Lithiated assemblies of metal chalcogenide nanowires
TL;DR: In this article, the van der Waals interactions between the nanowires are exploited to achieve intercalation without a significant change in their atomic structure, which can be used as cathode materials in Li-ion batteries for nanoscale applications.
Abstract: We study hexagonal assemblies of M6X6 (M=Mo and W and X=S, Se, and Te) nanowires from first-principles calculations to understand their structural stability, electronic properties, and the effects of Li intercalation. It is shown that due to van der Waals interactions between the nanowires, the intercalation is achieved without a significant change in their atomic structure. With an increase in Li concentration, we predict a new phase for Li3Mo6S6 compound, in which the hexagonal assembly transforms to a monoclinic structure by a change in the orientation of nanowires. The LixMo6S6 assemblies are electrically conductive and can be potentially used as cathode materials in Li-ion batteries for nanoscale applications. The voltage of such a battery, calculated to be 1.7V, can be manipulated such as by iodine doping without a significant change in the atomic structure.
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TL;DR: In this article, the authors focus on new nano-compositesinvolving Mo6 atom nanosized cluster units for optical, nanobiotechnology, energy and environmental applications.
Abstract: Recently, Nanoarchitectonics has been introducedas a new concept that refers to a technology systemfor arranging nanoscale structural units in a requiredarchitecture. Multifunctional properties are achieved by acombination of several materials in a well-defined architecture.In the frame of this concept, composite nanoarchitecturesrepresent a new class of nanostructured entitiesthat integrate various dissimilar nanoscale building blocksincluding clusters, particles, wires and films. The heterogeneouscomposite nanostructured materials are composedby definition of multi-(nano)components, each tailored toaddress different requirements. As one of the nanocomponents,nanometer sized metal clusters (<2 nm), whichconsist of less than a few dozens of metal atoms, could bedefined as a link between atom and nanoparticle. In thispaper, we will focus on our results on new nano-compositesinvolving Mo6 atom nanosized cluster units for optical,nanobiotechnology, energy and environmental applications.
93 citations
TL;DR: A novel phase transition, from multilayered 2H-MoTe2 to a parallel bundle of sub-nanometer-diameter metallic Mo6 Te6 nanowires (NWs) driven by catalyzer-free thermal-activation under vacuum, is demonstrated.
Abstract: A novel phase transition, from multilayered 2H-MoTe2 to a parallel bundle of sub-nanometer-diameter metallic Mo6 Te6 nanowires (NWs) driven by catalyzer-free thermal-activation (400-500 °C) under vacuum, is demonstrated. The NWs form along the 〈11-20〉 2H-MoTe2 crystallographic directions with lengths in the micrometer range. The metallic NWs can act as an efficient hole injection layer on top of 2H-MoTe2 due to favorable band-alignment. In particular, an atomically sharp MoTe2 /Mo6 Te6 interface and van der Waals gap with the 2H layers are preserved. The work highlights an alternative pathway for forming a new transition metal dichalcogenide phase and will enable future exploration of its intrinsic transportation properties.
59 citations
TL;DR: The van der Waals epitaxy of density-controlled single isolated 1T'-Mo6Te6 nanoplates on 2H-MoTe2 atomic layers by using metal-organic chemical vapor deposition leads to the possibility of ameliorating the high contact resistance faced by other TMDs and offers polymorphic structures for realizing higher-mobility TMD devices.
Abstract: High contact resistance between two-dimensional (2D) transition metal dichalcogenides (TMDs) and metal electrodes is a practical barrier for applications of 2D TMDs to conventional devices. A promising solution to this is polymorphic integration of 1T'-phase semimetallic and 2H-phase semiconducting TMD crystals, which can lower the Schottky barrier of the TMDs. Here, we demonstrate the van der Waals epitaxy of density-controlled single isolated 1T'-Mo6Te6 nanoplates on 2H-MoTe2 atomic layers by using metal-organic chemical vapor deposition. Importantly, in situ grown 1T'-Mo6Te6 nanoplates significantly reduce the contact resistance of the 2H-MoTe2 atomic layers, providing a record high mobility of 1139 cm2/V·s for Pd/1T'-Mo6Te6/2H-MoTe2 back-gated field-effect transistors, along with a low Schottky barrier height ( qϕb) of 8.7 meV. These results lead to the possibility of ameliorating the high contact resistance faced by other TMDs and, furthermore, offer polymorphic structures for realizing higher-mobility TMD devices.
