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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.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Energy level alignment at the methylammonium lead iodide/copper phthalocyanine interface

The energy level alignment at the CH{sub 3}NH{sub 3}PbI{sub 3}/copper phthalocyanine (CuPc) interface is investigated by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). XPS reveal a 0.3 eV downward band bending in the CuPc film. UPS validate this finding and further reveal negligible interfacial dipole formation – verifying the viability of vacuum level alignment. The highest occupied molecular orbital of CuPc is found to be closer to the Fermi level than the valance band maximum of CH{sub 3}NH{sub 3}PbI{sub 3}, facilitating hole transfer from CH{sub 3}NH{sub 3}PbI{sub 3} to CuPc. However, subsequent hole extraction from CuPc may be impeded by the downward band bending in the CuPc layer.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Modeling and Optimization of Trip Level Energy Consumption and Charging Management for Connected Automated Electric Vehicles

This will be a presentation for a tutorial session in 2019 ITEC based on reviewing the publicly existing work in the literature. Trip aware energy consumption and charging management for electric vehicles is a key component to ensure sustainability of electrified transportation. The upcoming vehicle communication and autonomous driving technologies will provide opportunities to achieve more intelligent management strategies. This tutorial will introduce the state-to-art technologies that are being designed for optimizing the trip level energy cost and recharging operations of connected automated electric vehicles (CAEVs). The information needs, modeling, control and optimization techniques for optimal trip level energy management will be introduced. Opportunities and benefits from vehicle communication and automation will be discussed. In general, three main sub-topics will be presented in detail: first, advanced EV energy consumption modeling and prediction technologies; second, energy efficient driving technologies, e.g. eco-driving and eco-routing, etc.; third, optimally automatic charging decision making for CAEVs. Following these details, the research challenges, opportunities for co-optimization between the energy consumption and energy recharging of CAEVs will be illustrated in this tutorial.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Seleno groups control the energy-level alignment between conjugated organic molecules and metals

The charge injection from metallic electrodes into hole transporting layers of organic devices often suffers from deviations from vacuum-level alignment at the interface. Even for weakly interacting cases, Pauli repulsion causes an interface dipole between the metal and conjugated organic molecules (COMs) (so called “push-back” or “cushion” effect), which leads notoriously to an increase of the hole injection barrier. On the other hand, for chalcogenol self assembled monolayers (SAMs) on metal surfaces, chemisorption via the formation of chalcogen-metal bonds is commonly observed. In these cases, the energy-level alignment is governed by chalcogen-derived interface states in the vicinity of the metal Fermi-level. In this work, we present X-ray and ultraviolet photoelectron spectroscopy data that demonstrate that the interfacial energy-level alignment mechanism found for chalcogenol SAMs also applies to seleno-functionalized COMs. This can be exploited to mitigate the push-back effect at metal contacts, notably also when COMs with low ionization energies are employed, permitting exceedingly low hole injection barriers, as shown here for the interfaces of tetraseleno-tetracene with Au(111), Ag(111), and Cu(111)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Energy level alignment and quantum conductance of functionalized metal-molecule junctions: Density functional theory versus GW calculations

We study the effect of functional groups (CH{sub 3}*4, OCH{sub 3}, CH{sub 3}, Cl, CN, F*4) on the electronic transport properties of 1,4-benzenediamine molecular junctions using the non-equilibrium Green function method. Exchange and correlation effects are included at various levels of theory, namely density functional theory (DFT), energy level-corrected DFT (DFT+Σ), Hartree-Fock and the many-body GW approximation. All methods reproduce the expected trends for the energy of the frontier orbitals according to the electron donating or withdrawing character of the substituent group. However, only the GW method predicts the correct ordering of the conductance amongst the molecules. The absolute GW (DFT) conductance is within a factor of two (three) of the experimental values. Correcting the DFT orbital energies by a simple physically motivated scissors operator, Σ, can bring the DFT conductances close to experiments, but does not improve on the relative ordering. We ascribe this to a too strong pinning of the molecular energy levels to the metal Fermi level by DFT which suppresses the variation in orbital energy with functional group.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Energy levels, wavelengths, and transition rates of multipole transitions (E1, E2, M1, M2) in Au{sup 67+} and Au{sup 66+} ions

The fully relativistic configuration interaction method of the FAC code is used to calculate atomic data for multipole transitions in Mg-like Au (Au{sup 67+}) and Al-like Au (Au{sup 66+}) ions. Generated atomic data are important in the modeling of M-shell spectra for heavy Au ions and Au plasma diagnostics. Energy levels, oscillator strengths and transition rates are calculated for electric-dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) for transitions between excited and ground states 3l−nl{sup ′}, such that n=4,5,6,7. The local central potential is derived using the Dirac–Fock–Slater method. Correlation effects to all orders are considered by the configuration interaction expansion. All relativistic effects are included in the calculations. Calculated energy levels are compared against published values that were calculated using the multi-reference many body perturbation theory, which includes higher order QED effects. Favorable agreement was observed, with less than 0.15% difference.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Multiconfiguration Dirac–Hartree–Fock energy levels, weighted oscillator strengths, transitions probabilities, lifetimes, hyperfine constants, Landé g-factors and isotope shifts of Xe LIII

