Search results for " orbita"
showing 10 items of 447 documents
Spinterface: Crafting spintronics at the molecular scale
2014
A number of studies have suggested that molecular materials could offer similar performance as, or even potentially supersede, those of inorganic materials in spintronics devices. Radically new spintronics functionalities, unavailable with conventional inorganic materials, could stem from the interface between ferromagnetic (FM) and molecular materials, giving rise to the so-called “spinterface” field. In this article, we review the fundamental concepts, recent experiments, and perspectives in this fast rising field, where the functionality is brought from the bulk to the ultimate downscaled device: the interface. The article shows how spin-dependent hybridization at the FM metal/molecule i…
Excited state absorption spectra of dissolved and aggregated distyrylbenzene: A TD-DFT state and vibronic analysis
2017
Made available in DSpace on 2018-12-11T17:33:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-07-21 Federación Española de Enfermedades Raras Ministerio de Economía y Competitividad A time-dependent density functional theory study is performed to reveal the excited state absorption (ESA) features of distyrylbenzene (DSB), a prototype π-conjugated organic oligomer. Starting with a didactic insight to ESA based on simple molecular orbital and configuration considerations, the performance of various density functional theory functionals is tested to reveal the full vibronic ESA features of DSB at short and long probe delay times. UNESP-Universidade Estadual Paulista POSMAT-Graduate Pr…
Metallization of the Na 14 Cl 13 Cluster
1994
The structure and energetics of multiple-excess-electron alkali halide clusters Na14Cl14-n, (1 ≤ n ≤ 6) is studied by ab initio calculations using norm-conserving pseudopotentials and local-spin-density-functional theory. Analysis of various electronic properties (Kohn-Sham one-electron eigenvalue spectra, ionization potentials, participation ratios of Kohn-Sham orbitals), as well as multiple F-center formation energies, suggests that these clusters can be characterized as Nan(NaCl)14-n having a "phase-separated" metallic part NaI. The Na14Cl9 (or Na14Cl9+) cluster exhibits a face (surface) segregated metallic Na5 (Na5+) overlayer, the stability of which is demonstrated by a molecular-dynam…
Confinement effects for ionic carriers in SrTiO3 ultrathin films: first-principles calculations of oxygen vacancies.
2010
One-dimensional confinement effects are modelled within the hybrid HF-DFT LCAO approach considering neutral and single-charged oxygen vacancies in SrTiO(3) ultrathin films. The calculations reveal that confinement effects are surprisingly short-range in this partly covalent perovskite; already for film thickness of 2-3 nm (and we believe, similar size nanoparticles) only the surface-plane defect properties differ from those in the bulk. This includes a pronounced decrease of the defect formation energy (by ∼1 eV), a much deeper defect band level and a noticeable change in the electronic density redistribution at the near-surface vacancy site with respect to that in the bulk. The results als…
Hydrogen adsorption on the ZnO $(1\bar{1}00)$ surface: ab initio hybrid density functional linear combination of atomic orbitals calculations
2014
Hydrogen atoms unavoidably presented in ZnO samples or thin films during their synthesis considerably affect electrical conductivity. Results of first principles hybrid functional linear combination of atomic orbitals calculations are discussed for hydrogen atoms incorporated in bulk or adsorbed upon non-polar ZnO (1¯ 100) surfaces. The energy of H incorporation, atomic relaxation, electronic density redistribution and modification of the electronic structure are compared for both surface adsorption and bulk absorption. It is shown that hydrogen forms a strong bonding with the surface O ions (Eads = 2.7eV) whereas its incorporation into bulk is energetically quite unfavorable. Hydrogen adso…
The electronic structure of zircon-type orthovanadates: Effects of high-pressure and cation substitution
2012
The electronic structure of four ternary-metal oxides containing isolated vanadate ions is studied. Zircon-type YVO4, YbVO4, LuVO4, and NdVO4 are investigated by high-pressure optical-absorption measurements up to 20 GPa. First-principles calculations based on density-functional theory were also performed to analyze the electronic band structure as a function of pressure. The electronic structure near the Fermi level originates largely from molecular orbitals of the vanadate ion, but cation substitution influence these electronic states. The studied ortovanadates, with the exception of NdVO4, undergo a zircon-scheelite structural phase transition that causes a collapse of the band-gap energ…
Synthesis and characterization of copper intercalated ZrTe3
1997
Abstract Electrochemical copper intercalation in ZrTe3 yields the new metallic ternary phase CuxZrTe3 with a maximum stoichiometry of x = 1.9. The charge is balanced by filling the σ∗ antibonding Te p bands, as monitored by XANES spectroscopy. The reaction is accompanied by an increase in the a lattice dimension of 9%. This observation is explained by theoretical calculations.
Imaging Symmetry-Selected Corner Plasmon Modes in Penta-Twinned Crystalline Ag Nanowires
2011
International audience; Using dual-plane leakage radiation microscopy, we investigate plasmon propagation in individual penta-twinned crystalline silver nanowires. By measuring the wavevector content of the light emitted in the substrate, we unambiguously determine the effective index and the losses of the mode propagating in these structures. The experimental results, in particular, the unexpectedly low effective index, reveal the direct influence of the nanowire crystallinity and pentagonal structure on the observed plasmon modes. By analogy with molecular orbitals of similar symmetry, the plasmon modes are also determined numerically in good agreement with the observed values. We further…
Simulations of the substitutional sites of Cr3+in LiNbO3from molecular orbital models
1992
Abstract The location of Cr3+ center in LiNbO3 crystals, is analysed from two types of molecular orbital (MO) calculations using MS-LSD and DFT-LCGTO methods. The optimization of the geometries according to the total energies of Cr3+ center at the two sites are presented.
Formation of an intermolecular charge-transfer compound in UHV codeposited tetramethoxypyrene and tetracyanoquinodimethane
2010
Ultrahigh vacuum (UHV)-deposited films of the mixed phase of tetramethoxypyrene and tetracyanoquinodimethane $({\text{TMP}}_{1}{\text{-TCNQ}}_{1})$ on gold have been studied using ultraviolet photoelectron spectroscopy (UPS), x-ray diffraction (XRD), infrared (IR) spectroscopy, and scanning tunneling spectroscopy (STS). The formation of an intermolecular charge-transfer (CT) compound is evident from the appearance of new reflexes in XRD (${d}_{1}=0.894\text{ }\text{nm}$ and ${d}_{2}=0.677\text{ }\text{nm}$). A softening of the CN stretching vibration (redshift by $7\text{ }{\text{cm}}^{\ensuremath{-}1}$) of TCNQ is visible in the IR spectra, being indicative of a CT on the order of $0.3e$ f…