bonded to six equivalent Se2- atoms to form corner-sharing MnSe6 octahedra. The corner-sharing octahedral tilt angles are 62°. All Mn–Se bond lengths are 2.55 Å. Se2- is bonded in a distorted trigonal planar geometry to three equivalent Mn4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnTe2 by Materials Project

MnTe2 is Pyrite structured and crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Mn4+ is bonded to six equivalent Te2- atoms to form corner-sharing MnTe6 octahedra. The corner-sharing octahedral tilt angles are 62°. All Mn–Te bond lengths are 2.76 Å. Te2- is bonded in a distorted trigonal planar geometry to three equivalent Mn4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on USi3 by Materials Project

USi3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. U4+ is bonded to twelve equivalent Si+1.33- atoms to form a mixture of face and corner-sharing USi12 cuboctahedra. All U–Si bond lengths are 2.85 Å. Si+1.33- is bonded in a distorted square co-planar geometry to four equivalent U4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YbPt3 by Materials Project

YbPt3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Yb2+ is bonded to twelve equivalent Pt+0.67- atoms to form a mixture of face and corner-sharing YbPt12 cuboctahedra. All Yb–Pt bond lengths are 2.88 Å. Pt+0.67- is bonded in a distorted square co-planar geometry to four equivalent Yb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgPt3 by Materials Project

MgPt3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Mg2+ is bonded to twelve equivalent Pt+0.67- atoms to form a mixture of face and corner-sharing MgPt12 cuboctahedra. All Mg–Pt bond lengths are 2.81 Å. Pt+0.67- is bonded in a distorted square co-planar geometry to four equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