18 citations
22 Feb 2021
TL;DR: The structures and stability of 66 atomic wires of 3d, 4d, and 5d transition metal chalcogenides in the M6X6 stoichiometry are explored, which allows atomically precise integration for flexible electronics and spintronics.
Abstract: As analogues of two-dimensional (2D) layered materials, searching for one-dimensional (1D) van der Waals wired materials as 1D Lego blocks for integration and device applications has been pursued. ...
13 citations
TL;DR: The efficiency of the combined use of quantum-chemical calculations and (95)Mo SSNMR experiments to study inorganic molybdenum cluster compounds is demonstrated, and the isotropic chemical shift of the Mo atoms is clearly correlated to their formal oxidation degree in the various clusters.
Abstract: The ability of (95)Mo solid-state nuclear magnetic resonance (SSNMR) spectroscopy to probe the atomic and electronic structures of inorganic molybdenum cluster materials has been demonstrated for the first time. Six cluster compounds were studied: MoBr(2), Cs(2)Mo(6)Br(14), (Bu(4)N)(2)Mo(6)Br(14), each containing the octahedral Mo(6)Br(14)(2-) cluster unit, and MoS(2)Cl(3), Mo(3)S(7)Cl(4), and MoSCl that contain metallic dimers, trimers, and tetramers, respectively. To overcome inherent difficulties due to the low sensitivity of (95)Mo SSNMR, both high-magnetic-field spectrometers and the quadrupolar Carr-Purcell Meiboom-Gill sensitivity enhancement pulse sequence under magic-angle-spinning conditions, combined with a hyperbolic-secant pulse were used. Experimental measurements as well as characterization of the (95)Mo electric field gradient and chemical shift tensors have been performed with the help of quantum-chemical calculations under periodic boundary conditions using the projector augmented-wave and the gauge-including projector augmented-wave methods, respectively. A large (95)Mo chemical shift range is measured, ∼3150 ppm, and the isotropic chemical shift of the Mo atoms is clearly correlated to their formal oxidation degree in the various clusters. Furthermore, a direct relation is evidenced between the molybdenum quadrupolar coupling constant and the bond lengths with its surrounding ligands. Our results demonstrate the efficiency of the combined use of quantum-chemical calculations and (95)Mo SSNMR experiments to study inorganic molybdenum cluster compounds.
12 citations
References
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TL;DR: Novel features are that the pseudopotential itself becomes charge-state dependent, the usual norm-conservation constraint does not apply, and a generalized eigenproblem is introduced.
Abstract: A new approach to the construction of first-principles pseudopotentials is described. The method allows transferability to be improved systematically while holding the cutoff radius fixed, even for large cutoff radii. Novel features are that the pseudopotential itself becomes charge-state dependent, the usual norm-conservation constraint does not apply, and a generalized eigenproblem is introduced. The potentials have a separable form well suited for plane-wave solid-state calculations, and show promise for application to first-row and transition-metal systems.
18,782 citations
TL;DR: A way is found to visualize and understand the nonlocality of exchange and correlation, its origins, and its physical effects as well as significant interconfigurational and interterm errors remain.