Energy levels, weighted oscillator strengths and transition probabilities, lifetimes, hyperfine interaction constants, Landé g{sub J} factors and isotope shifts are calculated for all levels of 1s{sup 2} and 1snl (n=2−7) configurations of He-like xenon ion (Xe LIII). Multiconfigurational Dirac–Hartree–Fock (MCDHF) method is adopted for calculating these spectroscopic data. Comparisons are made with similar data obtained with FAC (Flexible Atomic Code) to assess the accuracy of the results. Transition probabilities are reported for all E1, E2, M1 and M2 transitions from the ground level. Breit interactions and quantum electrodynamics effects are estimated in extensive Relativistic Configuration Interaction (RCI) calculations. Comparisons were made with the available data in the literature and good agreement was found which confirms the reliability of our results. The accuracy of the present calculations is high enough to facilitate identification of many observed spectral lines. Almost all atomic data of He-like xenon ion presented in this paper are calculated for the first time.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Energy levels distribution in supersaturated silicon with titanium for photovoltaic applications

In the attempt to form an intermediate band in the bandgap of silicon substrates to give it the capability to absorb infrared radiation, we studied the deep levels in supersaturated silicon with titanium. The technique used to characterize the energy levels was the thermal admittance spectroscopy. Our experimental results showed that in samples with titanium concentration just under Mott limit there was a relationship among the activation energy value and the capture cross section value. This relationship obeys to the well known Meyer-Neldel rule, which typically appears in processes involving multiple excitations, like carrier capture/emission in deep levels, and it is generally observed in disordered systems. The obtained characteristic Meyer-Neldel parameters were Tmn = 176 K and kTmn = 15 meV. The energy value could be associated to the typical energy of the phonons in the substrate. The almost perfect adjust of all experimental data to the same straight line provides further evidence of the validity of the Meyer Neldel rule, and may contribute to obtain a deeper insight on the ultimate meaning of this phenomenon.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

High-Performance n-type Organic Semiconductors: Incorporating Specific Electron-Withdrawing Motifs to Achieve Tight Molecular Stacking and Optimized Energy Levels

Novel {pi}-conjugated cyanostilbene-based semiconductors (Hex-3,5-TFPTA and Hex-4-TFPTA) with tight molecular stacking and optimized energy levels are synthesized. Hex-4-TFPTA exhibits high-performance n-type organic field-effect transistor (OFET) properties with electron mobilities as high as 2.14 cm{sup 2} V{sup -1}s{sup -1} and on-off current ratios >10{sup 6}.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Energy levels and radiative rates for transitions in Cr-like Co IV and Ni V

We report calculations of energy levels and radiative rates (A-values) for transitions in Cr-like Co IV and Ni V. The quasi-relativistic Hartree–Fock (QRHF) code is adopted for calculating the data although grasp (general-purpose relativistic atomic structure package) and flexible atomic code (fac) have also been employed for comparison purposes. No radiative rates are available in the literature to compare with our results, but our calculated energies are in close agreement with those compiled by NIST for a majority of the levels. However, there are discrepancies for a few levels of up to 3%. The A-values are listed for all significantly contributing E1, E2 and M1 transitions, and the corresponding lifetimes reported, although unfortunately no previous theoretical or experimental results exist to compare with our data.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Degeneracy of energy levels of pseudo-Gaussian oscillators

We study the main features of the isotropic radial pseudo-Gaussian oscillators spectral properties. This study is made upon the energy levels degeneracy with respect to orbital angular momentum quantum number. In a previous work [6] we have shown that the pseudo-Gaussian oscillators belong to the class of quasi-exactly solvable models and an exact solution has been found.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Energy level transitions of gas in a 2D nanopore

An analytical study of gas behavior in a 2D nanopore was performed. It is shown that the temperature dependence of gas energy can be stepwise due to transitions from one size-quantized subband to another. Taking into account quantum size effects results in energy level transitions governed by the nanopore size, temperature and gas density. This effect leads to an abrupt change of gas heat capacity in the nanopore at the above varying system parameters.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1984

Variational calculations of muonic-molecule energy levels

The best variational energies obtained to date of the bound states of muonic molecules containing nucleons of unit charge or isotopes of hydrogen are reported. Hylleraas wave functions are used to describe the three-particle systems, and the convergence of the energies is carefully studied; as many as 440 terms have been included in some cases. These results are compared with the best previous values.

Bhatia, A. K.↗
DOE OSTI2015

Systematic calculations of energy levels and transition rates of BE-like ions with Z = 10–30 using a combined configuration interaction and many-body perturbation theory approach

We report calculations of energy levels and radiative rates for transitions among the lowest 116 fine-structure levels arising from the n⩽5 configurations in Be-like ions with Z = 10–30. The wavelengths, oscillator strengths, line strengths, and radiative rates for all possible electric dipole, magnetic dipole, electric quadrupole, and magnetic quadrupole transitions among the 116 levels have been calculated using the combined configuration interaction and many-body perturbation method. The accuracy of the results is determined through extensive comparisons with existing laboratory measurements and theoretical results. The present complete set of results should be of great help in line identification and the interpretation of spectra, as well as in the modeling and diagnostics of astrophysical and fusion plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