SEARCH · Engineering Papers
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.
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
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
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
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
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
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
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
Abstract Polaritons in hyperbolic van der Waals materials—where principal axes have permittivities of opposite signs—are light-matter modes with unique properties and promising applications. Isofrequency contours of hyperbolic polaritons may undergo topological transitions from open hyperbolas to closed ellipse-like curves, prompting an abrupt change in physical properties. Electronically-tunable topological transitions are especially desirable for future integrated technologies but have yet to be demonstrated. In this work, we present a doping-induced topological transition effected by plasmon-phonon hybridization in graphene/α-MoO 3 heterostructures. Scanning near-field optical microscopy was used to image hybrid polaritons in graphene/α-MoO 3 . We demonstrate the topological transition and characterize hybrid modes, which can be tuned from surface waves to bulk waveguide modes, traversing an exceptional point arising from the anisotropic plasmon-phonon coupling. Graphene/α-MoO 3 heterostructures offer the possibility to explore dynamical topological transitions and directional coupling that could inspire new nanophotonic and quantum devices.
Explore the source record for details and available documents.
(MoO3)3H2O crystallizes in the triclinic P-1 space group. The structure is three-dimensional and consists of two water molecules and one MoO3 framework. In the MoO3 framework, there are three inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.72–2.39 Å. In the second Mo6+ site, Mo6+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing MoO6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are a spread of Mo–O bond distances ranging from 1.72–2.27 Å. In the third Mo6+ site, Mo6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.72–2.34 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to two Mo6+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Mo6+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Mo6+ atoms.
(MoO3)12N2 crystallizes in the trigonal P3 space group. The structure is three-dimensional and consists of one ammonia molecule and one MoO3 framework. In the MoO3 framework, Mo+5.50+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.70–2.47 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Mo+5.50+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Mo+5.50+ atoms. There are one shorter (1.75 Å) and one longer (2.47 Å) O–Mo bond lengths. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Mo+5.50+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Mo+5.50+ atoms. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Mo+5.50+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one Mo+5.50+ atom. The O–Mo bond length is 1.70 Å.
Na(MoO3)4O2 crystallizes in the monoclinic C2 space group. The structure is three-dimensional and consists of two hydrogen peroxide molecules and one Na(MoO3)4 framework. In the Na(MoO3)4 framework, Na is bonded in a distorted square co-planar geometry to four O atoms. All Na–O bond lengths are 2.42 Å. There are two inequivalent Mo sites. In the first Mo site, Mo is bonded to six O atoms to form distorted MoO6 octahedra that share corners with five equivalent MoO5 trigonal bipyramids and an edgeedge with one MoO6 octahedra. There are a spread of Mo–O bond distances ranging from 1.73–2.30 Å. In the second Mo site, Mo is bonded to five O atoms to form distorted corner-sharing MoO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 13–69°. There are a spread of Mo–O bond distances ranging from 1.72–1.97 Å. There are six inequivalent O sites. In the first O site, O is bonded in a linear geometry to two Mo atoms. In the second O site, O is bonded in a linear geometry to two Mo atoms. In the third O site, O is bonded in a distorted bent 150 degrees geometry to two Mo atoms. In the fourth O site, O is bonded in a distorted trigonal planar geometry to three Mo atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to one Na and one Mo atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Na and one Mo atom.
(MoO3)3N2SeO3 crystallizes in the hexagonal P6_3 space group. The structure is two-dimensional and consists of four ammonia molecules; two SeO3 clusters; and two MoO3 sheets oriented in the (0, 0, 1) direction. In each SeO3 cluster, Se2- is bonded in a trigonal planar geometry to three equivalent O2- atoms. All Se–O bond lengths are 1.63 Å. O2- is bonded in a single-bond geometry to one Se2- atom. In each MoO3 sheet, Mo6+ is bonded to five O2- atoms to form distorted corner-sharing MoO5 square pyramids. There are a spread of Mo–O bond distances ranging from 1.70–2.02 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Mo6+ atoms. In the second O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Mo6+ atoms.
(MoO3)4N2(NO)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two ammonia molecules, two nitroxyl molecules, and one MoO3 cluster. In the MoO3 cluster, there are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form corner-sharing MoO4 tetrahedra. There are a spread of Mo–O bond distances ranging from 1.72–1.93 Å. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form corner-sharing MoO4 tetrahedra. There are a spread of Mo–O bond distances ranging from 1.72–1.93 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Mo6+ atoms. In the second O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Mo6+ atoms. In the sixth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom.
Halide perovskite solar cells (PSCs) exhibit commercialization potential, but long-term stability still must be addressed. Among various products of perovskite decomposition, iodine species are of considerable concern due to their high vapor pressure and corrosive nature. To address this, a small-molecule hole transport layer (HTL), 4,4',4"-tris[(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), is used; mixing it with molybdenum trioxide (MoO3) p-dopes the layer and slows iodine permeation. Furthermore, we demonstrate that m-MTDATA:MoO3 HTLs employed in PSCs improve stability under both thermal and voltage bias stress compared to devices with a conventional doped 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD) HTL.
MoO3Al is (Cubic) Perovskite structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional and consists of one aluminum molecule and one MoO3 framework. In the MoO3 framework, Mo3+ is bonded to six equivalent O2- atoms to form corner-sharing MoO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.00 Å) and two longer (2.01 Å) Mo–O bond lengths. O2- is bonded in a linear geometry to two equivalent Mo3+ atoms.
Mechanochemistry and mechanocatalysis are gaining increasing attention as environmentally friendly chemical processes because of their solvent-free nature and scalability. Significant effort has been devoted for studying continuum-scale phenomena in mechanochemistry, such as temperature and pressure gradients, but the atomic-scale mechanisms remain relatively unexplored. In this work, we focus on the mechanochemical reduction of MoO3 as a case study. We use experimental techniques to determine the mechanochemical reduction conditions and density functional theory (DFT) simulations to establish an atomistic framework for identifying the metastable surfaces that are most likely to enable this process. Our results show that metastable surfaces can significantly lower or remove thermodynamic barriers for surface reduction and that kinetic energy from milling can facilitate the formation of metastable surfaces that have high surface fracture energies and are not thermally accessible. These findings indicate that metastable surfaces are an important aspect of mechanochemistry along with hot spots and other continuum-scale phenomena.