Abstract: Generalized gradient approximations (GGA's) seek to improve upon the accuracy of the local-spin-density (LSD) approximation in electronic-structure calculations. Perdew and Wang have developed a GGA based on real-space cutoff of the spurious long-range components of the second-order gradient expansion for the exchange-correlation hole. We have found that this density functional performs well in numerical tests for a variety of systems: (1) Total energies of 30 atoms are highly accurate. (2) Ionization energies and electron affinities are improved in a statistical sense, although significant interconfigurational and interterm errors remain. (3) Accurate atomization energies are found for seven hydrocarbon molecules, with a rms error per bond of 0.1 eV, compared with 0.7 eV for the LSD approximation and 2.4 eV for the Hartree-Fock approximation. (4) For atoms and molecules, there is a cancellation of error between density functionals for exchange and correlation, which is most striking whenever the Hartree-Fock result is furthest from experiment. (5) The surprising LSD underestimation of the lattice constants of Li and Na by 3--4 % is corrected, and the magnetic ground state of solid Fe is restored. (6) The work function, surface energy (neglecting the long-range contribution), and curvature energy of a metallic surface are all slightly reduced in comparison with LSD. Taking account of the positive long-range contribution, we find surface and curvature energies in good agreement with experimental or exact values. Finally, a way is found to visualize and understand the nonlocality of exchange and correlation, its origins, and its physical effects.
17,848 citations
Book•
01 Jan 1996
TL;DR: In this paper, the authors present a detailed overview of the properties of Fullerenes and their properties in surface science applications, such as scanning tunnel microscopy, growth and fragmentation studies, and chemical synthesis.
Abstract: Historical Introduction. Carbon Materials. Structure of Fullerenes. Symmetry Considerations. Growth and Fragmentation Studies. Crystalline Structure of Fullerenes. Synthesis of Fullerene Molecules and Solids. Doping of Fullerenes. Structure of Doped Fullerenes and Fullerene Compounds. Fullerene Chemistry. Vibrational Modes. Thermal Properties. Electronic Structure. Optical Properties. Electrical and Thermal Properties. Superconductivity. Nuclear Magnetic Resonance Studies. Electron Paramagnetic Resonance. Surface Science Techniques on Fullerenes. Magnetic Properties. Fullerene-Related Tubules and Spherules. Scanning Tunnel Microscopy. Applications.
4,008 citations
TL;DR: In this paper, the authors proposed a pseudowave function inside the cut-off radius with the concept of ultrasoft pseudopotentials introduced by Vanderbilt optimal compromise between transferability and plane-wave convergence.
Abstract: The construction of accurate pseudopotentials with good convergence properties for the first-row and transition elements is discussed. We show that by combining an improved description of the pseudowavefunction inside the cut-off radius with the concept of ultrasoft pseudopotentials introduced by Vanderbilt optimal compromise between transferability and plane-wave convergence can be achieved. With the new pseudopotentials, basis sets with no more than 75-100 plane waves per atom are sufficient to reproduce the results obtained with the most accurate norm-conserving pseudopotentials.
3,263 citations
TL;DR: This work shows that basic components, the electrode, separator, and electrolyte, can all be integrated into single contiguous nanocomposite units that can serve as building blocks for a variety of thin mechanically flexible energy storage devices.
Abstract: There is strong recent interest in ultrathin, flexible, safe energy storage devices to meet the various design and power needs of modern gadgets. To build such fully flexible and robust electrochemical devices, multiple components with specific electrochemical and interfacial properties need to be integrated into single units. Here we show that these basic components, the electrode, separator, and electrolyte, can all be integrated into single contiguous nanocomposite units that can serve as building blocks for a variety of thin mechanically flexible energy storage devices. Nanoporous cellulose paper embedded with aligned carbon nanotube electrode and electrolyte constitutes the basic unit. The units are used to build various flexible supercapacitor, battery, hybrid, and dual-storage battery-in-supercapacitor devices. The thin freestanding nanocomposite paper devices offer complete mechanical flexibility during operation. The supercapacitors operate with electrolytes including aqueous solvents, room temperature ionic liquids, and bioelectrolytes and over record temperature ranges. These easy-to-assemble integrated nanocomposite energy-storage systems could provide unprecedented design ingenuity for a variety of devices operating over a wide range of temperature and environmental conditions.
1,097 citations